The Proceedings of 2023 International Conference on Wireless Power Transfer (ICWPT2023)

The magnetic coupling resonant transmission method has been widely concerned due to its high transmission efficiency, reliability, convenience, and effectiveness. In this paper, the application of magnetic coupling resonance type wireless power transmission technology in the rocket power supply scenario is studied, and the influence of the operating frequency, the number of transmitter receiver coil turns and the transmission distance changes on the parameters and performance of the curved coupling coil is analyzed. The coupling structure model of the rocket ground Wireless power transfer system is established, and the scheme of curved coupler Wireless power transfer system for the Long March 8 carrier rocket is proposed, which is verified through simulation analysis.

An accelerator-based facility, such as an FEL injector, has stringent requirements on the quality of electron beam, and the electron beam is directly determined by beam injector, which is generally a source to provide driven beams with the energy of several MeVs. Since such space-charge dominated relativistic beams are sensitive and easy to be deteriorated during transportation, it is necessary to carry out online monitoring of beam quality under commissioning, so as to achieve accurate measurement of beam parameters such as beam spot size, beam emittance and beam energy spread, and beam current. The whole measuring facility is composed of magnetic components such as analysis magnet and quadrupole magnet. It is necessary to control and monitor the magnet current, and then display the data uniformly to the operating interface and feed back to the user through different control and measuring devices in the system. This paper introduces the basic principle of beam measuring device and the layout design of measuring system. Based on EPICS system and LabVIEW software, a distributed three-layer architecture control and measuring system is developed, which can realize feedback control, remote monitoring and signal acquisition. The whole system is stable and reliable in operation, convenient in use, high in beam parameter accuracy and accurate in calculation, which improves the efficiency of online monitoring.

Wireless intelligent sensors are being widely used in power system, which can perceive the measured information, transform the perceived information into an electrical signal and even conduct analysis and diagnosis. As one of the most important components in wireless intelligent sensors, radio frequency (RF) front-end module becomes more and more sensitive to electromagnetic interference (EMI) with the increasingly severe electromagnetic environment in high voltage and extra high voltage power equipment. Therefore, it is extremely vital to discuss the characteristics of EMI on the typical RF front-end module of wireless intelligent sensors. In the present work, the nanosecond electromagnetic pulse (EMP) wave was produced by high voltage nanosecond pulse generator and radiation antenna. Meanwhile, the electromagnetic model was built by the CST Studio, and the numerical simulation of the coupling and conduction voltages has been carried out. The coupling transient electromagnetic disturbance on the custom-designed RF front-end module was measured. The bent and impedance variation microstrip segments would receive more coupling energy during the radiation. This work should be of great benefit to understand the coupling mechanism under different conditions and explore the method of electromagnetic protection.

Magnetic resonance imaging (MRI) technology is the mainstream medical imaging technology today. The use of ultra-high static magnetic field strength (≥7T) can better improve the signal-to-noise ratio of imaging and bring clearer imaging quality. However, the inherent standing wave effect of the classic resonant cavity transmitting coil will cause B1+ field inhomogeneity and high SAR value. Studies have shown that high dielectric constant materials can effectively improve the standing wave effect, but there are problems such as difficulties in manufacturing and long-term stability. This paper proposes a method for measuring the dielectric constant of artificial electromagnetic materials based on the microstrip line resonance method, which improves the traditional method of using scattering parameters to obtain the dielectric constant of artificial electromagnetic materials in the induced near-field region, and can effectively reflect the artificial electromagnetic materials in the near-field region. By loading the artificial electromagnetic material on the 7T birdcage coil and comparing it with the birdcage coil without control material, its B1+ field has been doubled, compared with the artificial electromagnetic material B1+ field designed by the traditional measurement method. The artificial electromagnetic material structure designed by the microstrip line resonance method has a significant field regulation effect in improving the uniformity of the B1+ field in the induced near-field area through experimental verification, and has good clinical applicability.

Large-space wireless power transfer (WPT) technology can realize free space wireless power transmission while ensuring electromagnetic safety.However, the power transmission capability of the system is weakened by corresponding non-uniform weak magnetic field. To surmount these limitations, this paper proposes a novel power-enhanced large-space wireless charging system, which can achieve a wide spatial uniform magnetic field that can satisfy the safety requirements, and realize a stable output power of tens of watts across an extensive spatial domain through the relay energy conversion structure. The system design scheme and corresponding solution are introduced. The large-sized coils are compensated in segments to achieve uniform magnetic field. The compact relay energy conversion structure with both receiving and transmitting capabilities is analyzed. The energy of surrounding space is initially captured by the receiving coil in the relay structure and subsequently converted into higher frequency alternating current, seamlessly transferred to the transmitting coil in the relay structure, and ultimately transmitted to the receiving device. In this way, the transmission power can be improved through the two-stage energy conversion structure. The transmission characteristics of the system are derived and analyzed, confirming its effectiveness through simulation and experiment. The results demonstrate that the system can significantly enhance the transmission power capability under the electromagnetic safety standards. The experimental results show that within a space of about 25 m3, the system can be charged anywhere, and the charging power is about 18 W.

The accurate measurement methods for carbon emissions are critical in both incentivizing consumers towards energy conservation and emission reduction, as well as ensuring fairness in carbon emissions trading. The indirect carbon emissions are generated from user’s electricity consumption. The existing indirect carbon emission calculation method assumes that the carbon emissions per unit of electricity are the same at any nodes and any time in the power grid. Carbon flow calculation method could bridge this gap, however, it still need improvement when applying to large power grid. This paper proposed a practical indirect carbon emission calculation method by parallel computing the divided power grid, thereby significantly reducing the computational pressure. Furthermore, an effective Thévenin equivalent fitting technique is adopted to lessen the computational complexity in the transmission network. By clustering typical scenarios, the annual equivalent carbon emission intensity can be calculated for any node in the power grid. These calculated carbon emission factor can serve as substitutions for the traditional carbon emission factors. The case study proves this method for carbon emission calculation manages to strike a balance between computational complexity and acknowledging the spatio-temporal characteristics in carbon emissions.

The constant pitch variable speed control system based on permanent magnet synchronous generator is time-varying, nonlinear and strong coupling control system. The wind is strongly disturbed during operation, especially in the high wind speed area, the system is a nonlinear system with local positive feedback and instability. To address these issues, a sliding mode control theory based on interference observation is proposed. On the one hand, a new variable exponential reaching law is adopted to greatly reduce the pulsation of sliding mode variable structure controller; On the other hand, the disturbance observer is used to compensate for the influence of aerodynamic torque, eliminate the instability of the system itself, and achieve stable operation of the unit above the rated wind speed. Finally, the rationality of the design scheme and the robustness of the controller are demonstrated through simulation.

An improved fractional-order sliding-mode voltage controller is proposed for the problems of system jitter and high total harmonic distortion (THD) of grid-connected current in the model predictive direct power control (MPDPC) strategy for PV grid-connected systems under external disturbances. The algorithm uses fractional order calculus theory in the DC side bus voltage outer loop, firstly, constructs fractional order non-singular fast terminal sliding mode surface function to weaken system jitter and improve system dynamic performance; then constructs fractional order double power exponential convergence law and introduces weighted integral gain and saturation function, which can effectively avoid the increase of switching gain when the system is not in the sliding mode phase and improve system control accuracy; finally, designs The new fractional-order voltage loop controller is applied to the PV grid-connected system. The research results show that the improved fractional-order sliding-mode voltage controller can meet the basic requirements of the grid-connected PV system, effectively suppress system jitter, reduce the grid-connected current THD, and improve the robustness and dynamic performance of the system.

