The Proceedings of the 19th Annual Conference of China Electrotechnical Society

Accurate and efficient liquid distribution control and measurement is very important in many application fields such as energy and power, chemical and pharmaceutical, food processing and laboratory. In this study, the virtual scale technology, which was originally used for solid materials, was extended to liquid distribution system through innovative improvement. This paper discusses the applicability and challenges of virtual scale technology in liquid system, and puts forward innovative improvement measures, including adaptive process design, sensor accuracy improvement, information synchronization enhancement and signal processing algorithm optimization. These improvements enable the accurate measurement of multiple feeding points through a set of metering devices at the total feeding port without additional physical metering devices. The improved virtual scale technology not only improves the accuracy and efficiency of measurement, but also reduces the equipment investment and enhances the automation and information level of the system. The purpose of this study is to provide a valuable reference and reference for the field of liquid dispensing and metering.

Extensive research has investigated the enhancement of boiling heat transfer through electric fields, primarily focusing on the effects of direct current (DC) electric fields. This study seeks to deepen the understanding of the mechanisms involved in boiling heat transfer enhancement when using alternating current (AC) electric fields. By examining the deformation of bubbles in uniform electric fields and the electric potential distribution at the bubble edges, we assess the impact of electric field strength and frequency on boiling heat transfer. The variation in density and dielectric constants between the gaseous and liquid phases results in a polarization charge density at the bubble boundary, causing the bubbles to elongate in the direction of the electric field. Our findings reveal that the electric field not only induces significant bubble deformation but also facilitates bubble detachment, thereby enhancing heat transfer. Specifically, the electric field influences the diameter of detached bubbles, leading to a reduction in size and an increase in detachment frequency, which collectively contribute to improved boiling heat transfer.

When the phase shift Angle of DAB changes, transient DC bias current will appear. In this paper, a transient DC bias current suppression strategy is proposed to achieve fast stability of DAB. The primary H-bridge voltage symmetry line is selected as the current starting point, and its steady-state current value is only related to the outward shift Angle. In this paper, an improved current stress minimization modulation strategy is proposed to realize the fast steady-state transition of the current waveform. At the same time, the transient current increment is controlled, and the transient current stress is effectively reduced. Finally, the effectiveness of the proposed improved current stress minimization strategy is verified by simulation.

With the rapid development of deep offshore wind power, flexible direct current (DC) transmission has become the preferred technology option for grid connection. However, large-scale flexible DC systems present complex control and protection hierarchies and multidimensional strategies, Make a huge Challenges to the safe and stable operation and performance testing of control system hardware and software, as well as performance testing. This paper focuses on the KMVA-level offshore wind flexible DC integration project by the China Electric Power Research Institute. A real-time simulation model for electromagnetic transients and a hardware-in-the-loop testing platform were developed using a CPU+FPGA Heterogeneous computing platform with RTLAB and Hypersim. The platform enables system control testing through full-scale hardware control and real-time digital models. Experimental results show the control system's excellent performance, supporting future offshore flexible DC engineering applications.

Epoxy resin is widely used in the packaging insulation for high-voltage electrical equipment and integrated electronic devices. Its post curing effect during long-term storage may affect the material performance and storage reliability of epoxy packaging products. In this work, the curing temperature of epoxy resin was further enhanced based on the conventional curing process, which is used to simulate the post curing reaction during storage, and its effect on the properties was studied. The results show that, the post curing does not significantly change the molecular structure of epoxy resin, but has a modest effect on the thermal, mechanical and electrical properties, such as the enhancement of glass transition temperature, the increase of storage modulus (in glassy state) and loss modulus, the slight decrease of relative permittivity and dielectric loss, and the improvement of pulsed breakdown field. This work could support the storage reliability assessment of epoxy packaging products.

Self-circulating evaporative cooling technology makes use of the latent heat of working medium phase change to meet high heat flux requirement during the operation of flexible HVDC converter valve. In this paper, a one-dimensional simulation model is established to solve the problem of multi-branch parallel heat source with strong non-uniform heat flux, and a multi-branch self-circulating evaporative cooling experimental system is designed. The accuracy of this model is verified to be better than 9.3%. The model analysis shows that under non-uniform heat flux, the temperature distribution equilibrium is 4.78 in inverter condition and 3.52 in rectifier condition. With the increase of operating pressure, the equilibrium of temperature distribution on the outer wall of the liquid tank is improved. Considering the complexity and cost of this cooling system, single condenser is recommend as the system configuration.

DC side voltage regulation control is one of the key technologies for the stable operation of shunt active power filters (SAPF). A DC side voltage composite control strategy based on improved fuzzy PI control combined with Fast Delay Signal Cancellation (FDSC) filtering is proposed to address the shortcomings of large system overshoot and poor SAPF compensation effect under unbalanced load conditions when using traditional Proportional Integral (PI) control for SAPF DC side voltage stabilization. Firstly, the topology and control principle of SAPF were introduced, and the reasons for asymmetric current distortion in the power grid under unbalanced load conditions were analyzed; Secondly, a fuzzy PI controller was established to combine fuzzy PI control with traditional PI control for segmented control, balancing the dynamic response and steady-state accuracy of the system. To improve the compensation effect of SAPF under unbalanced load conditions, it is proposed to use FDSC to filter out the sixth and second harmonics of DC side voltage under three-phase load unbalanced conditions; Finally, theoretical analysis and simulation results verify the progressiveness of the proposed SAPF DC side composite voltage stabilizing control.

The advantages and disadvantages of electromagnetic railguns with rectangular, arc and round bores are compared and analyzed. It is found that the round bore is consistent with that of conventional guns and it is of better inheritance in engineering application. A 30 mm small bore electromagnetic railgun is designed, with simulation test carried out for lumped power parameters, armature deflection force, structure and temperature rise. Current climbing tests are carried out on thin-arm and thick-arm armatures. The thin tail armature presents obvious burning loss at a current amplitude of 265 kA, while the thick tail armature presents obvious burning loss at a current amplitude of 350 kA, indicating that it can withstand 30 stable fires. The maximum line current density achieved by the small-caliber round-bore electromagnetic railgun is 17.5 kA/mm. The firing test at 450 kA will be carried out later. This study can be used as reference to some extent for the application of small-caliber round-bore electromagnetic railgun.

