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About this book

This book presents original, peer-reviewed research papers from the 4th Purple Mountain Forum –International Forum on Smart Grid Protection and Control (PMF2019-SGPC), held in Nanjing, China on August 17–18, 2019. Addressing the latest research hotspots in the power industry, such as renewable energy integration, flexible interconnection of large scale power grids, integrated energy system, and cyber physical power systems, the papers share the latest research findings and practical application examples of the new theories, methodologies and algorithms in these areas. As such book a valuable reference for researchers, engineers, and university students.

Table of Contents

Frontmatter

Analysis, Operation, Protection and Control of AC/DC Hybrid Power Systems

Frontmatter

A Novel Loss of Excitation Protection Principle for Synchronous Condenser Based on Leading Rate

There is a fundamental difference between loss of excitation protection of synchronous condenser and generator. The low excitation limit of synchronous condenser is very low, which is close to leading reactive power when full loss of excitation occurs. Loss of excitation protection may maloperate when synchronous condenser operating under low excitation limit. Moreover, the power angle cannot be applied to constitute protection criterion. The stepped characteristic curve is adopted by the existing loss of excitation protection of synchronous condenser which resulting in protection dead zone. Under high system voltage condition, the existing protection may refuse to operate when partial loss of excitation occurs. A novel loss of excitation protection principle for synchronous condenser based on leading rate is proposed in this paper. The stator side plane and the rotor side plane are constructed respectively by using stator internal potential and excitation voltage. The characteristic curve based on hyperbolic function is proposed to avoid the dead zone. The leading rate detector is proposed to distinguish partial loss of excitation and normal regulation under high system voltage condition. In addition, blocking criterion is introduced in this paper to prevent the maloperation of leading rate detector when sudden increase of system voltage occurs. The novel loss of excitation protection reliably operates when partial loss of excitation occurs under high system voltage condition. The reliability and sensitivity of loss of excitation protection is substantially improved. The PSCAD simulation results verify the inadequacy of existing protection and the superior performance of novel protection principle .

Hong Cao, Zexin Zhou, Huanzhang Liu, Zhi Zhang, Wenrui Cai, Xingguo Wang, Dingxiang Du, Jianmin Chen, Zhiyong Qiu

Research on the Screening of Multiple Contingency and Its Failure Probability Assessment Technology in Natural Disasters

It has become a common consensus that the blackout defense framework has been extended to the early warning of natural disasters. The generation of multiple contingencies and their probability assessment in natural disasters are the basis of risk assessment and preventive control of power system. Firstly, the generation method of multiple contingencies which takes into account the disaster simultaneity and spatial correlation is discussed. And the failure probability assessment method based on the coupling relationship between the transmission lines is proposed. Secondly, according to the characteristics of narrow transmission channels which is concerned by dispatcher, a failure probability correction method for narrow transmission channels is proposed by classifying related towers of transmission channels. Then, based on the designed severity prediction coefficient index, a method of screening multiple contingencies is proposed. Finally, an example of a provincial power grid is given to illustrate the effectiveness of the proposed method .

Kang Chang, Yan Huang, Changyou Feng, Qifeng Xu, Chen Yu, Haohao Wang, Taishan Xu

Application of Big Data Technology in Protection Channel Interruption Analysis and Breaker Defect Identification

Microcomputer protection indicated the protection device enter the intelligent era. Over years’ operation, a huge amount of data has been accumulated. Unfortunately, mass data has not been used effectively. The development of Internet technology brings protection into information age. Two typical applications are presented in this paper. One is abnormal protection channel interruption analysis; the other is breaker defect identification. Combining the data of the Protection and Fault Recorder Management System (PFRMS) with the data of the Communication Network Management System (CNMS), abnormal interruption analysis of the protection channel is studied in this paper. It effectively extracts the channel anomaly events that need to be focused on by the protection engineer. As for breaker defect, the characteristics of each time link in the fault isolation process are analyzed. The wavelet transform is used to capture the separation moment of the contact. The arc extinguishing time is analyzed to evaluate the arc extinguishing chamber. By cluster analysis, each time duration of fault isolation is calculated, the abnormal points differ from others can be found out easily, which means there is an abnormality in the secondary circuit of the breaker.

Maoran Zheng, Jiang Yu, Xiaobing Ding, Xianjun Li, Kai Wu, Jianwen Liang

Discussion of Power System Operation Risk Control Technology in Natural Disasters

It has become a common consensus that the blackout defense framework has been extended to the early warning of natural disasters. Due to the spatial and temporal distribution characteristics of natural disasters’ evolution, and fault uncertainty induced by natural disasters, it is urgent to extend the safety and stability analysis of power system based on deterministic criterion to the operation risk assessment, to extend traditional safety and stability control based on deterministic scenarios listed in three-defense-lines to risk control. In this paper, several key technologies in the field of disaster prevention, namely fault probability assessment, contingency set generation and screening, operation risk assessment and risk control decision-making, are reviewed firstly. Secondly, the risk control framework which is compatible with traditional three-defense-lines and suitable of natural disasters characteristics is discussed. Then the improved method of improving the mentioned key technologies is proposed under the risk control framework.

Kang Chang, Ming Zhao, Chen Yu, Jun Guo, Haohao Wang, Taishan Xu

Research on Energy Protection of DC Distribution Line

Compared with the AC distribution network, the DC distribution network can absorb various new energy sources more efficiently, which is one of the important development direction of future research. However, due to the poor ability of the power electronic equipment to withstand the fault current. It is very important to identify the fault area by using the transient information within a few milliseconds. Line protection technology is very important to the safe and reliable operation of DC power distribution network. Based on the fault analysis and simulation of the current DC distribution line, the current supplied near the converter side is much larger than the short circuit current provided by the line. There is energy between the internal and external fault. In order to characterize this difference, studied by using the energy difference method to determine the internal and external fault lines. A 5 layers Db wavelet transform is applied to the fault current of the DC distribution line, using low frequency the square of wavelet coefficients and to characterize the stationary current energy band in the time window. The proposed protection scheme is tested in RT-LAB, and the test results show that the energy protection scheme can accurately determine the fault section under different transition resistances and different fault locations.

Jiandong Duan, Zainan Li, Qing Yang, Hao Li

Synchronous Condenser Site Selecting Method for Reducing the Trip-off Risk of New Energy Generators

Focusing on the problem of new energy units tripping under power grid disturbance, a synchronous condenser site selecting scheme in the new energy sending system based on quantitative evaluation method is proposed in this paper. In this method, the quantitative evaluation index of reducing the new energy trip-off risk when the synchronous condenser applied to the network is calculated. In the index, the economic loss of new energy generators trip-off and the probability of grid faults is considered. And then according to the quantitative index, the priority of synchronous condenser sites is determined. Finally, the effectiveness of the method is verified by an actual power grid example.

Yu Wang, Fusuo Liu, Haifeng Li, Xuelian Wu, Yuqiang Hou, Xuemao Zhao

A Rapid Power Flow Analysis Method After UHVDC Fault Considering the Control Strategy of Automatic Equipment

The unbalanced power caused by ultra-high voltage direct current (UHVDC) fault may lead to the overload of transmission section or violation of busbar voltage in local power grid. In serious cases, it may lead to cascading faults or large-scale blackout. In order to accurately simulate the power flow distribution after large-scale power shortage and determine the validity of disposal strategy dealing with serious fault, a rapid power flow analysis method after fault considering the control strategy of automatic equipment is proposed in this paper. Considering the influences of automatic equipment to power grid operation situation on different time scales, the control strategy of power system stability control devices, the primary frequency control, automatic generation control (AGC) and automatic voltage control (AVC) is simulated. The active power of the generator and load at each stage is determined. The active power of transmission section and voltage of busbars under large-scale unbalanced power can be determined rapidly for the disposal strategy optimization. Simulation results based on actual power grid show the effectiveness and viability of the method.

Junjun Yang, Wei Xu, Shaofeng Liu, Xiancheng Ren, Xiaotong Xu

Research on Equivalent Power Model of UHVDC Converter Station Under Large Disturbances

Compared with high voltage direct current (HVDC) transmission, ultra high voltage direct current (UHVDC) transmission has more advantages obviously, which can perfectly satisfy the power requirements in China. In order to simulate and analyze the electromechanical process of large power grid. it is necessary to establish an accurate power model of UHVDC converter station. Firstly, according to the measured data of Yin-Dong DC commutation failure in 2011 and “6.14” Tian-Zhong DC blocking and simulation data based on PSCAD, the operation mechanism of UHVDC system and the output characteristics of active power and reactive power of UHVDC converter station under large disturbance is analyzed in detail. Then, based on event-driven ideas, an equivalent power model is proposed. Finally, based on PSASP software, the accuracy of the new model is validated by comparing with the measured result and the results of quasi-steady state model, the presented model in this paper is more accurate in describing the power characteristic of UHVDC converter under large disturbances.

Xiaolu Deng, Qian Chen, Haoqing Xiong, Lei Huang, Na Qiu, Qi Zhang

Research on Protection Strategy and Scheme of DC Distribution and Consumption System

Combing demonstration project of medium and low voltage DC distribution and consumption system in Suzhou, protection configuration scheme and fault location method for DC distribution system is studied. First, according to the grid structure, the protection areas of DC power distribution and consumption system are partitioned. Next, based on the fault characteristics of DC power distribution system, the protection configurations of each protected area are proposed. Finally, according to the characteristics of DC loop system, the protection criterion and fault location method are presented. The comprehensive fault location method based on differential protection and networked multi-point information is proposed. The correctness of protection strategy and fault location method is verified by RTDS.