Pumped storage power station has the functions of peak loading, valley filling, frequency modulation and emergency backup, etc. When the pumped storage power station is running under the working condition of the motor, the static frequency converter (SFC) can realize the smooth start of the synchronous motor, reduce the starting current and weaken the disturbance to the power grid. At present, SFC is the main starting mode of pumped storage unit. SFC can produce frequency variable AC power to start the pumped storage unit, with soft starting function. This paper introduces in detail the control structure of the static frequency converter (SFC) valve group of pumped storage unit and the key technology of control and protection of thyristors. It has solved the technical problems such as wide bandwidth pressure energy extraction and instantaneous protection of thyristor in the valve control unit, and has been applied in many pumped storage units.

As global concern for environmental issues continues to grow, reducing carbon emissions has become one of the key tasks across various industries. The steel industry, as one of the major contributors to carbon emissions, holds significant importance in accurately predicting carbon emissions. This paper proposes a carbon emission predicting model based on Stacking framework with Particle Swarm Optimization. To address the issues of missing data and dimensionality in the carbon emission prediction process, the data is preprocessed, and within the Stacking ensemble learning framework, foundational models such as XGBoost, SVR, and KNN are selected as base learners, while Ridge regression is chosen as the meta-learner. The fitness function is defined using the error metric of model outputs, and PSO is utilized to optimize the hyperparameters of the base learners. Finally, the optimized hyperparameters obtained are incorporated into the model to validate the effectiveness of the proposed model through practical examples. The experimental results demonstrate that the optimized Stacking model can further improve prediction accuracy compared to the non-optimized Stacking model.

This article focuses on the theoretical calculation method of low-frequency magnetic shielding of double-layer conducting plates with periodic apertures. The shielding effectiveness is measured when the double-layer CPPA is placed be-tween a pair of conductor rings, one ring for emissing and another ring for receiving. A surface-impedance-based theoretical model is developed to predict the shielding effectives, and the model is simplified under the quasi-static condition. The integral formula works well when the plate-to-plate distance is larger than the aperture diameter. In addition, a physical model was built in the laboratory for measurement, and the theoretical calculation results were compared with the actual measurement results. Finally, an approximate formula is obtained by simplifying the formula under some assumptions and the conclusions of some literatures.

In order to enable effective assessment of the development factors and benefits of various electric energy substitution technologies, and provide clear goals and reasonable development directions for the development of electric energy substitution technologies at the county level, it is necessary to establish a comprehensive, universally applicable, and rational indicator system and method for selecting electric energy substitution technologies. In this paper, a method for electric energy substitution technologies selection based on the cloud theory and the improved technique for order preference by similarity to ideal solution (TOPSIS) method is proposed. Firstly, based on the investigation of the county’s energy consumption market, the selection indicators for electric energy substitution technologies are constructed. Secondly, considering the fuzziness of different indicator weights in the process of selecting electric energy substitution technologies, the reverse cloud combination weight method is proposed to achieve the fuzzy dynamic description of indicator weights. Finally, based on the TOPSIS model and cloud model calculations, a comprehensive cloud model of weighting for electric energy substitution technologies is obtained, and the cloud distance is used to replace the traditional Euclidean distance, thereby achieving the comparison and selection of electric energy substitution technologies. The results of the case study verify the effectiveness of the proposed method.

The permanent magnet-assisted synchronous reluctance motor combines the advantages of the permanent magnet-synchronous application prospects of motors. This article designs a double-rotor permanent magnet reluctance motor, and the two-dimensional finite element model of the motor is established by using the RMxprt module. Conduct sensitivity analysis on the key parameters affecting the torque of synchronous reluctance motors, determine the optimization variables, stratify the variables, establish the kriging response surface model of the average torque and torque ripple, and use the genetic evolution optimization algorithm to obtain the optimal solution set. Finally, the feasibility of the optimization method is verified by simulation, and the results show that the performance of the optimized motor has been improved and the optimization goal has been achieved.

Optical magnetic field sensors have the advantages of small size, light weight, good insulation properties, and high stability. They have a wide range of applications in the field of magnetic field detection, especially in the internal magnetic field detection of transformers. During long-term operation, the temperature inside the transformer will rise, causing drift in the static operating point, which affects the measurement accuracy. In order to study the interference of temperature changes on magnetic field measurement, this paper analyzes the mechanism of temperature affecting the static operating point and the optical rotation coefficient based on the model of light reflection and refraction in crystals established by the team. Finally, a method using a broad-spectrum light source to suppress interference caused by temperature fluctuations is proposed.

For the power quality problems caused by the large-scale access of distributed renewable energy to the distribution network, considering the fluctuation and uncertainty of distributed generator (DG) output and the characteristics of different response time scales of different load types, a method using optimal dispatch model for active distribution network (ADN) with demand-side response on day-ahead-intraday scale. Firstly, the loads are classified and the curtailable and shifting loads are modeled and analyzed from the perspective of user side and distribution network side simultaneously. Secondly, a day-ahead-intraday optimal dispatch framework based on MPC (Model Prediction Control) is proposed, and the role and relevance of the day-ahead and intraday parts are explained respectively. Then it analyzes the day-ahead and intraday goals and constraints respectively and elaborates its control process. Finally, the improved IEEE-33 node model is used to verify and analyze the model, and it is verified that the proposed model can precisely analyze and effectively optimize the power quality of the distribution network and improve the economy of the grid side.

The fault monitoring of transformers is critical for the operation of power systems. However, the traditional wireless sensor networks (WSNs) node has a short battery life, making it difficult to maintain the power supply in harsh environments such as strong electromagnetic fields and vibration noise in transformers. A MEMS AlN piezoelectric beam was designed to harvest the vibration energy at the transformer vibration frequency of 50 Hz. The resonance frequency of vibration harvester system is usually higher than 50 Hz. To reduce the resonance frequency of the MEMS harvester, a folded beam was designed and optimized using the finite element method and theoretical calculation. The results of the two methods are basically consistent. The resonance frequency, output voltage and power were analyzed, and the results show that the structure can effectively reduce the resonance frequency to 50 Hz.

The reliability of substation equipment is the foundation for the safe operation of the power grid. Wireless sensor networks play a crucial role in the perception, transmission, and processing of operational data, providing important support for the maintenance and operation control of power grid equipment. To figure out the coverage problem of wireless sensor networks in substation scenarios, an improved dragonfly algorithm based on chaotic mapping and Cauchy mutation (CCDA) is proposed in this article. The initial velocity of the population is generated by the algorithm using two-dimensional logical chaotic mapping to guarantee population diversity. With a probability decreasing as the number of iterations increases, Cauchy mutation is applied to the current iteration's best individual to escape local optima, enhance the ability to explore the overall situation and improve solution accuracy. The simulation results show that, compared with dragonfly algorithm, sparrow search algorithm and random deployment algorithm, the proposed algorithm can effectively improve the network coverage performance under the premise of high convergence speed and strong global search ability.