Cable joint is a weak link with complex electromagnetic backgrounds in power cable line. The electro-thermal distributions of such cable joint are crucial in determining the rated current of the HV power cable, particularly in the limited underground utility tunnel scenarios. This paper establishes an electromagnetic-thermal interacted numerical modelling of 220 kV three-phase HV cable intermediate joints in triangular arrangement, with the multi-physical fields of each cable joint been calculated and compered. Simulation results show that for the cable joints in triangular arrangement, the temperature of the one phase in top side is higher than the other two phases of about 15%, and the electric field intensity is higher than the other two phases of about 30%. The way the cables are laid in the tunnel may be the key cause of these differences. The research in this paper can be consultation for the optimization of cable laying in cable tunnels and maximizing of rated current.

Electric field tomography imaging technique has great application potential in human physiological and pathological detection due to its advantages of non-contact, non-destructive, and functional imaging. However, the existing technique has not been applied in practice due to the high requirements for high-frequency excitation and synchronous phase shift detection. In this paper, we design a high-frequency excitation system for electric field tomography imaging based on FPGA and DDS technology, use fast Fourier method with multi-channel acquisition to realize synchronous measurement of phase shift of same-frequency sinusoidal signals, and develop image reconstruction algorithm based on Tikhonov regularization method. We build an electric field tomography imaging system and conduct experiments to detect target objects with different sizes, positions and numbers using the system. The experimental results show that the system can detect the target objects, verifying the effectiveness and correctness of our work.

Cable crosslinked polyethylene (XLPE) insulation will accumulate space charge under high voltage DC condition, which will cause the electric field distribution to deviate from the expected value and even cause insulation breakdown. The spatial charge distribution contains information and characteristics about charge transport in the insulation, while the leakage current contains information about charge injection and extraction behavior occurring across the electrode/dielectric interface. In this paper, the correlation properties of the space charge and current of XLPE material with the aging state of the insulation is obtained by simultaneously measuring those on the insulated sections of aged and unaged DC cables. The results indicate that as the aging time prolongs, the amount of space charge accumulated during the polarization process first increases and then decreases, revealing different characteristics of charge injection and migration in the aged samples at different stages. The current in the aged cable insulation samples increases, with a more pronounced trend observed in the middle and later stages of aging. During the middle and later stages of aging, a phenomenon of current resurgence emerges in the samples, accompanied by more intense charge injection and migration. Although there are discrepancies in the carrier mobility calculated using different methods, they all exhibit a trend of first decreasing and then increasing.

As a key component of the flexible DC converter valve, DC support capacitor is very important for the stable operation of the whole flexible DC transmission system. Based on the theoretical analysis of the on-line monitoring methods for the capacitance, equivalent resistance and loss of DC supported capacitors, this paper proposes an on-line monitoring method for the capacitance of DC supported capacitors using the existing electrical monitoring of the bridge arm current, submodule voltage and switching state. This method does not need to change the existing valve control system hardware and communication architecture, and adds the capacity data analysis software and online capacity monitoring software on the basis of the original monitoring system to realize the real-time calculation of capacitor capacity and health status analysis. At present, the online capacity monitoring platform has been deployed and applied in the flexible converter station of Fukang Station in Zhangbei. Further analysis of capacitor short circuit or open circuit, excessive internal pressure, capacity attenuation and other fault conditions, proposed early warning, attempt to continue operation, attenuation reassessment, one pole warning, failure protection bypass and other multi-stage fault warning and failure protection protection strategies, effectively improve the operation reliability and safety of the converter valve. This paper provides a comprehensive technical scheme for the on-line monitoring and fault protection of the flexible DC converter valve DC support capacitor, and provides important guarantee for the safe and reliable operation of the core equipment of the HVDC transmission project.

UHF partial discharge detection through UAV is a new method for substation equipment inspection. By obtaining internal discharge signals of equipment through close to live parts, the effectiveness of defect diagnosis can be improved, solving the problems of “large signal attenuation and blind spots” in conventional detection. Due to the influence of small distance of substation equipment, it is necessary to miniaturize the UAV equipped with UHV partial discharge detection device. In this article, three aspects are improved: small sensors, expansion interfaces, and data processing. By combining laboratory and on-site testing, PRPD-PRPS spectra of three types of discharges, including suspended, tip, and surface discharge, were obtained. The relationship between discharge signals and distance was studied, and the device was verified to have good sensitivity, reliability and convenient operation in substation. This device can provide a reference for the UHF detection method through UAV and expand the intelligent inspection method for partial discharge of power equipment.

The preparation of graphene and copper composite line and the application technology of power transformer are the research hotspots for power equipment. As an ideal reinforced phase composite material, graphene has unique two-dimensional structure, high strength, high electrical conductivity and high thermal conductivity and other super mechanical and functional properties. The combination of graphene and high-purity metal copper greatly improves the tensile strength of the composite material while improving the conductivity of the traditional copper material. Chemical vapor deposition (CVD) is an important method to prepare graphene/copper composites. In this paper, the influence of CVD process parameters of graphene on the surface of copper foil is studied, which lays a foundation for improving the overall conductivity of graphene copper material. For the preparation of graphene on the copper crystal surface substrate by CVD method, the temperature is more suitable at about 1000 degrees Celsius. Compared with polycrystalline copper foil, the addition of graphene increased the overall conductivity of graphene copper foil by 3.7% IACS. The introduction of large-area and high-quality graphene on the surface of copper matrix is conducive to achieving good electrical and mechanical properties of graphene copper electromagnetic wires for power transformer.