Tonghua Wu, Wei Dai, Xindong Li, Yuping Zheng, Weicheng Ma, Xinyao Si

Over Excitation Limiter Oscillation Analysis and Damping Measures for ALSTOM Excitation System of Nuclear Power Unit

This paper analyzes the over excitation limiter (OEL) simulation model of the ALSTOM P320 V2. excitation system used by nuclear power generators in China. The way of OEL output received as input to the main loop is presented for studying on the OEL oscillation occurred at an actual Nuclear Power Plant. The oscillation phenomenon is reproduced in time domain simulation and the oscillation mechanism is revealed by frequency domain root locus analysis. The concept of critical gain of the over excitation limitation control loop of ALSTOM excitation system is proposed, and the tuning range of the main loop differential time constant is recommended. The feasibility and correctness of the damping measures on OEL oscillation are verified by field test at a real nuclear power unit.

Jiaping Ye, Jiang Wei, Qiang Liu, Feng Chen, Shaoqun Song

An Architecture Design of Distributed Intelligent Power System Stability Control System

This paper comprehensively considers the demand of the future power grid and the current power grid for the stability control system. Starting from the main links of the security and stability control systems such as communication, information and terminal, and finally establishes a distributed intelligent stability control system architecture based on the terminal interconnection. Key technologies such as node redundancy, collaborative work, network topology, and terminal access are also described.

Xiong Chen, Changpo Song, Yonghua Chen, Kaiyang Zhu, Shiguang Xu, Xiaolei Qu, Liangmin Zhong

Key Parameters Analysis of Sub-synchronous Oscillation Caused by Interaction Between Full-Converter Wind Turbines and AC Systems

A small disturbance math model of direct drive wind turbine including phase-locked loop (PLL) and voltage feed-forward control is established in the paper, and the dynamic impedance analytical expression under dq axis is derived. Based on the analysis method of frequency-equivalent impedance, it is found that the impedance has negative resistance (negative real part) characteristics in the sub-synchronous frequency band. Key control parameters and their characteristics which influence stability are analyzed.

Yuliang Wan, Song Xiang, Ling Zhu, Zhao Ding, Fusuo Liu, Xin Liu

Research on the Station AC Bus Fault-Crossing in Hybrid Half-Wavelength System

VSC-HVDC is a good way for new energy to access large power grids. It is used as a “third-terminal” to access half-wavelength transmission system to achieve AC-DC hybridization. However, AC bus in DC terminal has a short-circuit fault will lead the appearance of over-current in DC system and over-voltage along the AC system. In order to reduce the impact of the fault, a method of accessing a current limiting module at the DC bus is proposed. The current limiting resistor makes capacitor voltage attenuate over-damped and non-oscillating, and limits the over-current. Finally, the simulation proves that the module can effectively improve the fault traversal capability of the system.

Huaxin Wang, Xiaodan Shi, Bin Lu, Ke Li, Xiangli Deng

An Analytical Method of Determining Transient Stability Margin Considering Unbalanced Fault Factors

Maintaining the transient stability of the power system is very important for the stable and safe operating. This paper presents an analytical method of determining transient stability margin quantitatively using protection information for multi-generator system. First, the additional impedance of unbalanced fault is calculated by positive sequence equivalent rule. Based on the complementary cluster center of inertia-relative motion, the multi-machine system is equivalent to a one-machine infinity-bus system. Then, through the piecewise models of generator angles, the analytical expression of the equivalent fault clearing angle and the transient stability margin are obtained. Furthermore, the analytical stability margin is put forward to quantize the transient stability after fault occurred with the acquisition of the protection information, and the effects of fault location and fault clearing time on the stability margin under unbalanced faults are analyzed. Finally, four-machine two-area system is used as test system to investigate the effectiveness and accuracy of the proposed method.

Jiuliang Liu, Tong Wang, Zengping Wang

The Adaptability Assessment and Online Decision-Making for Strategy of Stability Control Systems Involving Multiple Types of Security and Stability Issues

Affected by artificial experiences and coverage of typical operating situations, the strategy of stability control system faces huge mismatch risk. It is difficult to effectively deal with complex and serious faults, such as multiple faults or successive faults. The method of adaptability assessment and online decision-making for strategy of stability Control Systems is proposed to involve multiple types of security and stability issues. Operating status of stability control devices is obtained to correct RTU data and improve the accuracy of operating conditions. Structural modeling is realized for strategy of stability control system to identify the on-duty strategy. Then, static security, transient security and dynamic stability analysis will be performed according to the on-duty strategy. A coordinated stability control strategy is constructed for the design of UHVDC and new energy characteristics to deal with the potential security and stability problems of power grid under large-scale DC transmission of new energy. When the control amount of strategy is insufficient or mismatched, the online decision-making of the preventive control considering the fluctuation characteristics of new energy power is realized by AC/DC coordinated control means. The proposed method is proved to be fast and effective through the analysis of a practical power grid example.

Jingjing Ruan, Wei Xu

A Simple Equivalent Method of HVDC System and Study on Resonance Characteristics of the System

This paper try to take a simple equivalent method to analyze the frequency impedance characteristics of the HVDC system which is a nonlinear time-varying system. As verification, the induced harmonic on the DC line from the AC line located in the adjacent corridor is analyzed. According to the frequency impedance characteristic of the HVDC system, the harmonics interference from the nearby AC lines located in different positions can be predicted. The simulation results are basically consistent with the prediction, which proves that the simplified model can help us study the sensitivity of a HVDC system to different frequency harmonics.

Qinglei Zhang, Jiangtao Li, Yicong Chen, Qing Wan, Jieyu Chen, Di Peng

Optimization of Transient Voltage Preventive Control of Receiving-End Power Grid Considering Start-up Unit Measures

With the rapid development of ultra-high voltage direct current construction, the replacement effect of conventional power supply at the receiving-end power grid is intensified, and its insufficient reactive power support capacity has become an increasingly serious problem. In order to solve the problem, an on-line optimal decision method for transient voltage security prevention control of the receiving-end grid considering start-up unit measures is proposed. A stage-by-stage optimization strategy is adopted to first switch the reactors and capacitors, then to adjust the reactive power of the units, and finally to start up units. The heuristic algorithm based on the control performance index and the parallel computing platforms are used to meet the computing speed requirement of the online system. The transient voltage control performance indexes of the reactors/capacitors and the reactive power adjustable unit measures are established according to the voltage sensitivity for the weakest transient voltage monitored bus. And the transient voltage control performance indexes of the start-up unit measures are established according to the electrical distance between their high-voltage side buses and the weakest transient voltage monitored bus. The effectiveness of the proposed method is verified by a case study of an actual receiving-end power grid.

Xiaoqin Xia, Shaofeng Liu, Yanhong Bao, Xiancheng Ren, Junjun Yang

Research on Control System-Level Hardware-in-the-Loop Experimental Verification Platform Based on Componentized Reconfiguration

The characteristics of China ultra-high-voltage AC/DC power grid change significantly after the ultra-high-voltage project’s operation. The system protection is proposed by State Grid Corporation of China (SGCC) which is supposed to meet the operation’s need of the district power grid such as several technological innovations. The comprehensive verification, effectiveness and reliability of the system protection are very important to ensure the security and stability of power grid. In this paper, a construction scheme for control system-level hardware-in-the-loop experimental verification platform based on component reconfiguration is proposed. By combing the function and the structure of the experimental devices, optimizing the layout of interface modules and the inter-station communication devices, the disadvantages of traditional “one experiment, one platform” including large workload, low recycled, long development period and difficult maintenance are effectively improved. The technical solution has been applied in the System Protection Laboratory of SGCC, and the effectiveness has been verified by the hardware-in-the-loop real time simulation experiments. This work is supported by State Grid Corporation of China.

Xuan Liu, Yuqiang Hou, Jianbing Xu, Feng Xue

Analysis and Simulation of Transient Response of MAF-PLL with PLC

Phase-locked loop (PLL) is a vital technique for grid-connected inverters to achieve synchronization, and is requested to detect accurately the frequency and phase when inverters are synchronized. Moving average filter PLL (MAF-PLL) improves the filtering capability of synchronous reference frame PLL (SRF-PLL), but causes a phase delay of 180° in the PLL control loop, which affects the transient performance of MAF-PLL. To improve the transient response of the MAF-PLL, a phase-lead compensator (PLC) is cascaded in the MAF-PLL control loop to overcome shortcoming of MAF-PLL. The effectiveness of the proposed PLL is verified by simulation and numerical analysis.

Jiahao Wang, Huan Pan, Chunning Na

HVDC Commutation Failures Detection for Security and Stability Control Based on Local Electrical Quantities

The commutation failure of high-voltage direct current (HVDC) transmission system will have a huge power impact on the AC system. It is necessary to accurately identify the commutation failure of the HVDC for the security and stability control device (stability control device). At present, the stability control device which has already been applied in engineering for HVDC identifies the commutation failure of HVDC depends on the command of DC control and protection system, and there is a certain risk. The valve side current of converter transformer and the DC current of valve group that can be directly collected by the engineering are studied. Starting from the self-demand of the stability control device, new HVDC commutation failure and continuous commutation failure criteria are proposed based on the original commutation failure protection principle. Also, RTDS test verification was carried out.

Dongyang Liu, Zhukun Li, Haibo Xu

Research on AVC Substation Control Strategy of Synchronous Condenser

With the voltage levels and capacity of UHVDC system increasing, synchronous condensers are installed in converter station to provide subtransient and transient voltage support, also it’s required to consider the demand of steady-state reactive power. Therefore the automatic voltage control (AVC) system plays a vital role in the operation and function of synchronous condenser. In this paper, taking a receiving-end condenser station for example, the overview of AVC substation is introduced, then the control strategy and switching logic between different working modes are analyzed using experimental data. Finally the impedance between the station bus and infinite power system is derived, and a method to calculate the maximum regulating value of bus voltage by synchronous condensers under steady state is proposed.