With the integration of large-scale new energy into the grid, flexible control equipment is crucial to the quality, safety and stability of grid power supply. This paper firstly introduces the mathematical models of flexible power transformer and United power flow controller (UPFC), and based on the unique background and existing problems of Hebei South Grid, we study the impact of two flexible control devices on the current distribution of Hebei South Grid based on PSD-BPA simulation. The simulation results show that selecting the transformer tap voltage based on the current delivery capacity can effectively solve the problem of heavy and overloaded main transformer of 1000 kV Xiong’an station. At the same time, installing UPFC equipment on the most serious overload lines can improve the heavy and overload situation of 500 kV Langfang area lines. It is concluded that the flexible control equipment can solve the problem of uneven current distribution, exceeding the limit and not meeting the N−1 calibration, and support the safe and stable operation of the power system.

The existence of soft normal open points (SNOP) in flexible interconnected distribution networks makes traditional fault location methods difficult to apply. This article proposes a method for locating fault sections in flexible interconnected distribution networks using waveform similarity of positive sequence current transient components. Firstly, considering the typical topology and control strategy of the system, analyze the fault characteristics of the flexible interconnected distribution network during short circuit faults. On this basis, the transient components of positive sequence current at different positions are extracted, and the waveform similarity is described by calculating cosine similarity. Finally, the Teager energy operator is used to accurately calibrate the fault time, and the intelligent distribution terminal is used to transmit information. By comparing the waveform similarity at different positions, a flexible interconnected distribution network short-circuit fault location criterion is constructed. The feasibility of the proposed method was verified through modeling and simulation, and the effects of fault location, fault type, transition resistance, and sampling frequency on the positioning results were analyzed.

The layout of PCB power devices is a key factor affecting the temperature distribution of power electronics. However, the current targeted optimization methods suffer from large temperature calculation errors and optimization limitations. Therefore, this paper carries out a thermal layout optimization study of PCB power devices based on finite element and genetic algorithm, and verifies it. Firstly, this paper writes a MATLAB finite element program (hereinafter referred to as MFEP) for the initial layout temperature calculation of PCB power devices, and the error is found to be around 0.3% by comparing with the simulation results of ANSYS and the simulation time is reduced by about 71% compared with that of ANSYS. Then the optimization model is established. Finally, This paper uses MFEP and genetic algorithm for PCB power device thermal layout optimization, and ANSYS is used to verify the optimization results, and the maximum junction temperature of the MOSFETs on the PCB after optimization is reduced by about 19 ℃ compared with the initial layout, down to 83.3% of the initial layout.

Currently, the calculation of dead time in a full-bridge Class-D zero-voltage switching (ZVS) converter is mainly based on the snubber capacitance structure connected in parallel with the fixed capacitance switching devices. There are few analyzes for calculating the dead time for Class-D full-bridge converters using the parasitic capacitance of the switching devices as the snubber capacitance. Under high-frequency operating conditions, too short or too long a dead time can cause the Class-D full-bridge converter to lose ZVS, resulting in significant power loss or even damage to the device. Therefore, this paper analyzes the operation of a Class-D full-bridge converter using the parasitic capacitance of the switching devices as the snubber capacitance, and calculates a suitable dead time. Then, a prototype 4 MHz Class-D full-bridge converter based on silicon carbide devices is developed, and the experimental results show that setting the dead time according to the calculation method proposed in this paper ensures the operation of the prototype under ZVS conditions.

To achieve the goals of carbon peaking and carbon neutrality, hydrogen energy has become an important solution for clean energy. In this context, this paper proposes an optimized configuration scheme for hydrogen energy storage in park integrated energy systems, taking into account the medium/ long-term electricity-carbon price. Based on the analysis of the impact of medium/ long-term electricity-carbon prices on the optimization of power flow in the industrial park, a multi-energy coupling model for long-term hydrogen energy storage is established. A monthly scheduling simulation period is adopted to establish an optimized configuration model for hydrogen energy storage in the integrated energy system of the industrial park, considering the time cost of capital and aiming to minimize annual operational costs. The model is solved by a genetic algorithm combined with a mixed integer linear programming algorithm. Case studies analyze the economy of the industrial park after the configuration of hydrogen energy storage and the decision-making of various energy flow scheduling, which verify the economy and feasibility of the proposed model.

Brain waves of different frequencies are generated when the human brain functions, and γ waves are closely associated with higher cognitive functions, such as learning and memory. It has been observed that an electromagnetic field with specific frequency, amplitude, and duty cycle can enhance γ wave oscillation, thereby effectively improving human cognitive function. Building upon this discovery, this paper introduces a wearable pulsed magnetic field generator designed to enhance human cognitive abilities. The device allows for adjustable magnetic induction intensity of the output pulse magnetic field within the range of 0–5 mT, adjustable frequency of the output magnetic field within the range of 0–50 Hz, and adjustable duty cycle of the output magnetic field within the range of 1–50%. Furthermore, the device can generate a 5 Hz pulse wave modulated at 40 Hz (and can also produce a 5 Hz modulation of a 40 Hz pulse wave). The output of the device is both adjustable and stable, making it suitable for conducting experimental studies on cognitive function improvement.

In order to solve the problem of flexibility for large scale renewable energy bases, comparison on the application characteristics, especially water consumption constraints and high altitude capacity discounting is conducted on different flexible power sources. A synergistic optimal model describing renewable energy resource bases combined with flexible power sources and energy storage was established, which considered the characteristics of consumption constraint, capacity constraint, start-stop constraint and ramp-up constraint, etc. The optimization method is validated with the case of integrated energy bases to realize the optimal economic allocation.

In view of the dual-carbon goal proposed by the state, increasing the proportion of green power trading is a key initiative to realize the “dual-carbon” goal, but green power and carbon emissions have not yet been fully coupled, and the way of purchasing green power to offset carbon emissions is too single, so how to scientifically calculate the baseline for offsetting carbon emissions from green power and stimulate the consumption of green power on the user side is a problem that needs to be solved at present. First of all, the study from the carbon emissions accounting and green power emission reduction value measurement of two aspects; Secondly, the high carbon emissions of the industrial sector as an example, the use of cluster analysis to assess the emission reduction potential of a number of industries; then based on this, from the industry of total carbon emissions, carbon emissions intensity and the proportion of electricity consumption of the three aspects, to the exploration of constructing the embodiment of the industry differences in the calculation model of the green power to offset the carbon baseline; Finally, through the analysis of the case to validate the Finally, the viability of the model is verified through an example analysis, and the baseline for the mandatory and key emission reduction categories of industrial industries is calculated.

With the proposal of “carbon peaking and carbon neutrality” target, the proportion of new energy in China’s power generation side is increasing, and it is a general trend for new energy to enter the market and participate in trading. However, there is a big risk for new energy to enter the market, and it is necessary to seek an effective way to avoid the risk and promote the new energy to enter the market, which is a hot and difficult issue in the current research. This paper firstly analyses the risk of high proportion of new energy market transactions; proposes CFDs to help new energy avoid the risk of entering the market, including the multi-factor linkage of government-authorized CFD and the market-based CFD with LMP, and modelled the trading of different types of marketable CFDs; Finally, an example is given to verify the validity of the model and the feasibility of CFDs.

This paper mainly studies the main topology of the active neutral point clamp five-level (5L-ANPC) inverter and analyzes the working principle of the inverter. Because the traditional space vector pulse width modulation (SVPWM) method of the inverter requires the operation of trigonometric function on the time calculation of the sector, which increases the complexity of the inverter control, an improved SVPWM modulation method based on g-h coordinate system is realized. The modulation algorithm uses the feature that the basic vector of three-level inverter is 60°, establishes a 60° vector coordinate system, avoids the complex trigonometric function operation in sector time calculation, greatly reduces the calculation workload required for the implementation of the control algorithm, reduces the difficulty of the implementation of the algorithm, and improves the operation speed of the inverter. By building a software model for simulation and conducting experimental verification on the effectiveness of the algorithm.