Epoxy resin is one of the primary insulating materials used in high-voltage power equipment due to its excellent insulating properties. This paper investigates the DC conductivity and thermal conductivity of Al2O3/EP composites with 0wt%, 0.5 wt%, 1.0 wt%, and 2.0 wt% Al2O3 content. The experimental results indicate that the conductivity of Al2O3/EP composites increases nonlinearly with the rise in electric field strength, with the optimal performance observed at 2.0 wt% Al2O3 content. Additionally, the thermal conductivity of EP composites gradually increases with the addition of Al2O3. As the temperature increases, the DC conductivity of the 2.0 wt% Al2O3/EP composite also increases. The thermally stimulated current (TSC) test reveals that this is due to the higher carrier concentration at elevated temperatures, which enhances the transport capability of carriers and thereby increases the DC conductivity of the EP composite. The findings of this study provide new directions for the research of novel materials.

As a crucial component in power systems, the variation in hot spot temperatures of T-type cable terminals significantly impacts the safety and reliability of cable operation. Therefore, accurate prediction of the hot spot temperature in T-type cable terminals is significant for preventing faults. This paper proposes a method for predicting hot spot temperatures of T-type cable terminals that based on temperature field simulation and deep learning. Firstly, a finite element simulation model for the hot spot temperature of T-type cable terminals is established, obtaining training samples of hot spot temperatures under various environmental temperatures and load conditions. Secondly, a fusion prediction network structure based on Physics-Informed Neural Networks (PINNs) and Recurrent Neural Networks (RNNs), referred to as the PINNs-RNN network, is proposed. This deep learning model for temperature prediction of T-type cable terminals achieves high-accuracy prediction of hot spot temperatures. The results demonstrate that the proposed PINNs-RNN deep learning model can achieve prediction of hot spot temperatures in T-type cable terminals with higher accuracy compared to traditional deep learning models, which has significant engineering implications for tracing and preventing thermal faults in T-type cable terminals and ensuring the stable operation of distribution networks.

C-GIS (Cubical Gas Insulated Switchgear) is a crucial component in the renewable energy sector. However, the increased deployment of renewable energy sources has exacerbated the issue of overheating at T- type cable terminals, which can lead to damage to C-GIS and negatively impact power supply stability, resulting in economic losses for the power grid. Currently, research on cable terminal thermal faults primarily focuses on insulation interface creepage, temperature monitoring, and improvements in on-site acceptance testing. There is a lack of in-depth analysis on the causes of thermal failures at T- type cable terminals, and the key influencing factors behind these thermal faults have not been clearly identified. To reveal the influence of crimped terminals on the overheating faults of T- type cable terminals, this paper proposes a simplified equivalent modeling method for crimped terminals and uses this method to construct a finite element model of the T- type cable terminals. Finally, by varying the contact coefficient, a simulation analysis was performed to study the impact of contact resistance at the crimped joint on the temperature variation of T- type cable terminals. This provides a simulation basis for analyzing and designing solutions for thermal faults in T- type cable terminals.

With the increasing impact of climate change on the power transmission system, icing monitoring has become one of the key technologies to ensure the stable operation of the power grid. The existing solution is based on the ice cover weighing method for calculating the ice cover thickness. However, over time, excessive ice cover can cause creep of the tension sensor, resulting in inaccurate measurement of the tension value, and the original reference tension is constantly changing. This can lead to the inability to directly monitor the actual ice cover thickness using the weighing method. This study proposes a new method for ice cover monitoring based on tension correction, which significantly improves the accuracy of ice cover thickness measurement by continuously correcting the original tension values. This study includes two innovative icing monitoring techniques: one is tension correction based on temperature regulation, and the other is to correct the current icing value by analyzing the temperature change trend and the previous icing monitoring value when the tension oscillation is not accurate. By analyzing the data and images exported from the installed lines, it has been proven in practice that this method can effectively reduce errors and improve the accuracy of ice monitoring. This study is of great significance for improving the operational safety of the power system under adverse weather conditions.

In the light, economical and compact development of offshore wind power platforms, annular hollow reactors have a broader development space. Due to the special structure of annular hollow reactors, the research methods of dry hollow reactors are no longer applicable. In this paper, the calculation principle of the inductance of the annular hollow reactor is supplemented by the energy method, and the principle of using the flux linkage method to calculate the inductance of the annular hollow reactor is proposed and expounded for the first time. Using Matlab to program energy method and flux linkage method, the inductance of annular hollow reactor with arbitrary parameters can be calculated. The results show that when the number of thread cakes is large, the energy method is more advantageous, and when the number of thread cakes is small, the flux linkage method is more suitable. Therefore, the two methods can be complementary to determine the inductance value of the annular hollow reactor. Based on the finite element simulation results, the optimization direction of energy method and flux linkage method is proposed.

This article conducts in-depth experimental and mechanistic analysis research on the fault problem of multi column parallel overvoltage protection devices in ultra-high and extra high voltage series compensation devices. This type of device has a lower voltage and much lower leakage current than conventional arresters under normal operating conditions, making traditional monitoring methods ineffective. Therefore, once the resistor in a parallel unit deteriorates or malfunctions, it may cause widespread arc flashover, leading to the breakdown of the entire column resistor. This article uses various types of “fault resistor’’ as fault simulation samples, by conducting impulse current tests, the waveform characteristics of current and voltage under different fault states were explored, and the impact of “fault resistor’’ faults on the entire proportional unit was verified. The experimental results show that the presence of “fault resistor’’ significantly reduces the energy tolerance of the device, and the fault develops rapidly, with significant fluctuations in the current waveform. By using polytetrafluoroethylene material to isolate the arc, the arc was successfully prevented from spreading from a single resistor to the entire column, thus avoiding a complete set of faults. The research results of this article provide important theoretical basis and experimental verification for fault warning and design improvement of multi column parallel overvoltage protection devices, and have significant engineering application value.

Transformers are the key elements of power transformer, contributing a significant amount of carbon emissions. Transformer energy-saving and carbon reduction are crucial for the overall energy-saving and carbon reduction efforts of the power grid. The development of conductive materials with high electric conductivity for transformers has attracted much attention. Graphene-copper composites, with their high electric and thermal conductivity properties, are regarded as promising materials acting as conductive material using in transformer. However, up to date, the graphene-copper composites developed in laboratories are mainly in the form of sheet samples, mechanical and heating treatments will be conducted to produce suitable transformer electromagnetic wires. The mechanical and heat treatment may affect the micro-structure and electric performances of graphene-copper composites. In this study, mechanical treatment,i.e. drawing process, and heat treatment (annealing) were performed. The micro-structure of graphene-copper composites were observed by scanning electron microscope technique. It shows that the annealing temperature has a significant effect on the conductivity of the graphene-copper composites.