Yingfeng Zhu, Qing Yan, Ming Li, Xiangrong Meng

Flicker Source Detection in Power Distribution Systems

It is a key issue for both utility and users to detect out the flicker source in order to solve the contradiction between them and mitigate the disturbance. This paper proposed a new detection method for flicker source in complex power distribution systems with DG. First, generalized S-transform is applied in complex signal processing, for getting the features of multi-source flicker and extracting the flicker envelope. Then, inter-harmonics from relevant flicker sources are gotten with the envelope signal by FFT. Latter, independent criterion for detecting flicker source are constructed according to different inter- harmonics. Finally an optimized comprehensive criterion is constructed with support vector machine method. The test results in a power distribution system in Jiangsu Province, China show that the proposed method has good performance of correctness in case of multi-source flicker condition.

Ganyun Lv, Qiyu Wu

A Commutation Failure Prediction Criterion Based on Feasible Region Theory

Aiming at the problem of commutation failure often occurring in high voltage direct current (HVDC) system, the shortcomings of existing commutation failure prediction criterion applied in the commutation failure prevention control strategies are analyzed. The basic reason of commutation failure is studied in the way of mechanism. Combined with feasible region theory which is widely used in power system and many other fields, a concept of commutation feasible region is put forward in this paper which can improve the accuracy of commutation failure prediction to some extent. Both commutation feasible regions in the pre-fault and post-fault parameter spaces are described in definition. The relative parameters are analyzed in each parameter space. In order to make it more intuitive and convenient, the method for constructing the section of commutation feasible region in the control parameter space of regular HVDC system is proposed. In the end of the paper, the validity of the proposed theory is verified by means of simulation carried out on the PSCAD/EMTDC platform.

Yuan Zeng, Yan Li, Yiming Yang, He Zhang

Research on Insulator Fault in Haze Days Based on Particle Swarm Optimization

In this paper, the leakage current data is collected through experiments, and the particle swarm optimization algorithm is used to analyze the development process of pollution flashover. The artificial contamination test is designed reasonably. The leakage current samples under five different pollution levels are collected, and the unbiased threshold method is selected. The leakage current signal is denoised, and the eigenvectors of the frequency components are extracted by wavelet packet analysis and empirical mode decomposition. By comparison, the energy of the leakage current increases as the degree of contamination increases. On the basic of summarizing the current research on pollution flashover mechanism, a least squares support vector machine algorithm based on particle swarm optimization of leakage current frequency component is proposed to detect the contamination degree of insulator. This method is compared with traditional particle swarm optimization algorithm. The effect of this algorithm in processing the feature quantity of frequency components extracted by EMD method is better than that of processing the feature quantity of wavelet packet analysis.

Kexin Zhang, Xijin Guo, Yunzhi Xu

Analysis of the Influence of System Characteristics on Ultra-Low Frequency Oscillation

The ultra-low frequency oscillation phenomenon is not only related to the characteristics of the governor of the hydropower unit, but also closely related to the system characteristics. Based on the detailed analysis of the hydroelectric governor model, a simplified analysis model of the ultra-low frequency oscillation of the power grid is proposed. The influence of the system inertia and load frequency adjustment effect coefficient on the ultra-low frequency oscillation is analyzed. The frequency response model of the hydropower and thermal power hybrid grid is constructed. Through the analysis of the ultra-low frequency oscillation characteristics under different proportions of hydropower, the influence of system inertia on ultra-low frequency oscillation is further clarified. The correctness of the conclusion is verified based on the simulation in a simple system.

Xuelian Wu, Zhaowei Li, Guang Xu, Fusuo Liu

Analysis of the Moment Inertia of Energy Storage System Under Different Control Modes

In power system, the moment of inertia is the main index to measure the frequency change rate of power grid. The bidirectional power control of energy storage system improves the frequency modulation capability of power grid, which means that the energy storage system provides additional moment inertia for power grid. However, there is still a lack of relevant theoretical methods based on how to characterize the equivalent inertia of energy storage system. According to the motion equation of the rotor, the expressions of inertia of the energy storage system under different control modes are analyzed. According to the influence of the moment of inertia on the frequency variation of the power grid, the optimal frequency regulation method of the energy storage system is given. The simulation and analysis environment is established to verify the influence of different control modes of energy storage on the moment inertia and frequency change rate of power grid.

Zhaohui Qie, Hui Huang, Wei Li, Zhaowei Li

A Balance Control Strategy for H-Bridge Cascaded Energy Storage Converter Battery Pack

H-bridge cascade structure is a typical way for energy storage equipment to achieve high voltage and large capacity. It is difficult to ensure that each battery operates in accordance with the same charge-discharge curve because of the difference of the parameters of each battery. It is very easy to cause overcharge and over discharge of single battery and reduce the life and performance of energy storage equipment. Aiming at the above problems, a balancing control strategy of cascaded H-bridge energy storage converter is proposed. Firstly, the working principle and internal energy transfer mode of cascaded H-bridge energy storage converter are explained. Secondly, the working state of each battery pack and the sub-module electricity are calculated by the current charge state and average charge-discharge curve of each battery pack. Capacitance voltage command value is combined with sorting algorithm and nearest level approximation method to realize the sub-module capacitance voltage stability and make N−1 battery pack work according to the average electric curve (N is the number of H-bridge modules). Finally, in the MATLAB/Simulation software, a small simulation model is built to verify the feasibility of the control algorithm and provide a reference for large-capacity multi-module storage.

Xiaohong Wang, Xiaochun Mou, Ruohan Zhao, Kai Hou, Ning Zou

A Situation Awareness and Fault Recovery Decision-Aid System for UHVDC

Given the large capacity that UHVDC system involved, once fault occurs, a huge impact to the power system along with problems such as power flow overrun, insufficient backup capacity, frequency drop and even cascading failure is expected. To prevent this, research on solutions and precautions of UHVDC faults is needed. In this paper, a comprehensive system with applications such as situation awareness, risk pre-assessment, preventive control, real-time monitoring, fault process tracing and fault recovery decision aiding is presented. This system has been deployed in provincial centers in China, played a crucial role in numbers of UHVDC failure cases and lay a firm foundation for the later research on related area.

Jinjun Lu, Mingze Gao, Xin Shan, Yi Wang

The Fault Record Analysis Display Technology Based on Mobile Terminal

With the development of modern technology, mobile technology is widely used on many electric fields as its convenience and low-cost advantages. Since the grassroots electricians are equipped mobile terminals for higher efficiency, the electric enterprises reinforce the construction of mobile system and professional software application demand is increasing. In this paper, the fault record analysis display technology is raised to solve the concurrent request, data compression, information extraction and high-performance curve drawing when application runs in multi-client mode. Practice has proven that the application with adaptive display technology satisfy the requirements for relay protection routine maintenance and fault analysis which effectively increase the efficiency of electric operation and management.

Lei Fan, Huaning Zhang, Qiannan Chen, Meng Li, Xiang Ji

SVC Emergency Control Study on Continuous Commutation Failure

DC continuous commutation failure always a difficult issue that threaten the safe and stable of power grid. In order to increase the dynamic reactive power of the system, reduce the probability of continuous commutation failure. This paper focuses on the effect of SVC to reduce the failure of DC continuous commutation. Firstly, it theoretically analyzes the working principle of SVC, and the SVC control strategy and parameter setting in detail. Secondly, based on the commutation area method, proposing a continuous commutation failure prediction method. Then the SVC emergency control strategy is developed based on that. Finally, the proposed SVC emergency control strategy is verified in the HVDC CIGRE model. The results show that the method has certain correctness and effectiveness in reducing the risk of DC continuous commutation failure.

Jie Lei, Xiaobo Tang, Fusuo Liu, Yu Wang, Ling Zhu, Mengyang Zhao

Data Window Selection Method Applied to Sampled Value Differential Protection

In this paper, the characteristics of the saturation current waveform are analyzed, and the instantaneous value of the differential current and the instantaneous value of the braking current and the rate of change of the differential current and the rate of change of the braking current are compared in the case of CT saturation. A data window of each wave cycle selection method for sampled value differential protection is proposed, and the real time digital simulation (RTDS) test is carried out. The test proves that the differential protection used this principle is not affected by the system frequency, the current non-periodic component and the CT transfer characteristic. The sampled value differential protection can operate quickly for the internal fault, and cannot operate reliably for the external fault. In the case of complex transferring faults, the rapidity and reliability of the differential protection operation can still be guaranteed. The data window selection method is accurate and reliable, and the sensitivity of the sampled value differential protection operation is improved.

Fengguang Wang, Hang Lv

Active Splitting Strategies Based on Severe Faults of Hybrid AC/DC Power Systems

Recently, the development of the ultra-high-voltage hybrid AC/DC power systems brings not only positive effect such as large-scale resources’ optimal allocation to release the intense resource situation in China, but also negative one such as great challenges to the safe and stable operation of power systems, which brings great strength to the whole power systems. Especially with the larger scale and capacity of DC feeding to the same receiving end, one AC fault in the power system may cause cascading AC/DC failure, which may be worse cause the simultaneous commutation failure of multiple DC lines. The simultaneous commutation failure of multiple DC lines will increase the risk of large capacity loss in the power systems. To maximally guarantee the power supply of local important load, active splitting is deemed to be an effective method. In this paper, the receiving-end grid with multiple DC lines feeding to is considered. Firstly, the research results of active splitting strategies got by the researchers are listed, and the different technologies of active splitting strategies are also mentioned. Secondly, the scenarios in which transient instability of the whole power system happen in the severe AC and DC cascading failure are analyzed. One is the instability of the whole system caused by DC blocking of multiple DC lines, along with the invalid out-of-step splitting, the other is the failure of stability control device which is deal with the problem of transient instability of local power grid. To avoid the local important loads going instability with main power systems when the extreme severe faults happen, the general framework of active splitting strategies is designed. The framework is according to the specific instability characteristic of the scenarios mentioned before, and in the meantime, the trigger criteria of active splitting strategies are also proposed, as well as the chosen principles of the active splitting surfaces. When the transient instability of whole power system occurs, the active splitting strategies take responsibility for the safe and stable operation of the local important loads by splitting the decided active splitting surfaces triggered by the active splitting signals (including the capacity of DC blocking provided by the active splitting primary control stations, the signals of line voltage and power angle provided by wide-area measurement system (WAMS)), and along with the additional emergency control (usually including the load shedding) which is taking advantages of the WAMS. Finally, the active strategies are confirmed to be effective by verifying in an actual power system, and the simulation results turn out that the active splitting strategies with specific selection of active splitting surfaces and emergency control can be utilized to deal with the severe faults in ultra-high-voltage hybrid AC/DC power systems.