Constant current sources are widely used in various fields such as industrial production, aviation, and military applications. The level of ripple in these constant current sources is crucial for ensuring the stability and reliability of equipment and systems. This study focuses on the two-phase interleaved parallel Buck circuit. Based on the analysis of its ripple suppression principle, the circuit parameters were designed and the control strategy was optimized. Finally, the designed two-phase interleaved Buck circuit was validated in Simulink for its effectiveness in suppressing current ripple under conditions of load stability, load fluctuations, power supply fluctuations, as well as simultaneous fluctuations in load and power supply. Simulation results indicate that the two-phase interleaved Buck converter exhibits promising performance: the output current ripple is less than 1% during load stability, less than 1% during a 10% power supply fluctuation, less than 1.5% during a 10% load fluctuation, less than 1% during rapid recovery to stability after load transients, and less than 1% during simultaneous load and power supply fluctuations. Theoretical analysis and simulation validation in this study effectively demonstrate the converter’s ability to suppress current ripple under perturbations within a certain range of both load and power supply.

The transmission chain of wind turbine shaft system exhibits wideband forced torsional vibration in the low-frequency range, which affects the stable operation of the turbine. In this paper, an RBF neural network is incorporated into the forward channel of the model reference adaptive control (MRAC) with input-output, forming the RBF neural network model reference adaptive control (RBFNN-MRAC). The three inputs of RBFNN-MRAC are identified, and the controlled object composite control signal, and adaptive control law are reshaped. This enables adaptive tracking of the gain coefficient, damping ratio, and center frequency of the band-pass filter in active damping control, ensuring that the controlled object tracks the reference model. Simulation results demonstrate that the proposed method effectively suppresses wideband forced torsional vibration, reduces torque fluctuations in the transmission shaft, and achieves smoother and more reliable generator output power.

Regional integrated energy system (RIES) widely involves many types of energy coupling, such as electric energy, thermal energy, cold energy and so on, and faces many challenges in planning. Realizing the coor-dination and complementarity of supply and demand among various energy sources and taking into account the flexibility of demand is a problem that must be considered in the process of integrated energy planning. A regional integrated energy planning method considering demand response is proposed in this paper. First of all, the energy configuration and load demand of four typical application scenarios of integrated energy in in-dustrial park, school, hospital and port area are analyzed, and the equipment configuration scheme of typical scenario is given; secondly, the demand response models of electricity, heating and cooling loads guided by price are established respectively. Finally, based on the energy hub (EH) model, a integrated energy planning model aiming at minimizing the sum of equipment investment, operation cost and demand response com-pensation cost is established, and the linearization method is used to solve the model. Relevant examples show that the proposed method can effectively carry out the integrated energy system planning in typical scenarios and reduce the planning cost.

Demand response is an effective means of shaving peaks and filling valleys. This paper focuses on analyzing the demand response of small and medium-sized users in the case of participating in the electricity market through load aggregators. Firstly, a demand response model is established for load aggregators with small and medium-sized users to participate in the electricity market. Secondly, based on the degree of control that the load aggregator has on user resources, the equipment is divided into partially controlled and fully controlled equipment, and the demand response potential (DRP) forecasting methods are given respectively. Then, an incomplete information static game model of the bidding decision in the upper wholesale market and an optimal bidding model in the lower retail market are constructed. Finally, actual data from a large residential area is employed to illustrate the model and calculate the bidding results.

Aiming at the problem of intermittent and fluctuating wind power generation that leads to the difficulty of real-time power balancing in system operation, this paper proposes a power system operation optimization strategy compatible with Battery Energy Storage System (BESS) and Demand Response (DR). Firstly, a power system framework for a high percentage of wind power access is proposed, and the imbalance problem between the supply and demand sides is reviewed. Secondly, the basic principles of BESS and DR models with their operational constraints are introduced. And then, typical scenarios are selected based on the real-time data from the supply and demand side using the K-means-DBI-based clustering method. Finally, three operation strategies are designed by the principle of single variables and are applied in different typical scenarios for simulation and analysis. The results show that the proposed strategies can effectively reduce the operation cost of the power system while effectively solving the imbalance problem.

In order to reduce the overall power loss of the bidirectional active bridge (DAB) converter and optimise its dynamic characteristics; this paper proposes a hybrid optimal control strategy based on the output voltage model predictive control of extended phase-shift modulation and gradient descent algorithm. The state space model of the DAB converter is established by analysing its operating modes under extended phase shift; the switching tube and transformer losses of the DAB converter are investigated to obtain the integrated loss model of the DAB converter; and the output voltage model predictive control is combined with the gradient descent algorithm to optimise the target power loss. Simulation results show that compared with the traditional PI control, the transfer efficiency of the method proposed in this paper is improved by about 3.7%; the dynamic recovery time is reduced by about 80% and the output voltage fluctuation is reduced by about 76% when the input voltage and the load are perturbed, which verifies the effectiveness of the control strategy.

This paper focuses on the robustness issue caused by load resistance variations in the dual active bridge DC-DC (DAB) converter. It proposes a robust model predictive control algorithm and establishes an interval dynamic model. The algorithm consists of two parts: offline and online. In the offline part, the system parameters are treated as intervals instead of single values, and the corresponding interval dynamic model is established. Then, linear matrix inequalities (LMI) are used to solve the feedback control gain sequences. In the online part, the actual control law of the system is determined based on the position of the state variables in the polyhedral invariant set. Simulation results demonstrate that the designed controllers can maintain stable voltage output and good dynamic characteristics of the DAB converter under input voltage disturbances and load resistance variations. This ensures a certain level of robustness. Simulation results demonstrate the ability of the designed controllers to maintain stable voltage output and good dynamic characteristics of the DAB converter under input voltage disturbances and load resistance variations, ensuring a certain level of robustness.

FRIB is a new generation radioactive isotope beam facility, which generates intense beams of particles composed of extremely rare nuclei that cannot be found on Earth, for the purpose of studying interactions in nuclear physics and nuclear astrophysics. With the rapid development of high-energy physics in recent years, the requirement that magnets must be made of superconducting materials has led to the demand for higher magnetic fields and greater reliability. The superconductive dipole magnet, as one of the essential components of FRIB, plays a crucial role in deflecting particles.In this work, a superconducting dipole magnet was fabricated and tested for FRIB. The magnet has a beam orbit with a total length of 2260 mm, a height of almost 2200 mm, and a width of 1660 mm, with the volume of the liquid helium vessel about 500 L. The peak field in the beam center under operating current is 2T, and the magnet consists of two low-temperature superconducting (HTS) rectangular coils. Each coil is operated with a current of 200 A. After a series of fabrication processes such as winding, terminal wire, impregnating, welding and assembly, the magnet was ramping up only one time at 4.2K to validate the design.The results of the first test were in excellent agreement with the objectives of the theoretical design, demonstrating the success of the magnet’s fabrication.