In wireless power transfer systems, the system is prone to frequency splitting phenomena under the over-coupling and low load resistance conditions. The frequency splitting affects the system power transmission, the transmitted power exhibits a minimum value at the resonant frequency, while the maximum values occur on both sides of the resonant frequency. This paper proposes a method for avoiding the frequency splitting phenomenon based on variable inductors at a fixed frequency. Employing SS topology compensation, variable inductors are serially connected to the primary and secondary sides, and the inductance values are controlled by DC bias current. An equivalent mutual inductance model is used to analyze the impact of driving frequency and variable inductance variations on important parameters such as input impedance and system gains. The MATLAB simulation platform is established to verify the effectiveness of the method, and the experimental results show that the proposed method can improve the system output power under frequency splitting conditions.

The wireless charging system of EV is easily affected by foreign objects, resulting in a diminished charging efficiency, even triggering a series of safety issues. Consequently, detecting foreign objects in EV wireless charging systems has emerged as a pressing issue requiring urgent attention. This paper investigates a method for detecting foreign objects specifically tailored for EV wireless charging systems. This method employs an improved YOLOv8 model, which is modified from the original YOLOv8 model. Firstly, the backbone network of the YOLOv8 model is replaced with the PP-LCNet model. Secondly, deformable convolutions are introduced into the backbone network layers. Subsequently, an SENet module incorporating an attention mechanism is integrated into the neck network section. Ultimately, the initial loss function is superseded by the Wise-IoU boundary loss function. This paper validates the proposed method through simulation. For the collected foreign object dataset, the enhanced model exhibits a 26% decrease in the number of parameters and a 13% reduction in floating-point operations when compared to the original YOLOv8 model, while achieving a 3.1% increase in accuracy over the same baseline.

This paper proposes a bilateral control strategy based on pulse density modulation (PDM) and phase shift modulation (PSM) to achieve maximum efficiency point tracking (MEPT) for S-S compensated wireless power transfer (WPT) systems. Considering the parasitic resistors of coupling coils, an optimal load resistance corresponds to maximum efficiency. However, in practice, it is tough to obtain the optimal resistance due to shifty coupling coefficient and parasitic resistance. The proposed control strategy achieves MEPT precisely without calculated optimal resistance or wireless communication. For the receiving side, in different cases of input current, a semi-controlled bridge rectifier commanded by PSM is employed for stable DC output current. The transmitter adopts a control scheme which hybridizes PDM as well as perturbation and observation (P&O) method. The most efficient pulse density is selected through P&O to minimize input power, which represents the maximum efficiency. A 5-A output simulation model is established to validate the MEPT function of proposed bilateral control strategy.

The power Internet of Things is an important research field of power grids. Compared to ordinary IoT, it has network points with great density and more equipment types, so higher requirements for network management and security protection are needed. In order to facilitate the management of power IoT terminal equipment, it is necessary to fulfill the adaptation of the access equipment protocol. In response to the issue of diverse protocols among different access device manufacturers, this paper analyzes the traffic data of different power IoT terminal communication protocols and constructs a traffic data preprocessing scheme. By parsing the underlying and application layer protocols, effective application layer payload data is extracted. Furthermore, based on the extracted data and preprocessed features, a power IoT terminal protocol classification method based on the Density-Based Spatial Clustering of Applications with Noise(DBSCAN) is proposed. The model obtained from this method can be deployed on the edge or cloud side of power grid, supplying a foundation for the identification of massive power IoT terminal devices as well as their access protocols in the future. The experimental results show that the accuracy of this method is more than 85%.

This paper addresses the issues of low transmission efficiency and poor misalignment tolerance in wireless power transfer for cardiac pacemakers. We propose a wireless power transfer system based on dual-layer magnetic negative (MNG) metamaterials and amorphous nanocrystals. The design leverages the high magnetic permeability and low loss characteristics of amorphous nanocrystals, along with the loss tangent and magnetic loss of the MNG. We conduct system performance and misalignment simulations at 6.78 MHz, demonstrating the system’s efficiency and stability. Comparative experiments between the dual-layer MNG and amorphous nanocrystal system, a traditional system, an amorphous nanocrystal system, and a dual-layer MNG system reveal that the combined dual-layer MNG and amorphous nanocrystal system achieves the highest output power and transmission efficiency of 2.09 W and 82.5%, respectively, when the transmitter (Tx) and receiver (Rx) are 20 mm apart. Furthermore, even with a 20 mm horizontal misalignment, the system maintains an output power of 1.58 W and a transmission efficiency of 62.4%, confirming the superior misalignment tolerance of the dual-layer MNG and amorphous nanocrystal system.

For the WPT system with multiple transmit coils, the coupling channel is filled with energy transfer magnetic field. Although the multi-transmit coil structure improves the system’s anti-displacement ability, the increased contact area also brings the risk of metal foreign objects intrusion. Therefore, based on the principle of detecting changes in the magnetic field, a metal foreign object detection method is proposed to eliminate the detection blind area. By introducing a dual-layer detection coil group, a metal foreign object detection method without blind area is achieved. First, the basic principle of metal foreign object detection is analyzed, and the detection of metal foreign objects is achieved by detecting the change in the induced voltage of the detection coil. Then, the structure of the detection coil group is introduced, including the horizontal detection coil group and the vertical detection coil group, and the detection principle is explained. Finally, the proposed wireless charging system metal foreign object detection method is verified by constructing a radio energy simulation platform. The results show that when the metal foreign object is located at different positions of the detection coil, the horizontal detection voltage, vertical detection voltage, and central detection voltage will change, thereby verifying the effectiveness of the proposed metal foreign object detection method.