Yanjun Wang, Jingliao Sun, Zhaowei Li, Weizhen Sun, Jihong Li, Xuelian Wu, Jing Zhang

Controller Parameters Optimization Design in VSC-MTDC System

The control system is significant for steady and dynamic response of voltage source converter multi-terminal DC (VSC-MTDC) system. The VSC-MTDC system is first built and small signal models of different control modes are deduced. Then the converters in VSC-MTDC system are classified into two types. As for VSCs connected to active networks, design procedures for PI control parameters in outer loop and inner loop are given respectively. Design procedure is also given for VSCs connected to passive networks when AC voltage control is adopted. Simulation results, carried on PSCAD\EMTDC, are presented under various operating states.

Ting Wang, Guobing Song, Lishuai Yin, Haijing Zhang, Yanli Zhang

AC & DC Flexible Transmission and Distribution Technology

Oscillation Between VSC-HVDC and AC Grid: Phenomena, Analysis and Solution

Several oscillation events happened between VSC-HVDC system and the AC grid in recent years, which may result in the outage of VSC-HVDC. To understand the oscillation and find solutions, this paper concentrates on the mid- and high-frequency oscillation between VSC-HVDC and the AC grid. The 1270 Hz oscillation happens in China Southern Power Grid (CSG) is firstly reviewed. Then the physical and mathematical mechanism of the oscillation is analyzed. Analysis result show that as it’s hard to eliminate the negative-real-part of VSC impedance due to the long control delay in VSC-HVDC systems, the occurrence of oscillation is the inherent characteristic of VSC-HVDC connected to the main power grid. Fortunately, the oscillation can be damped by changing the grid impedance or optimizing the VSC impedance. The influencing factors are analyzed and then the solution approaches are discussed. The analytical results are verified through simulation in PSCAD/EMTDC.

Hong Rao, Changyue Zou, Weiwei Li, Shukai Xu, Yan Li, Xiaobin Zhao, Jun Chen, Yuebin Zhou

Analysis of the DC Overvoltage Caused by the Blocking of MMC Inverter Station

In this paper, the mechanism of DC overvoltage is discussed, which caused by block fault in the converter station connected with the active network, and the dynamic process of DC voltage is analyzed in detail according to the equivalent circuit and the operating state of sub-module. Moreover, the DC overvoltage caused by the blocking of converter station is studied with the consideration of different blocking time. It is found that the development process of DC overvoltage is independent of fault time, and the virtual overvoltage is generated in steady state mainly contributed by the defect of simulation software that the disconnection of circuit breakers could not be truly reflected in the simulation software. The study of DC overvoltage can provide recommendation for the safety and stability of practical project and the design of insulation grade and protection. Finally a two-terminal MMC-HVDC simulation model built on PSCAD/EMTDC shows the effectiveness of the proposed analysis method.

Yuetong Zhao, Yuanyuan Sun, Rui Yin, Shanshan Wang, Bing Zhao, Shanmeng Qin, Panbo Yang

A Practical Method to Calculate the AC-Side Short-Circuit Current of MMC-HVDC

With more and more MMC-HVDC connected to the AC network, the short-circuit current contributed by converter station should be taken into account when the short-circuit fault occurs at the AC-side. In this paper, the characteristics of short-circuit current contributed by MMC are analyzed and a simple and convenient method to calculate the fault current is proposed. Study shows that the characteristics of short-circuit current depend on the control method that MMC adopted. The development of short circuit current can be divided into transient-state and steady-state stage according to whether the controller responds completely or not. Considering the margin of IGBT, current limiters are set both in inner and outer controller. It can limit the bridge arm current and avoid overload. Therefore, AC-side current will change within the limit value. A practical method for the short-circuit current calculation is proposed based on the controllers and limiters. Through this method, both the symmetrical and asymmetrical fault short-circuit current can be calculated after the controllers enters steady state. The analysis in this paper shows that MMC can be equivalent to the current source at steady-state and participate in the calculation of AC system short-circuit. Finally, the accuracy of the proposed method is verified in the PSCAD simulation.

Shanmeng Qin, Yuanyuan Sun, Rui Yin, Bing Zhao, Shanshan Wang, Yuetong Zhao

Reliability Analysis Based on MMC Valve Operating Conditions in HVDC System

As the essential part of high voltage direct current (HVDC) system, modular multi-level converter (MMC) can be controlled properly, which is related to the safety and stability of the whole system. In actual operation, the influence of different working conditions on the core components is not the same. In this paper, the influence of different working conditions on electronic components is analyzed based on the working principle of MMC. When establishing the system reliability model, considering different backup strategies, k/n (G) model and Gamma distribution are adopted respectively. The effects of two different backup strategies on the system are compared and the effects of the redundancy of submodules on the reliability are analyzed. If the component failure rate is determined, the increase of redundant modules can improve the reliability of the system. Under the same redundancy rate, the cold standby strategy improves the system reliability more obviously.

Mengyi Li, Yue Wang, Chengzhi Zhu, Jiazhuo Xuan, Chaoliang Wang

A Control Strategy of Suppressing Offline for Large-Scale Wind Power Generators Caused by DC Commutation Failure

With the rapid operation of the external power transmission system of the UHVDC wind power base, the frame of the sending AC power gird cannot be effectively strengthened. The DC commutation failure causes the problem of large-scale wind power generators offline to restrict the UHVDC cross-regional transmission of new energy seriously. Therefore, firstly, based on Gansu Qishao DC wind power transmission to the grid, the mechanism of DC commutation failure causing wind generators to separated from the power grid is analyzed. Then, an control strategy of suppressing offline for large-scale wind power generators caused by DC commutation is proposed. According to Qishao DC wind power transmission system, simulation verify the feasibility and effectiveness of the strategy.

Xuemao Zhao, Yiding Jin, Bijun Li, Jian Liang, Zhao Ding, Ling Zhu

Control Scheme of Modular Multilevel Converter Under Unbalanced Grid Voltage

In a modular multilevel converter (MMC) system, the grid asymmetry on AC side will cause problems like non-sinusoidal 3-phase current on AC side of MMC converter, fluctuation of active and reactive power, and large fluctuation of double frequency current and voltage on DC side. In order to solve these problems, a differential-based positive and negative sequence separation is proposed, which has limited delay and high precision after grid asymmetry occurring. Then the fluctuation form on AC-side power is analyzed according to the instantaneous power theory. Secondly, in conjunction with the control objectives of suppressed negative sequence current and instantaneous active power, theoretical analysis on the bridge arm circulating current is carried out, which obtains the expression of given current in the inner loop under the corresponding control objectives. Finally, MMC simulation model is established based on PSCAD/EMTDC, then the simulation verification for two control objectives under asymmetric grid is carried out respectively.

Tonghua Wu, Xiaohong Wang, Weicheng Ma, Xindong Li, Dehui Chen, Jiayong Zhong

Research on Converter Topology and Control of Co-phase Traction Power Supply System Based on MMC Topology

With the rapid development of railways, high-quality power supply and safe operation of trains have received extensive attention. Aiming at the problems of electrified railway power quality and electric phase separation device, combined with the status quo of engineering transformation, converter reliability, economy and redundant backup of the power supply system. Summarized and compared the advantages of MMC topology in the traction power supply system. Proposed a co-phase power supply system based on modular multi-level converter (MMC) and traction transformer. When the converter works normally, the power is obtained from the three-phase power grid, the three-phase power is converted into two-phase power through the traction transformer, the two-phase power is respectively connected to two single-phase MMC to become direct current, the direct current is converted into single-phase alternating current for the locomotive through the single-phase MMC; when the converter fails, due to the traditional traction transformer structure is retained, the conventional power supply mode can be operated to achieve the redundancy backup purpose of the system. Then, analyzed the DC capacitance voltage control, circulation suppression, control strategy and modulation strategy suitable for MMC topology during normal operation. Finally, obtained some research conclusions of the co-phase power supply system based on MMC topology and traction transformer.

Ming Gao, Xiaohong Wang, Xiaochun Mou, Houcheng Chu

Design and Application of Centralized Instrument Transformer Measuring System in Series Compensation System

This paper analyzes the requirements of the high-voltage platform measuring system of the series compensation system. Through the analysis of the platform of series compensation system, this paper study’s the noise source and route of TA measuring system on the platform and puts forward a centralized TA measuring system. The system uses signal processing and photoelectric conversion module based on low-power CPLD and reliable redundant power supply. The module features in centralized TA measuring system are also introduced. The system was successfully applied in the Canadian series compensation project.

Chang-yin Zhu, Jian Wu, Yuan Chang, Yu-chan Zhao, Xiang Li, De-chang Wang, Gui-ping Hu

Reliability Analysis of MMC Based on Junction Temperature Calculation in HVDC System

Modular Multilevel Converter (MMC) valves are widely used in high-voltage direct current (HVDC) power transmission projects, and their reliability is one of the research priorities which is closely related to IGBT. Excessive junction temperature is one of the important causes of IGBT damage. Therefore, it is necessary to further study the key factors affecting IGBT junction temperature. Firstly, based on the temperature-sensitive parameter method, the thermal impedance model of IGBT is established, and the parameters of thermal impedance model under different working conditions are analyzed. Secondly, based on the numerical calculation model, the losses of the core component IGBT module of the converter valve under different working conditions are calculated. Then, the junction temperature of the IGBT is calculated by the thermal network method. Finally, the junction temperature of IGBT in the actual engineering of the MMC converter valve is calculated theoretically, the loss and junction temperature under different working conditions are analyzed.