One important way to support the double carbon strategy is to develop electric vehicles (EVs). With the rapid growth of EVs, we propose a low-carbon economic and orderly charging strategy for EVs in the residential area based on dynamic charging prices to address the problem of increasing peak-to-valley problems caused by disorderly charging. In the residential area, EVs and distributed power sources are aggregated separately, with the EV aggregator aiming to minimize carbon trading and charging costs contribution title. The distributed power source aggregator aims to minimize operating costs and net load peak-valley difference in the residential area. A master-slave game model for the EV aggregator and distributed resource aggregator is constructed, and the equilibrium solution of the game with dynamic charging prices is obtained by combining genetic algorithm and CPLEX. The simulation result shows that the proposed strategy can generate a reasonable dynamic charging price, which can improve low-carbon and economic benefits of the residential area while consuming distributed power locally and lowering the peak-to-valley difference of residential load.

In order to solve the problem that the integration of Distributed Generation (DG) into the distribution network leads to changes in the grid operation mode and affects the optimal operation of the grid, this paper proposes a reactive power optimization method for distribution network containing distributed power supply based on improved particle swarm optimization. The inertia weights and acceleration factors of the particle swarm optimization are improved for the reactive power optimization problem. An optimization model with the objective of minimizing active network loss is established, with full consideration of the constraints of power balance, control variables and state variables. And the improved IEEE-33 node system is simulated and analyzed, and the validity and practicability of the model are verified by comparing with the traditional particle swarm optimization.

In this paper, a cascading model combining operation dynamics and network structure of modular cyber-physical power system is proposed, and the impact of malware attacks on the cascading failure of modular system is analyzed. First, considering the structural and functional characteristics of the cyber-physical power system, a heterogeneous modular coupled network model is established. Then, the effects of malware spreading in information network and power flow overload in power grid on the cascading failure are analyzed. Finally, the impacts of attack strategies, community structure strength and coupling mode on the cascading failure are investigated. The results indicate that there is an optimal time point for malware to attack the power grid, and the attack strategy based on betweenness distribution of power nodes is more destructive. Furthermore, each initial propagation time of malware corresponds to a specific community structure strength of information network, which makes malware attacks more effective. Moreover, the disassortative coupling mode can improve the robustness of the system against malware attacks.

In the context of achieving carbon peaking and carbon neutrality goals, building sustainable substations throughout their entire life cycle is of paramount importance. To promote the development of green and low-carbon substations, this paper established a comprehensive evaluation index system that spans the planning and design stage, construction stage, and operation and maintenance stage. The Analytic Hierarchy Process (AHP) method is employed to determine the weight of each index, and the fuzzy comprehensive evaluation method is used to assess the green and low-carbon rating of the substation based on the principle of maximum membership degree. To validate the methodology and selected indicators, a 110 kV substation in Fujian province is employed as a case study. The results demonstrate that the project qualifies as a three-star green and low-carbon substation, affirming the reasonability and effectiveness of the chosen evaluation index and the weight assignment method. Consequently, this study provides a valuable theoretical guidance for the evaluation and development of green and low-carbon substations and offers practical references for their construction.

With the rapid growth of global energy demand and the increasingly serious problem of climate change, it is very important to explore sustainable low-carbon transmission technology. Aiming at the development of low-carbon technology in power transmission engineering, this paper introduces the current development of power transmission engineering, and sorts out the low-carbon technology of power transmission engineering from three aspects: design, construction and operation. In the design stage, the influence of transmission line layout optimization on energy saving and emission reduction is mainly discussed. In the construction stage, the energy-saving measures of new towers and grounding electrodes are summarized. In the operation stage, the principle and advantages of transmission wires and fittings are mainly analyzed, and the monitoring system of transmission lines is optimized. Finally, through the analysis of the current development direction of low-carbon technology, the future research of low-carbon technology is prospected.

The goal of “dual carbon” and the goal of building a new power system also put forward new requirements for power transformation engineering. The application of various low-carbon technologies in the whole life cycle of the power transformation engineering and the construction of low-carbon or zero-carbon substation is a research hotspot at present. This paper analyzes the possible low-carbon technology and its carbon reduction benefits from three stages: design and planning, architecture and construction, operation and maintenance. In the design and planning stage, substation location is essential; In the architecture and construction stage, there are low-carbon technologies and energy-saving measures such as prefabricated building and classification and reuse of construction waste; In the operation and maintenance stage, there are various intelligent systems and energy-saving equipment such as the joint inspection system, SF6 gas replacement and low-energy transformer. It is hoped that these low-carbon technologies can provide a reference for future low-carbon power transformation engineering.

Taking the cascaded H-bridge (CHB) inverter as the object of study, the structure of the inverter system is analyzed and the modulation strategy of the system is investigated. A control strategy based on a three-phase cascaded H-bridge topology is proposed for a PV grid-connected inverter system. The scheme adopts a carrier level phase-shift modulation strategy, which can realize the maximum power point tracking of the front-stage PV string, the control of the grid-connected current, and the grid-connection of the inverter . Finally, the inverter with the proposed strategy is simulated in MATLAB/SIMULINK environment, and the simulation results prove the correctness and feasibility of the control strategy.

With the development of science and technology, today’s society has put forward higher requirements for the performance of power supplies in industrial systems such as aerospace, communication systems, mining and machinery. At present, distributed power supply system accounts for a large proportion in the power supply system. Miniaturization, standardization and modularization are the development trend of distributed system power supply. The research content of this paper is a wide-range input quasi-resonant forward and forward DC/DC converter applied to the rear stage of distributed power system. Firstly, a wide range quasi-resonant positive/negative DC/DC circuit topology based on positive/negative circuits is introduced in this paper. Secondly, the operation process of the wide range input quasi-resonant forward/forward converter in CCM mode, CRM mode and DCM mode is analyzed. Finally, according to the characteristics of the converter, the PWM fixed-frequency and Constant Opening Time (COT) hybrid control strategy is designed to control the closed loop of the circuit, which is a hybrid control method that specifies the frequency regulation duty cycle and the constant on-time regulation frequency.

For landscape renewable energy access areas, there is not only a correlation between wind farms and photovoltaic power plants, but also a certain correlation between wind power and photovoltaic power generation. When evaluating the credibility of the comprehensive capacity of landscape renewable energy, the reliability evaluation index selects the unloading rate of the commonly used index, and the credibility of the capacity needs to be estimated. The traditional Monte Carlo simulation method has a long calculation speed. This paper proposes to use the recursive function method to calculate the trusted capacity, further improve the calculation speed of the trusted capacity, and verify the feasibility of the method from two aspects of calculation speed and calculation error. And explore the impact of different scenery ratio and different total installed capacity on the credibility of the comprehensive capacity.

In order to reduce the prediction error of short-term wind power, an EMD-LSTM based short-term wind power combination prediction model is proposed. First, the EMD algorithm is used to decompose the original wind power data into several eigenmode function components and trend components, and then each component is combined with NWP (Numerical weather prediction) wind resource data to establish a long and short term memory network for regression prediction. Finally, the prediction results are compared with the actual wind power to verify the prediction performance of the proposed model. The experimental results can reasonably predict the wind power with high prediction accuracy. At the same time, an error analysis method based on wind power model is proposed. By decoupling method, we find the cause of power prediction error, that is, the error caused by each link. This method can effectively excavate the causes of errors in the prediction model and the proportion of errors in each link, and provide accurate support for further improvement of wind power prediction errors.