Numerous commercial standards for wireless power transfer (WPT) have been proposed to ensure the standardized application of this technology. However, this has significantly narrowed the parameter selection range, forcing a trade-off between efficiency and power. A commercial WPT design scheme for mobile phone is selected as an example to analyze the reason for low system efficiency of existing solutions. Accordingly, an asymmetric parameter optimization approach is proposed. Experimental results demonstrate that this study can improve system efficiency by approximately 10% under rated conditions, reduce the receiver temperature by 40 °C and maintain consistent output power and efficiency regardless of coil misalignment. This provides a flexible and efficient design approach for portable WPT systems.

This letter describes efficient high-power rectifiers, using a cost-effective AlGaN/GaN Schottky barrier diode (SBD) with accurate extraction of large-signal parameters as the rectifying device. The thin-barrier recess-free GaN SBD exhibits a low turn-on voltage of 0.5 V, a low ON-resistance of 6.2 Ω, a low junction capacitance of 0.28 pF, and a high breakdown voltage of 66 V. A precise equivalent-circuit model is derived by elaborating the measured I-V, C-V data, and S-parameters under different DC bias conditions. For model verification, two separate rectifiers working at 5.8 GHz and 10 GHz are fabricated. The measured results indicate that, with 31 dBm input power, the maximum efficiencies of the two rectifiers are 78.9% and 76.6% at 5.8 GHz and 10 GHz, respectively. The high-power rectifiers exhibit the merits of compact size and high efficiency, indicating great potential for large-scale microwave power transfer applications, such as Space Solar Power Systems.

For WPT systems, when the distance between the receiving coil and the transmitting coil shifts greatly, the efficiency of wireless charging is affected because the magnetic fields between the coils cannot be perfectly matched. In addition, WPT coil excursion can also lead to electromagnetic leakage and heat generation, which can damage the device or reduce the life of wireless charging. Therefore, in view of the influence of coil offset, this paper establishes a coupling model of the multi-transmitter coil wireless charging system, studies the relationship between the current of each transmitter coil and the load position, explores the relationship between the current of the transmitter coil and the position of the receiving coil, and proposes a region-based modeling method based on BP neural network, and the prediction error of the optimized region-based positioning model is less than 10 mm, so as to achieve high-precision coordinate prediction effect. The above concepts are simulated and experimentally verified. The results show that the average experimental prediction error is 10.07 mm, which basically meets the set 10 mm positioning accuracy, and the simulation and experimental verification meet the set requirements.

This paper presents a compensation topology identification method based on DC input voltage and current. The method only uses the DC input voltage and current of the inverter to identify the compensation topology of the wireless charging system. Firstly, two wireless power transfer (WPT) system models were established, one with an S-S compensation topology and the other with an S-LCC compensation topology. Then, the relationship between DC input voltage and input current of inverter is deduced according to the model. In view of the charging characteristics of constant voltage wireless charging system, the soft start process is divided into two stages, and the specific compensation topology is identified by comparing the relationship between the DC input voltage and the input current of the inverter in the two stages. Finally, the prototype of WPT system is built, and the effectiveness of the method is verified by simulation. The results show that this method can identify the compensation topology accurately using only the primary DC parameters, which is helpful to the research and analysis of wireless charging system interoperability.

Due to the influence of distance variations and parasitic parameters, it is difficult for wireless power transfer (WPT) systems to maintain a controllable constant voltage output. Therefore, it is crucial to add appropriate control strategies to address the issue. Fractional-order devices have attracted attention in the field of power electronics due to their higher degrees of freedom. A passive fractional-order capacitor (P-FOC) has been proposed to clamp the current phase in the WPT system by adjusting its voltage phase angle. In this paper, a fractional-order WPT system based on a P-FOC has been proposed with controllable constant voltage (CV) output. And the soft switching operation can be maintained during the charging process. Meanwhile, the system performance from the perspectives of device stress and power loss has been analyzed. Through verification experiments on a 200W prototype, the results show that by adjusting the phase angle of the proposed P-FOC, the load/distance independent controllable CV output in the proposed WPT system can be achieved. And the optimal efficiency measured under heavy load reached 94.3%. Finally, theoretical analysis and experimental verification have confirmed the feasibility of the proposed scheme.

This paper addresses the problem of large differences in transmission efficiency between different horizontal positions of multiple loads, and finally to improve the coil’s ability to resist horizontal offset, and an edge-enhanced uniform magnetic field distribution coil is proposed. The design solution is proposed. In order to further improve the transmission efficiency of the system, a uniform magnetic field distribution coil with high transmission efficiency is proposed and simulated and analyzed using Ansys Maxwell software. The edge-enhanced uniform magnetic field distribution coil has a maximum reduction of 27.6% in coupling coefficient decay; the high transmission efficiency uniform magnetic field distribution coil has a 21.4% increase in coil coupling coefficient compared to the planar spiral coil and a maximum reduction in coupling coefficient decay of 20.1%.

As the popularity of electric vehicles and the development of wireless charging technology have prompted a focus on charging efficiency, determining the optimal charging location has become an important issue to improve charging efficiency and user experience. The aim of this study is to develop a method for predicting the efficiency prediction of wireless charging locations for electric vehicles using Black Kite Algorithms (BKA) and Support Vector Regression (SVR). First, we screened the factors affecting charging efficiency by Spearman’s correlation coefficient to identify the most relevant factors. Then, this paper compares four common prediction methods, including BP, RBF, RF and SVR, and identifies SVR as the benchmark model due to its better performance in charging efficiency prediction. Subsequently, this paper further optimizes the SVR model, examines the effects of two optimization algorithms, BKA and PSO, and finally selects BKA as the optimal algorithm. The effectiveness and practicality of the proposed method are verified through simulation and experiment, and the results show that it has a high prediction accuracy and provides new ideas and methods for the design and optimization of wireless charging systems for electric vehicles.

A novel analysis view on bifurcation-frequency-based S-S compensation for wireless charger is introduced. Tx current stress of conventional leakage-inductance-compensation (LIC), self-inductance-compensation (SIC) and bifurcation-frequency-based compensation (BFRC) are derived theoretically. Simulation models are built to prove BFRC is with the lowest Tx current stress, especially in the case of poor coupling. Lower Tx current stress with lower output power is another benefit of BFRC, which has also been proven.