Taiyuan Yin, Yue Wang, Zhuling Li, Qiao Kang, Chengzhi Zhu, Jiazhuo Xuan

Adaptability Analysis of Differential Protection for Series Transformers of Unified Power Flow Controller

The series transformer is one of the core components of the Unified Power Flow Controller (UPFC). The series transformer has a special primary structure and special system operating characteristics. Taking the simulation system of the actual UPFC project as an example, this paper discusses the factors that may affect the sensitivity and reliability of the series transformer differential protection under various faults. Combined with the simulation results of the typical faults in the series transformer, the longitudinal differential protection is analyzed. Reflecting the new problems that arise when series transformers have various types of faults, the adaptive analysis of the differential protection is formed. This paper also discusses the relationship between valve control protection and AC relay protection of series transformers from the perspective of protection equipment.

Yu Cui, Qiaogen Gu, Yi Wu, Zhongmin Sun, Ye Wang, Xiao Cheng

IGBT Open-Circuit Fault Diagnosis and Location of MMC Sub-module

Modular multilevel converter (MMC) has a high probability of IGBT open-circuit fault, while reliability is one of the main challenges facing MMC. The sub-module fault is one type of common faults of MMC; the timely diagnosis and location is a great concern for the operational stability of MMC-HVDC. In this paper, in view of the single-tube open-circuit fault of MMC, a method for fault diagnosis and location is proposed. The method is based on sampling the output voltage of single arm which reduced computation complexity. With the purpose of fault diagnosis and location, the sub-module fault characteristics were analyzed, then according to the diagnosis rules to achieve the fault status identification of a bridge arm. A simple sequential process was applied to realize fault location. Based on PSCAD/EMTDC, a high-voltage DC simulation system with an 11-level modular multilevel converter was built. The final simulation confirms that the proposed schemes can achieve the timely sub-module fault diagnosis and location so that the stable operation of MMC-HVDC can be guaranteed.

Peiwen Qi, Wendi Zheng, Xinchong Wu, Xiangyong Zeng

Analysis of the AC Side of Modular Multilevel Converters Under Asymmetric Arm Impedance Conditions

The arm parameters of the upper and lower arm of modular multilevel converters (MMCs) are not always symmetric in the practical projects. In fact, there will be some differences inevitably. Under this unbalanced condition, there is an interaction between the internal circulating current and the AC side current. A theoretical analysis of MMCs under the asymmetric arm impedance conditions is carried out to find the characteristics of the AC side output current. In this case, a DC component will appear on the AC side and the expression for the bias current is achieved. The DC component will lead to a DC-bias problem on transformers. A simulation model is built with PSCAD/EMTDC, which verifies the influence on the AC side of MMCs under the asymmetric arm parameter conditions.

Xinchong Wu, Wendi Zheng, Peiwen Qi, Tenglong Zhou, Jianxiong Nie

Small-Signal Modeling of Series Resonant Dual Active Bridge DC-DC Converter

The extended description function method is applied on the small-signal modeling of Series Resonant Dual Active Bridge DC-DC converter. The closed-loop control system is designed based on the small-signal model. The established model is controlled by switching frequency. Finally, the Simulink software in MATLAB is used to simulate the small-signal model. The experimental results show that the closed-loop control system has good dynamic and steady-state performances, which can prove that the small-signal model obtained by the extended description function method is accurate.

Kai Hou, Yanwei Liu, Zhigang Wang, Liya Zhu, Jiquan Yang

Development and Application of FACTS Technology

Over the past few decades, FACTS technology has been developed rapidly. And various FACTS controllers have been widely used in the world. This paper presents the development and status of FACTS technology, and introduces the applications of FACTS controllers, especially the typical domestic applications. The key technologies such as system design, control strategy design, equipment development, etc. are summarized. Then, in view of the demands and challenges of FACTS controllers, combined the trends of innovative technologies, the development trend and application prospect of FACTS technology are forecasted.

Hui Yan, Xiong Zhan, Jianchun Cao, Yongsheng Fu

Fault Monitoring and Location for the Metallic Return Line in VSC-HVDC Grid

The metallic return lines of ±500 kV Zhangbei VSC-HVDC grid are voltage-free during normal situation, which make it difficult to realize fault monitoring by conventional methods. Furthermore, the metallic return lines are mounted together with the pole lines, either as single-loop or double-loop, which will cause wave impedance discontinuity and traveling wave refraction problem. As a result, traditional Time Domain Reflection (TDR) method is not suitable for the fault monitoring of the metallic return lines. According to the characteristics of the metallic return lines of ±500 kV Zhangbei VSC-HVDC grid, this paper presents a fault monitoring system and waveform comparison analysis method based on differential mode TDR method. The system applies differential mode pulse signal to monitor the fault, and uses waveform comparison method to eliminate the waveform reflection caused by inherent parameter discontinuity of the line, thus highlight the fault characteristics. The simulation and field tests show that the system and method can adapt to the wave impedance discontinuity of metallic return lines in Zhangbei VSC-HVDC grid. The method has high reliability and sensitivity for fault monitoring, and the location accuracy is better than 300 m.

Yulin Chen, Jianfeng Zhang, Xiaoyang Yu, Jie Zhang

DC Micro-grid Voltage Control Strategy Based on Discrete Consensus Algorithm

Due to the uneven distribution of virtual resistance and line impedance in the DC micro-grid, the traditional droop control has the contradiction between current sharing and voltage regulation. In this paper, the droop control based on the discrete consensus algorithm is adopted. Each power generation unit adopts adjacent communication, and the reference value of the DC bus voltage is corrected according to the mean value after the iterative of the system voltage, thereby compensating for the voltage drop caused by the droop control. The photovoltaic (PV) cell adopts the maximum power tracking (MPPT) control. The battery adopts the constant voltage control with current threshold, which can keep the DC bus voltage stable, and the outlet current is prevented from being too large to shorten the service life of the battery. Stable operation of the DC micro-grid is realized. Finally, the PV/battery DC micro-grid model is built in Simulink. When the environmental conditions and load change, the micro-grid can ensure the DC bus voltage constant and the active power balance, which verifies the effectiveness of the proposed control strategy.

Ke Jia, Jinfeng Chen, Bin Yang

Submodule IGBT Parameters Estimation Scheme in Modular Multilevel Converters with Reduced Voltage Sensors Based on Kalman Filter Algorithm

Considering the reliability of modular multilevel converter (MMC) closely related to key component parameters, a novel parameter estimation method is proposed for insulated gate bipolar transistor (IGBT) of submodule (SM) in MMC. The relationship between the switch status and the voltage of submodule is analyzed and the model of the bridge arm voltage is established. Kalman filtering theory is introduced against the measurement noise of the bridge arm data from sensors. Under the linear minimum variance criterion, the model of the IGBT parameter monitoring information in MMC submodule is established to obtain the IGBT parameters from each submodule in the bridge arm. The substantial reduction in the number of voltage sensors improves the system reliability and decreases its cost and complexity. This method can also effectively eliminate the influence of sensor noise. Finally, the effectiveness of the proposed technique is validated via a PSCAD/EMTDC simulation analysis of MMC-HVDC.

Tenglong Zhou, Wendi Zheng, Qidong Xu, Xiangyong Zeng, Jianxiong Nie

Safety Operation of Active Distribution Network and Coordinated Control of Transmission and Distribution Networks

Frontmatter

The Intelligent Early Warning System for the Gale-Induced Transmission Tower Fault Probability

Gale is one of the important reasons causing transmission tower collapse. Therefore, precisely prediction and early warning of the gale which may cause the transmission tower fall down can decrease the loss to power grid at utmost. In this paper, non-linear stepwise regression (NLSR) method is used to forecast gale in the power grid. To avoid the single statistical method errors, the back-propagation (BP) artificial neural network is used to optimize the results intelligently. Further, we consider the gale-induced tower failure rate, and couple it to the forecast model. Finally, we establish an intelligent gale-induced transmission tower fault warning system to predict the probability of accident. The simulated result shows that the accuracy of the model in predicting gale-induced transmissions tower fault probability is good.

Nailong Zhang, Huazhao Wang, Yang Liu, Jianjun Liu, Lujun Zhang

Optimal Allocation and Sizing of Shunt Capacitors in Unbalanced Radial Distribution Systems: A Comparative Study

A comparative study on the problem of optimal capacitor allocation and sizing in unbalanced radial distribution systems (URDSs) is presented in this paper. The comparison is performed between three different sensitivity-based indices, which are utilized for selecting the optimal locations of the three-phase capacitors. Those indices are: index vector (IV), combined loss sensitivity factor (CLSF) and voltage stability index (VSI). For the comparison purpose, the capacitors’ sizes are obtained by implementing particle swarm optimization algorithm (PSO). Two main aspects are considered in this comparison: (i) the number of locations for capacitors to be installed at, and (ii) the type of the three-phase capacitors (balanced or unbalanced three-phase capacitors). The optimization problem is basically a minimization of three objective functions, namely: power loss, voltage deviation and voltage unbalancing. The comparative analysis is executed on the 25 bus unbalanced system and then simulation results are discussed and evaluated.