With the continuous improvement of voltage levels in the field of current measurement, the requirements for measurement and protection accuracy are also increasing. The traditional current sensor technology has many shortcomings due to its design, such as low precision and easy to be affected by external temperature. The current measurement technology of ring point Hall sensor is a current detection method evolved from the traditional Hall current measurement technology. Hall current sensor is the most commonly used means of current detection in the industrial field. This method is based on the ampere loop theorem, Hall principle and superposition principle for real-time measurement and analysis of a certain range of current. Its advantage is that it can effectively realize the electrical insulation between the measured signal and the measured signal. In this paper, the current measurement technology and its application of a ring point Hall current sensor are studied.

Misalignment between the transmitter and receiver coils, manufacturing tolerance and temperature drift of the compensation capacitors in a wireless power transfer (WPT) system will inevitably affect its performances, such as efficiency, output power, zero voltage switching (ZVS) operation, and voltage and/or current stresses of the power semiconductor devices. The impedance detuning is the essence of the system performance deterioration. Therefore, it is mandatory to detect and regulate the resonant condition of the WPT system in real time. This manuscript provides a current state of art review of all available impedance tuning methods. The variable operation frequency control and resonant frequency regulation of the compensation topology are the two basic solutions. And their working principles and inherent characteristics are analyzed qualitatively and compared. Some topics worthy of research are also suggested to make contribution to the development and commercial applications of the wireless charging technique.

A high step-up dc-dc converter (HSUC) is proposed, which uses a coupled inductor and a boost unit to improve boost capability. The proposed converter has the characteristics of large voltage gain and low voltage stress of semiconductors. Thus, MOSFETs with low rated voltage can be used to reduce conduction loss. Besides, since a boost inductor is placed in the input source, the input current is continuous, which is beneficial for battery and the renewable energy resources. The working principle is illustrated in detail. Comparison among different HSUCs is discussed in detail. Finally, a simulation model is built in PSIM. Simulation results confirm the theoretical analysis.

Realizing the real-time monitoring of carbon emissions from coal-fired power plants is of great significance to achieve the double carbon target. At present, the carbon emission monitoring system of coal-fired power plants in China has a serious lag in timeliness, low data collection efficiency, and is not conducive to data mining and management. In this paper, we design a real-time carbon emission monitoring system to address the above problems, integrating the material conservation method and emission factor method to establish a real-time carbon emission calculation model. In this paper, we tested a supercritical unit of a power plant in Jiangxi Province, and the test results show that the system can account for the carbon emission of coal-fired power plants in real time, visualize and monitor the carbon emission data of coal-fired power plants in Jiangxi Province in real time, display the data in a more intuitive and easy to understand way, and improve the efficiency of collecting carbon emission data of coal-fired power plants. It provides powerful data support for coal-fired power plants’ carbon emission accounting and assessment as well as carbon trading economics research.

The balance of sub-module capacitor voltage is the necessary guarantee for the normal operation of modular multilevel converter (MMC). With the nearest level modulation (NLM), an improved group-sort algorithm is proposed in this paper. Based on the average value of arm sub-module capacitor voltages, the sub-modules are divided into two groups, the higher value group and the lower value group. According to the direction of arm current and the number of on-state sub-modules given by NLM, partial sorting in one group is enough to decide the states of the sub-modules in the next cycle, time complexity of group-sort algorithm is reduced obviously and the same equalization effect is achieved. Finally, simulation is carried out based on a 23-level MMC on MATLAB/SIMULINK. The efficiency and correctness of the group-sort algorithm are proved.

In order to solve the problem of carbon emissions in substations, a substation-microgrids system with microgrids as the source side and substations as the load side is proposed. Firstly, a mathematical model of the proposed substation-microgrids system is established, with wind and photovoltaic power generation in the microgrids as the main power supply of the system. Then, the electric energy storage in traditional uninterruptible power supply (UPS) system is replaced by a hydrogen energy storage system, and electric vehicles (EV) is introduced for orderly charging. Finally, in order to verify the effectiveness of the proposed substation-microgrids system, a multi scenario comparative analysis is conducted based on the Cplex solver. The simulation results show that the proposed model not only effectively reduces carbon emissions, but also achieves energy cascade utilization and reduces the system's wind power and photovoltaic power curtailment rate.

To address the impact of high-power pulse loads on the gas turbine and power system in marine gas turbine power generation system, this paper proposes a coordinated control method of engine-load-storage. The control method can actively exert the regulating ability of the micro gas turbine under pulse load, optimize the power borne by the energy storage, and realize the stable operation of the gas turbine and power grid. The energy management system employs a dual-filter approach to decompose the load power, assigning the decomposed power components of different frequencies to the flywheel energy storage, battery, and gas turbine generator unit accordingly. The separate control strategies of gas turbine, power grid, and energy storage systems are further coordinated to achieve overall coordinated control and optimized operation. Further, the synergistic interactions among subsystem control strategies of the engine, grid, and energy storage ensure overall coordinated control and optimized performance. A comprehensive model of a ship gas turbine microgrid system is established based on a 100 kW practical micro gas turbine. The simulation studies demonstrate that the proposed coordination control method achieves coordinated operation among the gas turbine generation unit, load, and energy storage system in the marine gas turbine microgrid. Under the condition of a daily load equivalent to 10% of the rated power of the power generation gas turbine, when a pulse load with a peak power of 70% of the rated power of the gas turbine is connected, the maximum fluctuation of DC bus voltage is 2%, and maximum fluctuation of the gas turbine speed is 0.02%, indicating excellent stability performance.

During GIS (Gas Insulated Substation) operation, Very Fast Transient Overvoltages (VFTOs) are generated, resulting in transient currents flowing through the pipeline that connects the GIS station and the ground network. The impedance of the pipeline reflects the transmission characteristics of electrical signals within the pipeline system. By calculating the impedance of the pipeline, we can obtain information about the transmission mode, transmission rate, and signal amplitude of electrical signals in the pipeline system. This allows us to evaluate the impact of VFTOs on the GIS system. In this paper, a method is proposed to calculate the impedance of horizontal pipelines in GIS stations, taking into account the magnetization curves. The magnetization curves of the pipeline material are measured and used to calculate the magnetizing current in the pipeline during VFTO events. Finite element analysis is performed to calculate the impedance of the pipeline, and the results are compared with those obtained from the traditional approach. The proposed method provides a more accurate assessment of the impact of VFTOs on GIS systems.

Aiming at the wearing adaptability and comfort of energy harvesters, an energy harvesting device based on magnetic springs and friction power generation is designed to collect human movement energy. The effects of magnetic energy product, magnetization direction and winding height of permanent magnets on the performance of magnetic spring power generation were studied, the influence of friction position on friction power generation was studied, an energy management circuit was designed, and a wearable composite power supply system was made, which improved the adaptability of magnetic springs and friction power generation in the wearable field, and provided a reference for the application of energy harvesting technology in the wearable field.

The conduction current of power semiconductor devices serves as a necessary reference value for switching trajectory optimization, junction temperature monitoring, and aging assessment functions of intelligent active gate drives. This paper proposes a detection method for conduction current during switching transient of SiC MOSFET based on second-order passive filtering. Under the high-speed variation of drain current during the switching transient, the mutual inductance coil generates an induced potential. The induced voltage can be effectively restored, and the high-frequency oscillation be attenuated by implementing a second-order passive R-C filter. By selecting specific parameters for resistance and capacitance, the analysis of a second-order low-pass filter function validates the feasibility of using filtering time as an equivalent electrical parameter for the conduction current. The effectiveness of a passive filter circuit is validated through double-pulse experiments. The results indicate that the filtering time demonstrates high sensitivity and accuracy to the conduction current during switching transient. Moreover, the filtering time remains unaffected by the rate of drain current, indicating its strong universality and applicability to different specifications of SiC MOSFET modules.