This work compares different types of laminated soft magnetic cores in inductive power transfer (IPT) applications. Laminated cores are typically made with highly metallic properties. They exhibit high saturation flux density and low hysteresis loss and demonstrate a good potential to enhance IPT applications with high power density and efficiency. Nevertheless, their high conductivity and elevated eddy current loss degrades this potential. In this paper, the typical vertical and horizontal laminated cores are analyzed first based on their unique structure and characteristics. The problems of the two types of cores and corresponding optimization directions are given. Finally, experiments are performed and compared and measured experimentally.

With global warming, there is a growing call to protect the environment. Ship wireless charging, as a clean technology, helps to reduce carbon emissions. However, the existing wireless charging system for ships has the problems of low number of degrees of freedom of charging mechanism, cumbersome charging process and low charging power. In this regard, this paper proposes and realizes a small-scale intelligent ship wireless charging system. It mainly includes: developing a multi-degree-of-freedom robotic arm as a charging carrier; designing a visual control system to realize automatic docking of the charging robotic arm to the ship’s receiving end; and adopting wireless charging based on coupled magnetic field to realize wireless energy transmission. After experimental verification, the wireless charging system for ships proposed in this paper meets the wireless charging requirements of ships in the sea movement state, and improves the safety and convenience of wireless charging.

Due to the humid working environment, shore power systems for ships should eliminate exposed conductors as much as possible. Non-contact wireless charging technology does not restrict the free movement of ships and provides more flexible charging options, making it highly promising in the shore power field. Ships require wireless charging systems to deliver high power while adhering to stringent magnetic field regulations to ensure the safety of personnel. However, existing land-based wireless charging magnetic coupler structures generate strong leakage fields when transmitting high power. To address this safety challenge, this paper proposes a novel ferrite shielding design. By utilizing a new structural arrangement of high-permeability ferrite materials, magnetic field leakage is effectively suppressed during high-power charging of ships. A complementary wireless charging mode is proposed to ensure magnetic field safety under various charging conditions. To demonstrate the magnetic shielding advantages of the proposed structure, an experimental setup for the ship wireless charging system was constructed. The results show that at an operating power of 11 kW, the average magnetic field leakage at a distance of 200 mm from the center of the ship-side coil complies with the stringent 6.25 μT public exposure limit set by ICNIRP (1998), proving the effectiveness of the proposed shielding design. The power density of the coupling mechanism reaches 1.2 kW/dm2.

The use of wireless power supply instead of the traditional slide line power supply for DC servo motor can greatly improve the reliability of the system and reduce the maintenance cost. However, the DC servo motor is often in the start and stop working state, which will cause the wireless power supply bus voltage to rapidly decrease or rise, and even affect the normal operation of the DC servo motor. Therefore, it is of great significance to design a moving DC servo motor wireless power supply system with excellent anti-impact load performance. The system adopts the LCL/S compensation topology, the magnetic coupling mechanism adopts the long-track transmitting and E-type receiving structure, and the digital closed-loop Buck converter is connected in the rear stage to achieve accurate and constant voltage output. Then the output characteristics are analyzed. To verify the theoretical analysis, a prototype of DC servo motor wireless power supply system was built, and a DC servo motor was successfully powered stably. The results show that when the DC servo motor drives the trolley with 11.95kg weight, the energy transfer efficiency can reach 86.89%, and the system can always guarantee the constant voltage.

In the domain of oil field inspection device charging, wireless power transfer (WPT) technology offers a unique method compared to wired alternatives. Nonetheless, it faces interoperability challenges due to the variety of inspection devices. Moreover, lithium batteries within WPT systems require both constant current (CC) and constant voltage (CV) charging in flammable, explosive environments to ensure safety. This paper presents a universal method based on the LCC-S topology where the same primary topology can achieve CC and CV charging for various inspection devices through frequency regulation. Furthermore, the proposed method reduces the input impedance angle without affecting the fundamental CC characteristics, thereby limiting reactive power to enable interoperability. To validate this method, the article constructs WPT charging experimental equipment to charge a drone and a quadruped robot. By regulating the frequency, the system achieves CC and CV charging and zero phase angle (ZPA) operation for the two inspection devices.

Wireless excitation systems can solve mechanical wear problems and address the unreliability of carbon brushes and slip rings in electrically excited synchronous motors (EESMs). As the wireless excitation system rotates at high speed with the motor, minimizing components at the receiver side is crucial for reliable operation. Maintaining a constant excitation current under stable motor conditions is crucial, but load resistance fluctuations complicate this task. Thus, the system requires constant current output for reliability. This paper proposes a new LCC-P compensation topology applied to the wireless excitation system, which eliminates the receiver filtering capacitor and thereby reduces the number of components at the receiver side. The advantages of eliminating the filter capacitor is analyzed in this paper. Then, the working theory of the proposed topology and the conditions for achieving constant output current and achieving ZPA and ZVS are analyzed. Finally, a simulation model is established to verify the performance of the LCC-P topology, and the results demonstrate the advantages of the new LCC-P topology.

This study conducts a thorough investigation of reliability control strategies for orbital Contactless Power Supply (CPS) systems in material handling applications. Existing literature predominantly utilizes a simplified purely resistive load model, which overlooks the impact of the inductive characteristics of motors in actual operating conditions. This often leads to suboptimal control strategy performance in practical applications, necessitating the use of large capacitors at the receiving end to ensure output stability. To address this issue, this paper introduces a more realistic inductive load model and compares the performance of traditional proportional-integral (PI) control systems with novel control strategies. The focus is on assessing the stability and reliability of these strategies under complex electrical disturbances. The results indicate that the new control strategies significantly enhance the system's resistance to electrical disturbances, thereby substantially improving the industrial reliability of the entire handling system. These findings have important theoretical and practical implications for the design and implementation of orbital wireless power transmission systems.

As a wireless power transfer (WPT) system operates for a long period, especially with the presence of coil misalignment, the overheating of the magnetic coupler could reduce stability and rise safety risk of the system. To this end, this paper proposes a digital twin model for the magnetic coupler, with the objective of predicting the coupler’s thermal distribution under various operating conditions. The digital twin model is able to predict thermal change of the magnetic coupler, thus the WPT system can lower or turn-off the power transfer in advance to avoid overheating. Also, it provides a valuable and convenient tool for the optimization of the magnetic coupler considering factors like coil misalignment, ambient temperature fluctuation, and load variation.