Rabea Jamil Mahfoud, Yongjie Zhong, Nizar Faisal Alkayem, Yonghui Sun

Forest Fire Tripping Probability Prediction System Based on Partial Mutual Information Method

High voltage transmission lines are mainly built in deep forests. However, forest fires have occurred frequently in recent years. At present, the power grids mainly monitor and warn forest fire, but they lack the longer time scale for the prediction of forest fire. Based on the partial mutual information method, the local fire risk level model is established, and then the forest fire tripping probability prediction system is established for the transmission lines of the power grid. On September 1, 2017 wildfires trip accident happened in some regions of Guangdong Province, and then the forest fire tripping probability in Guangdong Province is forecasted. The results show that the system can predict the accident area with a high probability of fire tripping about 1 day in advance, and the application of the system can provide longer time prediction information of forest fire tripping for the safe operation of power grid transmission lines.

Yang Liu, Dongdong Yang, Jianjun Liu, Nailong Zhang, Lujun Zhang

An Adaptive Protection Scheme Based on Fault Components of Phase Current Difference for Positive Distribution Networks

In order to solve the difficulties brought by the integration of distributed generations and their unpredictable outputs, this paper proposed an adaptive current protection scheme. The fault components of phase current difference have demonstrable differences under normal and fault conditions, especially for unsymmetrical fault. Accordingly the magnitudes of these fault components could be adopted to evolve an instantaneous overcurrent protection. Moreover, these fault components could also be used to distinguish fault types, and this feature could be developed as a definite time overcurrent relay. Zoning strategy is proposed as a supplement for symmetrical fault. Simulation results on a 10 kV distribution system have verified that the proposed scheme could identify the fault type adaptively and located the fault at the same time, which is capable to eliminate the influence of distributed generation integration on current protection settings. With an adaptive relay setting and large reach, the fault could be reliably cleared with this protection scheme no matter where the DG locates and how the output power of the DG changes.

Wenhao Zhang, Yinghao Zhang, Chengshan Huang

Dynamic Coordination Optimization for Active Distribution Network Considering Energy Storage System

The optimal scheduling of active distribution network(ADN) is an important guarantee for the realization of economic and safe operation, and the core technology to actively manage distributed energy resources (Mao et al. in Autom Electr Power Syst 43(8):77–85, [1]). This paper establishes a dynamic optimization model for active radial distribution network based on Distflow, whose control variables include the output of distributed generation (DG), charge and discharge power of energy storage system (ESS), capacitor bank (CB) switching, output of static var generator(SVG) and transformer tap position. The model aims to minimize the network loss, adopts second-order conic relaxation (SOCR) to convexify the original problem and employs commercial solvers (MOSEK, CPLEX, etc.) to obtain operation moment and capacity of each device in the scheduling cycle. Simulation tests on the modified IEEE 33-node system show that the algorithm proposed can effectively reduce active loss, improve energy efficiency and lower network operation cost.

Min Cao, Honglin Wang, Kemeng Li, Zhensheng Wu, Lianbiao Sun

Research on Voltage Control Strategy of Distribution Network Based on Model Prediction Technology

With the development of the economy and the improvement of people’s living standards, energy has become an increasingly indispensable substance. The large-scale development and utilization of fossil energy has caused problems of energy crisis and environmental pollution. In order to solve these two problems, it is necessary to develop and utilize renewable energy sources, and access distributed power sources in the distribution network to form an active distribution network. The active distribution network contains a large number of distributed power sources, energy storage units and reactive power compensation equipment. Although it provides more convenience for voltage and reactive power regulation of the distribution network, the intermittent and volatility of renewable energy sources will also be Its voltage has a big impact. In order to solve the voltage dip and overvoltage problem of active distribution network, a new active distribution network voltage control strategy is proposed by using model prediction control technology. Inaccurate system modeling is reduced by establishing active distribution bus voltages, distributed power supplies, and energy storage device prediction models. With the minimum adjustment cost as the control target, the second-order cone relaxation method is used to optimize the action behavior of each control device. Finally, the IEEE33 node simulation example is built on the matlab simulation platform. The results show that the proposed voltage control strategy has good control effect and robustness.

Qing Wang, Jingwen Ai, Huaying Zhang

The Application for Automatic Voltage Control Technology Considering Energy Storage in Regional Power Grid

Compared with the traditional energy, energy storage power stations using emerging clean generation technology have the advantages such as peak regulation, voltage regulation, and suppressing power fluctuation of grids. Due to its advantages of eliminating voltage overstepping and optimizing reactive power, automatic voltage control (AVC) system has been widely used in power grid control system in recent years. In this paper presents a voltage coordination control technology for regional grid energy storage stations considering the reactive margin, and elaborates the principle and the implementation of the control scheme. The practical application of the site shows that the control strategy of this scheme is feasible and effective, and it can effectively exert the advantages of control voltage and optimal reactive power of the energy storage power station, which is conducive to improving the stability and power quality of the power grid.

Tianhua Chen, Dawei Xu, Luo Yang, Jianhua Chen, Lei Du, Lufei Xu

A Method of Extracting and Recognizing Discharge Current of Bird Hazard Hidden Danger Based on Wavelet Transform

Bird damage is one of the important reasons that affect the safe and stable operation of overhead transmission lines. The main cause of bird-caused hidden-danger discharge is the pollution flashover of insulator caused by bird manure. Using traveling wave positioning system to monitor and identify potential bird hazards before bird hazards cause overhead transmission line faults is an important means to prevent bird hazard faults. Therefore, how to identify and extract the Bird-caused hidden-danger current has become the key to the accurate operation of traveling wave positioning and early warning system. In order to solve this problem, a method of extracting and recognizing discharge current of bird hazard hidden danger is proposed in this paper. Based on the principle of phase-shift subtraction and wavelet transform, this method subtracts the total current of normal-working phase from the total current of hidden-discharge phase, and then identifies and extracts the characteristic of hidden-danger current by wavelet transform, so as to realize the recognition and early warning of bird-caused hidden danger discharge. In this paper, the ATP electromagnetic transient simulation platform is used to simulate the bird hazard potential discharge and the wavelet analysis of the potential discharge current is carried out with MATLAB, which proves the effectiveness and feasibility of the above method.

Binbin Rao, Yanglin Li, Jingsheng Zhang, Zhaoyang Zhang, Jing Hu, Longwu Zhou, Fan Li, Jiaxin Yuan

Dynamic Voltage Control Technology Research of PV Power Plant Based on Inverter Phase Modulation

By analyzing the current situation of reactive power control in new energy power plants, the principle of reactive power control with inverter phase modulation is expounded, and a structure of reactive power control system for photovoltaic power plants based on GOOSE communication protocol is introduced. The deployment of the actual system and the field test of the dynamic reactive power control system of photovoltaic power station show that the system can realize the rapid local control of reactive power, and the response time is less than 30 ms, which meets the requirement of dynamic reactive power response time of reactive power compensation device, and has the promotion conditions of engineering application.

Hucheng Li, Yubo Yuan, Liudong Zhang

An Intelligent Distributed Feeder Automatic Strategy for Active Distribution Network and Its Implementation

With the large-scale integration of distributed generations (DGs) and microgrids, the distribution network has been transformed from a traditional single-supply network to a multi-supply active distribution network. Thus, the traditional fault location technology becomes unsuitable for the new active distribution network, which only considers the single power flow direction of the system with breakers and the local self-healing strategy without power balancing. This paper proposes an intelligent distributed feeder automation implementation method for active distribution network. Based on real-time neighborhood message sharing, self-healing and high-speed real-time communication technology, an intelligent fault isolation strategy is introduced for rapid fault locating, isolating and self-healing in active power distribution network without relying on the primary station. The intelligent distribution automation terminal based on SOC chip is also developed and applied to implement this strategy, which provides an automatic solution for rapid fault location, isolation and self-healing of active distribution network.

Guo Hu, Hai Wu, Peng Jin, Kuo Tan, Feng Huang

Multi-point Optimized Access Method of PVs Considering Peaking Effect

The paper has proposed a multi-point optimized access method of distributed generators aiming at peak shaving of feeder in distribution system. First of all, typical daily load curve of the feeder has been analyzed to get different peaking need of different seasons during operation. Based on this, multi-point optimized access model has been established, taking optimized peaking shaving effect and penetration of renewable energy as the objective, and taking no power returned and capacity limit as the constraint condition. Genetic algorithm has been used to solve the problem. The result shows that it is more refined to consider operation condition during the optimization. And the dual objectives can result in an optimized capacity interval for reference during project implementation.

Yuwei Zhang, Yang Yan, Wenjun Li, Jian Yuan, Hua Jiang

Partial Discharge Monitoring of Dry Distribution Transformer Based on Grid Search Scheme and Characteristic Analysis

In this paper, a partial discharge location model of power transformer is proposed, and the solution method of partial discharge fault location equation is studied. The location accuracy analysis considering time difference, sensor position and sound velocity measurement error satisfying different probability distributions is also presented. A new location algorithm based on grid search is proposed, the algorithm has high positioning accuracy, but its calculation is too large. Through the simulation analysis of MATLAB programming, compared with the previous algorithm, the improvement measures for the new algorithm are proposed.

Yang Chen

Ubiquitous Power Internet of Things Technology

Frontmatter

Design of Fault Location Scheme for Distribution Network Based on Edge Computing

With the implementation of the “three-type two-network, world-class” strategy, the requirements for building a ubiquitous power Internet are proposed. In order to further improve the accuracy of fault location in distribution network, this paper designed a fault location scheme for distribution network based on edge computing. Through the information technology and intelligent technology such as edge computing, artificial intelligence, mobile internet, etc., the power distribution terminal completed the fault diagnosis of the distribution network “on the spot”. The design scheme divided the distribution line into several responsibility segments. Each responsibility segment was composed of one distribution terminal or feeder terminal as the collection terminal. The remaining distribution terminals in the responsibility segment served as the collection terminal and accepted the management control of the collection device. After a short-circuit fault or single-phase ground fault occurred in the distribution network, the aggregation terminal issued a control command, requesting the collection terminal to feed back the short-circuit fault alarm signal or the fault current waveform data, and analyzed the waveform data through the artificial intelligence algorithm to achieve fault location. The feasibility of the fault diagnosis decision bit was verified by the field application of the oscillating fault indicator. The design scheme could reduce the resource occupation of distribution automation station fault processing and improve the fault location efficiency of distribution automation station.