To solve the VFTO in GIS, it is necessary to perform the earth and GIS interconnection system, and then calculate the impedance to earth. The GIS interconnection system is rarely considered in current studies. To solve the problem of large computation time and meshes, a semi-analytical method is used to decompose the region into two sub-regions and calculate the sub-regions by finite element method and analytical solution method respectively, while introducing tensor calculation in the finite element part greatly reduces the computation time. The results are calculated in case of single-phase and three-phase, meanwhile, the frequency domain results for the overall system were analyzed. The approach proposed in this paper can be used to solve the problem of GIS impedance to ground, and has a large improvement in computational performance.

Targeting the issue that the battery pack life is shortened due to the inconsistent capacity and voltage between single cells in the train battery pack, which may even directly affect the normal use of the electronic equipment inside the train or lead to difficulty in starting some fuel trains, an offline battery pack balancing maintenance equipment method based on the isolated DC-DC converter is designed. In this device, the open circuit voltage (OCV) of the single cell in the battery pack is adopted as the input variable of the balancing control, and the balancing takes the constant voltage current limiting mode. The current is automatically adjusted in real time according to the set voltage and the actual dropout voltage of the battery. The method of combining the DC-DC converter with the electronic switch array is used to realize the energy transfer between single cells. The balancing test data indicates that the device can control the balancing dropout voltage within 10 mV, and the balancing current can be as high as 10 A, which improves the balancing efficiency and effectively reduces the inconsistency between single cells.

Currently, the selection of submarine cables is primarily based on steady-state ampacity. However, in practical situations, submarine cables are not always operating at full load, resulting in a difference between the steady-state ampacity and the actual maximum current that the cable can withstand. In this paper, based on the IEC-60853 standard, the periodic load corresponding to the submarine cable’s cyclic ampacity is studied. A computational model is developed to calculate the cyclic ampacity of the submarine cable under typical cyclic load curves. The COMSOL finite element analysis software is used to establish a multi-physics simulation model for high voltage AC submarine cables under different installation methods, including burial and laying. The influence of environmental factors on the cyclic ampacity of the submarine cable under these two typical installation methods is investigated. The results show that under the burial installation method, as the seabed depth increases and the soil depth decreases, the cyclic ampacity of the cable increases. Under the laying installation method, as the seabed depth increases, the cyclic ampacity of the cable also increases. Furthermore, both the steady-state ampacity and the cyclic ampacity of the cable under the laying installation method are higher than those under the burial installation method. The findings of this study can serve as a reference for selecting the installation method and cable type for submarine cables.

With the increasing integration of wind and solar power generation into the power grid, virtual synchronous generator (VSG) has become a primary research object. Combining the inverter control strategy to compensate for the performance of synchronous generators, also can provide voltage support and inertial support characteristics. This paper presented the topology and mathematical modeling of the VSG and detailed operating strategies for P/F and Q/U have been established. Then a simulation model is developed on MATLAB platform to study the transient synchronization characteristics of the VSG. The anti-interference, robustness and grid distortion rate of the VSG under the different cases are researched. By adjusting control parameter variables, the impact of inertia damping on system output power is analyzed. This technology reduces the difficulty of grid connection and the harmonic distortion rate, improving dynamic stability and overshoot. Besides, this technology also provides the inertia and damping of synchronous generators, improving the anti-interference and robustness for the power grid.

To meet the rapid development of distributed photovoltaics and enhance the grid’s ability to accommodate distributed photovoltaics, it is necessary to fully leverage the power supply role of distributed photovoltaics. This will accelerate the construction of a new type of power system and energy system with gradually increasing penetration of renewable energy sources. Therefore, it is critically important to scientifically and reasonably evaluate the carrying capacity of the distribution grid for distributed photovoltaics and propose improvement measures for the existing shortcomings. This article summarizes the research and current status of the analysis and improvement measures for the hosting capacity of distributed photovoltaics in distribution grids. Firstly, it summarizes relevant domestic and international literature, and summarizes the calculation methods and corresponding shortcomings of the distributed photovoltaics hosting capacity, including power flow back feeding, thermal stability, short-circuit current, voltage deviation, harmonics, and three-phase imbalance. Secondly, it introduces strategies and technologies for enhancing the hosting capacity of distribution grids from the perspectives of generation, network, load, and storage. Finally, it summarizes the shortcomings of existing research and proposes future research directions and challenges.

To study the erosion process in solid armatures during the electromagnetic (EM) launching, this paper constructs the physical model for the launching process and performs three-dimensional simulations. In the model, the Joule heating effect is taken as the volume heat source, while the heating effect due to the contact resistance and friction is considered as the thermal boundary condition on the contact interface between the rail and the armature. The contact problem between rail and armature is resolved at first to obtain a deformed rail-armature structure with a reasonable contact region under the effect of geometric interference and electromagnetic force. Based on this deformed structure, the simulation of the armature erosion is performed. It is found that the erosion in armature initiates from the sides of the leading edge of the contact region, and proceeds towards the center and the trailing edge. The armature erosion obtained by the simulation has similar distribution features to experimental results. The three-dimensional simulation study on the armature erosion conducted in this paper is hence validated.

Electric-field coupled bidirectional wireless power transfer system is suitable for grid, electric vehicles or battery storage devices, enabling energy interaction between them. In the practical application of EC-BWPT technology, the transmission performance of the system is largely affected by the coupling capacitance, and the misalignment of the coupling plate are unavoidable. This paper proposes a dual phase-shifting control method to achieve system tuning by adjusting the relative phase angle under variation of the coupling capacitance. Then, the desired power is obtained by adjusting the internal phase angle of the receiver converter. The coupling tuning and power flow regulation strategy based on phase-shifting control achieves modulation of power flow. Finally, the effectiveness of the proposed coupling tuning and power flow phase-shifting control strategy was verified by simulation.

Aiming at the single-phase full-bridge active neutral-point clamped (ANPC) converter, the traditional space vector modulation (SVPWM) method has the problem of unbalanced loss of internal and external switching devices. Based on the analysis of the switching process, a loss model is established, and a loss-balanced space vector modulation is proposed. When the output voltage of the bridge leg is clamped to the neutral point, the chosen switching states are used to synthesise the reference space vector, therefore the current is freewheeled through the dual commutation loops, thus effectively making the switching loss between the inner switching devices more balanced. Compared with the traditional modulation method, the proposed method can balance the loss while taking into account its operating efficiency, and fully exploit the advantages of the ANPC converter. Finally, simulation and experiment results show that the method is simple to implement, and can effectively balance the loss of switching devices.

The DWPT system with single-phase bipolar narrow-rail has the advantages of high-power density and large lateral misalignment tolerance. However, this structure has significant power fluctuations and power zero points. This article pro-poses a biphase narrow rail that has two windings excitated by two currents with a difference of 90° as a transmitter that can achieve uniform power output in the DWPT system. Besides, the copper and core losses of biphase rails are significantly lower than the values of single-phase rails when the output power is equal.