Wireless Power Transfer (WPT) technology is widely used in many fields due to its secure, flexible, and convenient characteristics. However, the inherent uncertainty of the coupling area between the receiving coil and the transmitting coil has become an obstacle to its further development. Therefore, applying coupled mode theory to analyze wireless power transfer systems that satisfy Parity-Time (PT) symmetry characteristics is a feasible perspective for understanding the energy transmission process. Coupled mode theory analyzes the coupling coefficient range where it can achieve constant load power and system transmission efficiency with changing the coupling area of the transmitting and receiving coils. In general, a self-excited oscillation control circuit is used to generate a two-level inverter square wave voltage. Correspondingly, it leads to insufficient utilization of DC voltage and Total Harmonic Distortion (THD). Therefore, the transistors have to suffer high voltage stress and loss. Besides, the delay from the sampling circuit cannot be adaptively compensated. More unfortunately, the self-excited oscillation control with a fixed 50% duty cycle cannot be regulated. Hence, a three-level inverter voltage control scheme based on digital control is proposed in this article, which can not only improve the utilization of DC voltage and reduce switching loss and conduction loss, but also modulate duty cycle and compensate for sampling circuit delay using digital control.

In response to the low efficiency and low data transmission rate of long-distanc simultaneous wireless power and data transmission caused by the small coupling coefficient, this paper designs the coupling mechanism and topological structure parameters. Firstly, the output voltage gain and information transmission characteristics are analyzed, and the LCC-LCCC compensation topology is designed to reduce the current and improve system efficiency. Secondly, the mutual inductance is increased by using laminated coils and magnetic cores, and the voltage stress of the coils is reduced by using capacitive segmentation compensation. Then, the information transmission rate and the amplitude of information reception are increased by reducing the number of information circuits and the transient time of the information circuit. Finally, the system achieves simultaneous wireless transmission of 120 W and 4.8 kbps of power and data at a transmission distance of 1 m and a distance-to-diameter ratio of 2, with a coupling mechanism transmission efficiency of 78%.

This paper studies regular polygonal electromagnetic Halbach arrays used as transmitters in wireless power transfer systems. Four polygonal configurations are selected as typical research subjects. Through DC electromagnetic simulations in Ansys Electromagnetic Suite and experiments using practical circuits, this paper confirms the superiority of the proposed structures compared to conventional two-coil systems by generating an improved transmission power, which is 3 to 5 times higher than that of two-coil wireless power transfer systems, and a superior transmission efficiency, which is 5 to 10 times greater than that of two-coil systems, when the transmission distance exceeds 20 mm with a coil height of 50 mm. The average transmission power and efficiency at various z-coordinate positions and their standard deviations were obtained to compare the four selected structures. The ratio of the average transmission power (or efficiency) value to the standard deviations of each structure is analyzed quantitatively. The quantitative analysis reveals that, for polygonal EHA structures with uniform coil parameters, the pentagonal Electromagnetic Halbach Array emerges as the optimal structure in the four selected structures.

In this paper, a microwave rectifier which based on adaptive power distribution network (APDN) is proposed. The rectifier employs two cells, one suits low input power, and another suits high input power. With APDN, the rectifier has the ability to distribute the RF input, make two rectifier cells operating at suitable input power level. In this way, high RF-DC power conversion efficiency (PCE) could achieve in a wide RF input power range. For validation, the proposed rectifier at 10 GHz is designed. According to the simulation result, with the input power range from 5 dBm to 23 dBm, the PCE is over 50%. The best PCE is found at 16 dBm, which up to 65%.

Wireless power transfer (WPT) technology is a promising and effective solution to light supply for photobioreactor. However, the misalignment tolerance is the most demanding challenge. In this article, a wireless power transfer system for photobioreactor with novel coupling structure is proposed. A split solenoid coupler and suspended structure are utilized in the transmitting coil and receiving coil, respectively. The number of turns as well as the spacing of the transmitting coil are optimized to obtain a stable mutual inductance when misalignment occurs. The feasibility of the proposed wireless power transmission system is verified by experiment.

Underwater wireless power transfer (WPT) has become one reliable and safe method of charging autonomous underwater vehicles (AUVs). The transmission efficiency of the traditional single-coil structure will significantly decrease as the load value or transmission distance fluctuates. To achieve relatively high transmission efficiency over a wide range of transmission distances, a novel electromagnetic Halbach array (EHA) structure is constructed and analyzed. Both EHA and single-coil structures are modeled using the electromagnetic finite element analysis software ANSYS, upon which experiments are conducted using prototypes. The power transfer performances in the three environments (air, tap-water and seawater), different transmission distances and working frequencies are compared. The experimental results indicate that 150 kHz is the optimal working efficiency for both structures. Also, it is found that in underwater environments, the transmission efficiency is lower compared with that in the air, with around 5% decline in the EHA structure and more than 10% decline in the single-coil structure. Hence, EHA structure has better transmission performance than single-coil structure regardless of the power transmission medium.

The complex environment of high sea conditions will lead to dynamic misalignment of the magnetic coupling structure of the underwater vehicle wireless charging, which can cause the charge of key parameters such as mutual inductance and reflection impedance, and lead to the decline of the efficiency and stability of the wireless charging system. To address this problem, a bidirectional wireless power transfer (WPT) system with input-series - output-parallel (ISOP) connection is proposed. This system is characterized by strong anti-misalignment in various directions under phase-shift control. Based on a clear understanding of the system’s operating principle, the design methods of the arc-shaped coupler and compensation parameters are carried out. Finally, a 1 kW underwater bidirectional WPT prototype is built to verify the feasibility of the proposed solution. Experimental results show that the axial misalignment distance is [−60 mm, 60 mm] and the angular misalignment is [−20°, 20°].