Minyu Li, Shuhua He, Xiangwei Chen, Yifan Wang, Jiafang Huang

Intelligent Park Load Scheduling Optimization Method Considering Heat-Power Linkage

Aiming at the problem that the load peak-to-valley difference of the power system distribution network is high and the load volatility is large, this paper proposes an intelligent park demand response (DR) day-to-day scheduling strategy considering hybrid heating mode of heat-power linkage (HPL). Firstly, based on the analysis of the original load classification of the intelligent park, the intelligent park user load demand is divided into load replaced by heat (LRH) and load irreplaceable by heat (LIRH), and the energy consumption mode with flexible scale thermoelectric ratio is proposed. Then the minimum variance of the side load curve of the distribution network is taken as the goal, and the optimization model of the intelligent park load scheduling considering the HPL is constructed. The DR strategy considering the HPL is proposed. Finally, the rationality of the proposed scheme is illustrated by the calculation example. The results show that the load peak-to-valley difference and volatility are reduced, and the side load flexibility of the distribution network is enhanced.

Zesheng Hu, Jun Lu, Xingxing Wang, Zhiqiang Xu, Gangjun Gong, Yun Wang

Research on Self-adaptive Strategy of Video Communication in Power Transmission and Transformation Project

According to the existing problems in the construction site of transmission and transformation project, an on-site monitoring and control system of power transmission and transformation project was designed. The on-site video is transmitted back to the project headquarters through the wireless network of the service provider. However, due to the unstable bandwidth of the wireless network and the weak signal strength of the scene, the real-time transmission of the video may cause a long transmission delay and a video jam. In order to ensure the flow degree and integrity of video transmission, a video optimal transmission method based on one-way queuing delay was proposed according to the data stream characteristics of bidirectional transmission of monitoring and control system. At the receiving end, we detect the network congestion according to unidirectional queuing delay and estimate the bandwidth according to the state of the buffer and improve the TFRC algorithm to make it suitable for this system and ensure more stable data transmission by adaptively controlling the bit rate. The experiment shows that the optimize transmission method can efficiently evaluate the state of the network, accurately control the bit rate change, and provide technical support for the on-site monitoring of the power transmission and transformation project.

Yingwei Yi, Feng Lin, Yu Ye, Lifu He, Jiabin Zou

Development of Transformer Terminal Unit Based on Virtual Technology

In order to conform the development trend of distribution network, the requirement of terminal need to have the ability of Internet of Things (IoT) is becoming more and more prominent. Firstly, the paper expounds the development trend of low-voltage distribution network and emphasizes the technical transformation of the transformer terminal unit. Secondly, it puts forward the software and hardware architecture of the transformer terminal unit which is suitable for the IoT. Then, it introduces the key technologies related to the transformer terminal unit. Finally, it analyzes the next stage of the work plan for the improvement of the function.

Cheng Zhou, Hai Wu, Guo Hu, Ji Zhang, Chenbin Zhang

Multi-scenario Application of Power IoT Data Mining for Smart Cities

Power IoT data will be an important data foundation for building smart cities, and IoT data has a broad prospect for deep mining. This paper analyzes the main needs of urban construction and the status of power Internet of Things data, and summarizes the overall demand of the smart city for the Internet of Things. It demonstrates the data support of the smart Internet of data mining from the two aspects of power consumption behavior and regional maturity assessment effect. Through case studies, electric power IoT data mining can provide decision-making basis for smart cities such as power planning, mature community management, municipal engineering, and residential life improvement.

Chen Li, Shen Jian, Zhang Min, Peng Qi, Hou Zhe

Cyber Security Technology of Power Systems and Cyber Physical Fusion Technology (Cyber Physical Power System)

Frontmatter

External Node Intrusion Detection Scheme Based on Node Trust Value of WSNs in AMI of Smart Grid

In order to ensure the safe and stable operation of smart grid, the intrusion detection scheme based on node trust value is proposed for external node attacks of wireless sensor networks (WSNs) in Advanced Metering Infrastructure (AMI). The scheme applies the positive-abnormal statistics of communication messages to calculate the trust value. In this paper, the node trust value calculation method is improved and the trust value is used to judge whether the node is invaded. The simulation results show that the scheme can effectively detect external node intrusion, and has higher detection rate and lower false detection rate.

Tong Weiming, Tong Chuntian, Jin Xianji, Li Zhongwei

Security Protection and Testing System for Cyber-Physical Based Smart Power Grid

With the development of the information and communication technology, power grid has developed from a traditional power equipment network into a heterogeneous cyber-physical system. The framework and security requirements of grid cyber-physical system are presented. Security risks of four layers are analyzed including perception layer, network layer, platform layer and application layer. Cyber-attacks are classified by attack form and attack target. Information security protection system and security testing system are proposed, and key technics are analyzed.

Luolin Zheng, Tiefeng Gao, Xiaofei Zhang

The Petri Net Based Probability Transfer Analysis of Cyber-Physical Power System Under False Data Injection Attacks

Since the physical equipment inside the substation may be uncontrollable due to malicious attacks, which affects the state estimation of the system and the reliability of related advanced analysis and decision functions, this paper models the substation system based on Petri net and analyzes the system under false data injection. The probability distribution characteristics of each device being attacked. Focus on the attack mode under the false data injection attack, Petri net provides a solid foundation for CPS modeling. We first describe the typical attack scenarios in the substation, Secondly, the Petri net is used to refine the important equipment in the cyber system, and based on the observed real-time attack events, attack graph is used to dynamically update the attack behavior probability. Finally, the optimal load control strategy considering node failure is proposed to comprehensively and evaluate the impact of false data injection attack, the results show that the probability distribution of equipment attack in substation under false data injection is consistent with Poisson distribution.

Xiaofei Zhang, Luolin Zheng, Rui Zhou

Design of Security Monitoring System for Power Dispatching Control Cloud Platform

At present, cloud computing, as a strategic emerging industry in China, has greatly promoted the development of informatization. Although State Grid Corporation of China’s regulation cloud construction is steadily advancing, there is no effective security protection in the face of illegal access, virtual machine escaping, abnormal operation traceability, etc. In this paper, a security monitoring system based on the cloud platform is designed to achieve the comprehensive real-time monitoring of cloud platform security events of the hosts, virtual machines and cloud management software, timely identify of security threats with early warnings, and guarantee the operation of the cloud platform in security, through the investigating and in-depth research on the security monitoring technology of key components of the cloud platform.

Ge Zhaoqiang, Li Huixun, Zhang Liang, Shao Lisong, Zhai Haibao, Liang Ye, Ge Minhui, Qu Gang

Research on Unified Identity Authentication System for New Generation Dispatch Control System

According to the characteristics of the human-machine cloud terminal in the new generation dispatch control system, this paper designs a unified identity authentication system by combining the existing dispatch digital certificate system, face recognition and other identity authentication methods, which effectively improves the reliability of local identity authentication. Also designed an identity label based on the national secret algorithm, when a user accesses an remote business system across domains, the identity label can be sent to the remote business system to prove his identity. It is no longer necessary to perform complex identity authentication again, which solves the problem of identity authentication of local users in the wide area network, and achieve wide-area identity authentication for users across the entire network.

Jing Wang, Ye Liang, Liming Wang, Lisong Shao, Ming Yang

Key Technologies in the Power Spot Market

Frontmatter

Decomposition Model Framework of Trading Volume of Cascade Hydropower Stations Under the Linking Mode of Medium-Long Term and Spot Market

The electricity market reform of China is in the transitional stage from medium and long-term market to spot market. At present, most provinces still focus on medium and long-term electricity trading. A few provinces, such as Guangdong, have begun to simulate spot market operation. At the present stage, how to link up the medium and long-term market with the spot market is a key technical problem to be solved urgently. Aiming at the decomposition and execution of medium and long-term transaction power of cascade hydropower stations, this paper proposes a model framework of transaction power decomposition under the mode of linking medium and long-term with spot market. In the first place, this paper presents two monthly trading power decomposition models according to different seasons. Then a daily generation planning method based on standard load curve is proposed to decompose the daily power. Finally, the proposed method is applied to a provincial power grid. The results show that the proposed method provides some ideas for the rational curve decomposition of transaction power.

Mengfei Xie, Maolin Zhang, Xiangrui Liu, Gaoquan Ma, Peishan He

Risk Assessment of PSC Under Peak-Valley TOU Price Policy Based on CVaR Method

The uncertainty of electricity price, such as the volatility in the spot market and the influence of the peak-valley time-of-use (TOU) electricity price on the load, are important factors in the loss of risk of electricity purchase and sale to power sales companies (PSC). In order to evaluate the impact of the above two factors on the risk loss of the PSC, this paper establishes a function for measuring the conditional risk loss of PSC based on the conditional value at risk (CVaR) theory considering the peak-valley TOU price. The established model considers both the price volatility of the electricity purchase side and the implementation of the TOU price policy, the demand price elasticity is used to obtain power consumption during peak, flat and valley periods respectively. The proposed model has been verified by the case studies. The results show that the implementation of the peak-valley TOU price policy can effectively reduce the risk of PSC and increase their revenue, and PSC can choose the appropriate price spread ratio or quantity to purchase to avoid risk.