Aiming at the problems of unstable output voltage and large current harmonic distortion rate of photovoltaic grid-connected, based on three-level H-bridge cascaded inverter, this paper focuses on the topology and control strategy of two-cell cascaded structure. In the system, each photovoltaic module is independently controlled by maximum power point tracking (MPPT), which can improve the power generation efficiency of the photovoltaic system. According to the topological structure and working principle of the three-level cascaded H-bridge inverter (CHI), based on the carrier phase shift control method (PS-PWM), a double closed-loop control method is proposed of voltage outer loop PI control and current inner loop proportional-resonant (PR) control, and its mathematical model and circuit model of photovoltaic inverter is established. The system simulation is carried out in MATLAB/ Simulink. The simulation results show that the system control method can accelerate the current dynamic adjustment speed, reduce the current harmonic distortion rate, and thus verify the feasibility and practicability of the strategy proposed in this paper.

Biological weak magnetic field detection has gradually become a research hotspot.The miniaturized and high performance magnetic sensor detection system has important application prospects in biomolecular detection, magnetic anomaly detection, aerospace and other fields. Traditional biomolecular detection methods are expensive, time-consuming and low accuracy, and are gradually replaced by new magnetic sensor detection methods. In this study, a biodetection system based on the tunnel magnetoresistive effect sensor is proposed to detect magnetosomes in the following magnetotactic bacteria. The biological detection system is composed of the TMR and the differential amplifier, which is of great significance for the early detection of human cancer in the future. In this paper, a biological detection system is first used to simulate the detection of weak biological magnetic field in energized solenoid. The measurement range of the biological weak magnetic field detection system is ± 30 Oe, and the magnetic induction intensity change of 10nT can be accurately identified. The linear regression equation Y = 0.90926 + 0.00113X (R = 0.99983, P < 0.0001, N = 10) was obtained by amplifying the TMR output signal through a differential amplifier. At the same time, the average number of magnetosomes in magnetotactic bacteria is 22.8, which can satisfy the accurate detection of 103 units of magnetotactic bacteria. By measuring magnetotactic bacteria with different gradient concentrations, the regression equation between magnetotactic bacteria concentration and output voltage is Y = 0.90926 + 0.06732X (R = 0.99838, P < 0.0001, N = 6). This method can detect the biological weak magnetic field quickly and accurately with good recovery and reproducibility.

Most of the existing load forecasting methods are based on a single time scale for analysis and research, while the load power sequence has an apparent weekly cycle, daily cycle and seasonal time sequence characteristics. Therefore, this paper proposes an MTSC-GRU load forecasting model that considers the periodic characteristics of multiple time scales. First, the load sequence is divided into three different time scales, 15 min, daily and weekly, based on the temporal characteristics. Second, a convolutional neural network extracts temporal features from the sequences at three-time scales. Then a recurrent neural network is used to capture the long-term temporal dependencies in the load sequences, to learn the internal law of change of the loads, and to introduce the Dropout mechanism to avoid overfitting the model. Finally, the output side fuses and maps the GRU outputs at the three-time scales to realize the short-term day-ahead load timing prediction.

Perovskite solar cells (PSCs) have attracted intensive attention because of high energy conversion efficiency, low-cost materials constituents, and simple solution fabrication process, which are considered as a disruptive technology. Currently, perovskite solar cells have achieved an impressive certification efficiency of 26%. However, the commercialization of PSCs requires addressing two crucial concerns: stability and the remaining challenges associated with scaling up their manufacturing processes. In this paper, we briefly describe the working principle and device structure of PSCs, review recent progress of PSCs in improving photoelectric conversion efficiency and stability, and put forward the remaining challenges along the pathway to their commercialization. Finally, the application prospect of PSCs in power system is prospected.

With the increasing demand for energy, the ultra high voltage direct current (UHVDC) transmission system has received extensive attention. Line commutated converter (LCC) is the most commonly used converter technology in HVDC system. The analysis of its fault characteristics is very significant for the system. In this article, the system structure and basic principle of LCC UHVDC transmission are described, and the situations of normal operation and fault are analyzed theoretically. Based on the actual engineering parameters of the project, the simulation model of ±800 kV UHVDC transmission system is built by using electromagnetic transient simulation software PSCAD/EMTDC. And the fault characteristics are simulated to validate the accuracy of the theoretical analysis.

Eddy current fields are usually used to describe the electromagnetic phenomena in fast-response devices, but this numerical simplification has errors in explaining the current establishment mechanism of conductors. This paper uses the full-wave Maxwell equations and takes an axisymmetric power source-coaxial line-axisymmetric load loop as a typical example to clarify the current establishment mechanism in the conductor under sudden voltage excitation. The field in the air is not established instantaneously, but is sent from the power source to the load in the form of electromagnetic waves along the waveguide. If the characteristic impedance of the waveguide does not match the load resistance, the wave will refract and reflect repeatedly, progressively delivering energy into the load. And the load voltage and current rise in steps, and the rise time is related to the matching degree of the waveguide and the load. Then the solution of the full-wave equation is compared with transmission line theory. The transmission line theory is a circuit simplification from the full-wave equations, but cannot take into account the dynamic circuit parameters of the waveguide and load, which can cause distortion of the solution.

With the continuous development of electronic devices and increasing performance requirements, thermal resistance, as one of the important parameters for evaluating the performance and thermal management effectiveness of heat dissipation devices, is crucial for device performance and reliability. For the thermal resistance measurement of single-sided heat dissipation devices, there are mature calculation and measurement methods available. However, for double-sided heat dissipation devices, the existing measurement methods suffer from significant measurement errors and limitations due to structural asymmetry and dual-sided heat flow paths. In this paper, focusing on rigid press-pack IGBTs, the applicability, error sources, and limitations of commonly used theoretical calculation methods, finite element simulation methods, and experimental measurement methods in double-sided thermal resistance measurement are discussed. By comparing the advantages, disadvantages, and applicable ranges of different methods, this study provides references and guidance for double-sided thermal resistance measurement.

In recent years, Rydberg atoms have been widely employed for electric field quantum measurements. The fundamental principle behind these measurements is the utilization of the double-photon three-level structure to achieve Electromagnetically Induced Transparency (EIT). When cesium atoms are employed as the sensor, the detection light needs to be locked at 852 nm to excite the cesium atoms from the ground state 6S1/2 to the intermediate state 6P3/2. Frequency locking is achieved through the saturated absorption spectroscopy method. Due to the fine energy level structure of the cesium atom's D2 line, the saturated absorption spectrum exhibits six spectral peaks, providing the flexibility to select any one of them as a reference for frequency locking. In this paper, we present an experimental setup where we compare the EIT effects resulting from frequency locking to five different spectral peaks and discuss the influencing factors and optimal selection.

This paper presents a measurement technique for low-frequency electric fields based on the Rydberg atoms. It utilizes the principle of the Stark effect, where non-resonant external electric fields cause the splitting of atomic energy levels, leading to spectral peak frequency shifts. In the measurement system, the photoelectrically converted signal is typically directly connected to an oscilloscope to display the corresponding spectrogram. Therefore, calibration of the laser spectral frequency variations is necessary to convert the time axis of the oscilloscope into a frequency axis. This paper proposes a calibration method that utilizes the existence of two optical peaks, corresponding to the nD3/2 and nD5/2 states of cesium (Cs) atoms, in the absence of an electric field. The theoretical calculation of the frequency difference between these two peaks provides an internal frequency scale without the need for external devices. By applying this calibration method, the time shift of the two peaks measured on the oscilloscope is converted into a frequency shift, allowing the determination of the applied field strength based on the mathematical relationship between the frequency shift and the applied electric field. The principles of the technique are described, and experimental validation is performed.