Yaxin Li, Jungang Yin, Junfei Zhu, Lun Ye, Jiangang Yao

Optimal Deployment of Energy Storage for Providing Peak Regulation Service in Smart Grid with Renewable Energy Sources

With the increasing penetration of renewable energy generation (such as wind power) in the future power systems, the requirement for peak regulation capacity is becoming an important issue for the utility operators. Energy storage is one of the most effective solutions to address this issue. Under this background, this paper proposes a novel multi-objective optimization model to determine the optimal allocation capacity of energy storage in a thermal power plant for provision of peak regulation service in smart grid. To achieve this, we limit our study to a context based on the compensation mechanism performed in the auxiliary peak regulation market of northeast China. On this basis, an optimal energy storage allocation model in a thermal power plant is proposed, which aims to maximize the total economic profits obtained from peak regulation and renewable energy utilization in the system simultaneously, while considering the operational constraints of energy storage and generation units. A classical weighted summation technique has been used to deal with the bi-objective structure of the problem and a compound solution algorithm based on Generic Algorithm is employed to resolve the developed model. The effectiveness of the proposed methodology is examined based on a real-world regional power system in northeast China and the obtained results verify the effectiveness of our approach.

Dexin Li, Jiarui Wang, Haifeng Zhang, Chuanzheng Gong

Influence of Risk Favor on the Market Clearing of a Competitive Electricity Market

For a pool-based electricity power market, the bidding strategy of individual generators is a key factor that influence the market clearing price. In this paper, the profit function and risk indexes for individual generators are derived. The bidding strategies of generators are selected based on different preference of profit and risks. Three typical strategy, aggressive, normal and conservative, are chosen as the bidding strategy for analysis. Simulations results on different scenarios show obvious effects of bidding strategies on the market clearing results.

Shuhai Feng, Xuan Zhang, Yang Bai, Limin Cheng, Yu-Qing Bao, Mei Wu

Research on Equilibrium of Power Spot Market Considering Demand Response Strategy

In the context of the power spot market, an equilibrium model of power spot market based on locational marginal price is proposed in this paper. Firstly, the SCED model for market clearing ahead of day is established. Because the operation cost target in the power market is Multi-segment linear function, integer variables are introduced in order to achieve the linearization of the model. Afterwards, Lagrange multipliers of corresponding power flow equations in the model is used as the nodal price. In addition, the concept of electrical dissatisfaction is introduced on the load side. For each node load, a load response model is presented based on the goal reducing electricity cost and electrical dissatisfaction. Finally, the effectiveness of the power spot market equilibrium model is verified through the simulation of IEEE 39 nodes, and the effect of the transmission power limit on the nodal price and the influence of the capacity of participating demand on the response of load are analyzed in detail in the paper.

Wenxin Guo, Ruifeng Zhao, Bin Wang

Analysis of Electricity Price Affordability of Large Industry Consumers in Yunnan Electricity Market

Demand for electricity in high-energy-consuming industries is the dominant component of transaction volume in electricity market. Conversely, the price fluctuations in the electricity market have a close impact on its electricity demand. Analysis of its electricity price affordability is an important prerequisite for promoting the sustainable development of the electricity market and improving the market mechanism. Based on component analysis of industry consumers’ cost and benefit, this paper modifies the parameters affecting the consumer’s production cost according to the fluctuation of the electricity market transaction price and the market price of related products, then puts forward the analysis method of electricity price affordability of large industry consumers in Yunnan electricity market. Case study of the actual data in Yunnan electrolytic aluminum industry from January 2016 to June 2018 was carried out to verify the practicability of the method. The analysis of the electricity price affordability of industry consumers in the electricity market environment helps to identify reasonable appeals and excessive demands between the parties, and provides decision-making reference for market operation monitoring and mechanism improvement.

Xiangrui Liu, Maolin Zhang, Weiheng Li

Analysis of the Characteristics of Cross-Border Power Trade Network Based on Complex Network Theory

With the opening of the regional electricity market, the interconnection and interoperability of international power grids is constantly moving forward. In the face of increasing cross-border power commodity trade, social network analysis is widely used to analyze the structural characteristics of cross-border power trade networks, but traditional analysis only focuses on the topological structure of power trade network, lacks consideration of trade volume. Based on this, this paper uses complex network theory to establish a cross-border power trade weighted network for cross-border power trade along the “Belt and Road” region. In view of the trade volume in power trade, the weights of network links and nodes are taken into account. Then this paper improves the calculation method of aggregation coefficient and network structure entropy, and the characteristics of network structure such as degree distribution, aggregation and heterogeneity of cross-border power trade network are analyzed.

Kai Fan, Rong Fu

Power Trading Strategy Considering User Response Characteristics Under Incentive Conditions

China is now undergoing a major power section reform. On the electricity market side, the reform enables the power sale to be more market dominated. Thus for major power retailers, the needs of more flexible and economic sale strategies become bottlenecks to keep up with the market changes. In this paper, we target at incentive-based demand response scheme, and propose a power trading strategy considering load payback effect. We divide the power market as long-term market and day-ahead market. Then we develop a fine-grain power procurement and sale model considering both markets to maximize the profit of the retailer. Simulation from GAMS show the validity and effectiveness of the proposed model.

Xun Dou, Pan Zhang, Ping Shao, Yanmin Guo, Xin Zhang

Real-Time Generation Scheduling Model and Its Application Considering Deep Peaking of Thermal Power Units

With the large-scale access to new energy source and the difference between electricity peak and valley of mass consumption province increasing day by day, domestic demand for peak shaving has gradually increased. As the energy structure of china is not reasonable because of the installed capacity of thermal power accounting for a large part of the whole installed capacity and the shortage of peak power the power grid is suffering the difficulties of peak shaving. Faced with the peak shaving pressure of the domestic power grid, this paper deeply excavate the deep peaking capacity of thermal power units, analyze their operating characteristics. Based on the conventional optimization model, it introduces constrains such as the running time of the smooth peak output and the minimum peak peaking time, and improving the unit output range and climbing constraints on the basis of conventional optimization models to establish a real-time power generation plan optimization model considering the deep regulation of thermal power units. This paper carries out a case study base on the actual operation data of Guangdong power grid. The results of the case are in line with expectations and meet the actual operation requirements of the grid.

Yantao Zhang, Xiangyu Lǚ, Dexin Li, Jiarui Wang, Mengfu Tu

Operation, Protection and Control of Power Systems with High Penetration of Renewable Energy

Frontmatter

Voltage Online Assessment and Decision-Making Based on POPF with HVDC Transmission Capability and RES Fluctuation Consideration

Uncertainty and variability are the inherent factors of intermittent power resources such as wind and solar. With HVDC transmission system, a closely interconnected power system rather than a group of relatively independent regional grids is formed and transmitting energy continuously from resource redundant areas to the load centers. This paper proposed a voltage online assessment and decision-making approach based on probabilistic optimal power flow (POPF) with HVDC transmission capability and renewable energy source (RES) fluctuation consideration. Classification and permutation approaches are applied to the decision-making model for key nodes determination, which are closely related to the HVDC links. Voltage assessment is implemented by probabilistic approach and searching qualified voltage samples. Cigre HVDC Benchmark model with modified IEEE 9-bus 3-machine Benchmark Network is established for simulating in PowerFactory DIgSILENT Version 15.1, and the proposed algorithm is implemented with DIgSIELNT Programming Language (DPL) in the software package.

Hao-Tian Zhang, Kang Chang, Duo Geng, Cun Dong

Smart Grid Technology Standard System and Related Research

Frontmatter

Micro-grid Optimization Scheduling Based on Improved BBO Algorithm

The micro-grid system consisting of photovoltaic, wind turbines, diesel generators and micro gas turbines is studied, and a micro grid optimization model based on economic and environmental objectives is established. A biogeography-based optimization algorithm based on quantum optimization is proposed for this model. The quantum revolving door operation is introduced into the traditional BBO algorithm, which not only preserves the rapid convergence of the original algorithm, but also mitigates the shortcoming that it is easy to fall into local optimum due to precocity in the search process. The algorithm is applied to solve the micro-grid economic optimization problem and compared with traditional BBO algorithm and adaptive particle swarm optimization algorithm. The results show that it has higher convergence precision and faster convergence speed, and the obtained solution is better. The rationality of the proposed model and algorithm is verified.

Yunning Zhang, Kaixuan Kuang

Load Tracking Control of Air Conditioners Based on a Second-Order Equivalent Thermal Parameter Model

Considering an energy crisis and serious environmental problems, demand respond (DR) programs, including price-based DR and incentive-based DR, are designed to improve the stability of the power system. Direct load control (DLC) is one of effective incentive-based control methods relying on directly triggering the load reduction, which is relatively easy and inexpensive to implement. Due to the large electricity consumption and good heat storage capability, air conditioners are the important demand response resources. The accurate thermodynamic model of air conditioner can directly influence the effectiveness of control strategy. In this paper, an air conditioner control method based on the second-order equivalent thermal parameter (ETP) model is proposed, and the load-shifting potential by the DLC of air conditioning load is discussed. The reference signal is calculated for the air conditioners based on the peak-load-shifting requirement. Then an adaptive hill climbing (AHC) control method is designed for tracking the air conditioning load to the reference signal. The simulation results indicate that the proposed approach can achieve a guaranteed load curtailment by the DLC of the air conditioning load.

Ting Wang, Xiao Liu, Lixia Zhou, Beibei Sun, Mei Wu, Yu-Qing Bao

Line Loss Analysis and Reduction Method for Small Hydropower Embedded Distribution Network

The distribution system power flow during flood season and dry season varies greatly, due to the impact of the output fluctuation of small hydropower in different seasons. Hence, it is necessary to optimize and adjust the grid structure, operation mode and load level for the sake of distribution network loss minimization. A distribution network operation analysis method is proposed. Then the impact of different operation modes of small hydropower on the power grid is comprehensively analyzed. The integrated power and line loss management system and its theoretical line loss calculation module are used to verify the impact of different operation modes of small hydropower. Finally, the optimized solutions are effectively conducted to reduce the line loss.

BoJian Chen
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