To ensure effective interoperability in electric vehicle (EV) wireless charging systems, a single ground transmitter must seamlessly interface with EV receivers that vary in power class, air gap, and circuit design, facilitating reliable and efficient charging. However, achieving optimal efficiency across different power levels, air gaps, and circuit configurations presents a significant design challenge. This study addresses this issue by exploring EV wireless charging systems configured with two distinct topologies: LCC-S and LCC-LCC. Using the transmitter coil dimensions specified in GB/T 38755.6 as a guideline, the research enhances transmission efficiency and optimizes system parameters by adjusting the resonant inductance of the transmitter and the system’s coupling coefficient. Two receiver units with different power ratings (11 kW and 22 kW), circuit topologies, and air gap settings are designed. The proposed interoperability approach for EV wireless charging systems is validated through simulation, confirming its feasibility.

This paper proposed a novel optimization strategy for coils used in wireless power transmission and provides magnetic field compensation based on Electromagnetic Halbach Array coils with its auxiliary coils using non-uniform distribution. The main coil is fixed, and the positional distribution of the auxiliary coil is optimised by successive superposition to obtain a uniform magnetic field distribution with enhancement on the upper side of the main coil and weakening on the lower side, which guarantees uniform power transmission regardless of the position of the receiver coil. The attenuated magnetic field distribution ensures that the energy transfer efficiency on the upper side of the main coil is not affected by the excess magnetic field energy distribution on the other side. After simulation, it is found that the upper side coils are densely distributed at the two sides, and sparsely in the middle; the lower side are similar to Helmholtz coils.

The multi-objective optimization algorithm based on the target area is used to improve the ability to prevent misalignment of the laminated coupler in wireless charging systems. Firstly, the wireless charging system with S-S compensation and the principle of the stacked magnetic coupling are analyzed. Secondly, the principle of the multi-objective optimization algorithm based on the target area is analyzed and used to optimize the parameters of the stacked magnetic coupling structure. Finally, simulation experiments verified the feasibility of the proposed method.

Stationary wireless charging, where the position of the receiver is fixed, has been widely used, like high-end smartphones. As for dynamic wireless charging (DWC) technology, devices, such as electric vehicles and automated guided vehicles, can be wirelessly charged when they are moving. Therefore, working efficiency can be improved dramatically. One of the most important issues for DWC technology is to optimize the coupler. A good transmitting coil array can generate a uniform magnetic field, which means a lower fluctuation in system output. In this paper, a T-shaped transmitting coil array is proposed for the DWC system, which features a lower output variation and is convenient for splicing and extending. The finite element simulation illustrates that the magnetic flux density of the T-shaped transmitting coil array is more uniform than that of the traditional square transmitting coil array. In addition, experimental results show that the output voltage variation of the T-shaped transmitting coil array is 13%.

A uniform dense coil array structure working at the frequency 13.56 MHz is proposed to enhance the transmission efficiency of wireless power transfer (WPT) systems. The proposed coil array consists of eight identical triangular coils and nested inner and outer driving coils, positioned on a dielectric substrate upper and lower layers. Four of the triangular coils are concentrated at the center of the substrate to enhance the magnetic field at the central position, while the other four coils are located at the corners to ensure uniformity of the magnetic field. Simulation results show that the proposed WPT system achieves an efficiency of 88.5% when fully aligned, 72.4% at a lateral misalignment of 50 mm, and 81.0% at an angular misalignment of 50 $$^\circ $$ ∘ , all of this higher than the transmission efficiency of conventional coils at the corresponding positions. Additionally, the transmission efficiency remains consistently higher than that of conventional coils within the ranges of lateral misalignment from −45 mm to 45 mm and angular misalignment from $$\theta $$ θ = −50 $$^\circ $$ ∘ to $$\theta $$ θ = 50 $$^\circ $$ ∘ .

Magnetic coupled wireless power transfer (WPT) technology has significant research and application value in special scenarios such as underwater charging, biomedical applications, and conductive slip rings for satellite. Traditional contact-based satellite conductive slip rings face issues like short circuits caused by the accumulation of conductive particles. The contactless nature of WPT systems can replace conductive slip rings to resolve this issue. To ensure that the satellite circuits can perform properly, it is critical to address power electronics failures within the WPT system itself. Therefore, designing WPT systems with fault diagnosis and fault-tolerant control functions is crucial for the large-scale application of WPT technology and represents the future development trend. This paper briefly explains the causes and types of faults in WPT systems. Using the LCC-S resonant topology as the research object, a fault dictionary is established based on the fault dictionary method for potential faults in the WPT system with LCC-S compensation. A fault-tolerant control scheme is designed for the more severe faults. Finally, a WPT experimental platform with an output power of 2.0 kW is built. The system efficiency reaches 91.0% without fault tolerance protection and 88.4% with fault tolerance protection.

A flexible harvesting metasurface operating at 2.45 GHz has been developed for microwave wireless energy transmission. This design employs flexible materials such as EGaIn and polyimide, utilizing an orthogonal cross structure for feed coupling, which enhances the metasurface’s adaptability in complex environments while achieving high harvesting efficiency. Simulation results indicate that at the frequency of 2.45 GHz, when the incident wave is perpendicular, the absorption efficiency reaches 99%, while the harvesting efficiency is 82%. The harvesting efficiency can exceed 75% across various bending conditions. Measurement outcomes demonstrate that the harvesting efficiency remains above 60% under different incident angles. The proposed flexible metasurface has been fabricated and tested, showcasing its potential applications in wireless energy supply for dynamic targets.

In the domain of dynamic inductive wireless power transfer (DIWPT) systems, designed specifically for electric vehicle (EV) applications, extensive discussions have focused on unipolar coil structures. The DD coil configurations have been recognized for their better suitability in DIWPT applications. However, the challenge of reducing cross-coupling and mutual inductance effects among transmitting units remains essential for maintaining system robustness and ensuring stable, efficient power transfer under dynamic conditions. This article proposes a novel DIWPT magnetic coupler with a staggered transmitter and receiver configuration to address these issues. This design aims to minimize cross-coupling and mutual inductance while maintaining stable mutual inductance across the transition region, thus promoting high-efficiency power transfer and consistent performance. To validate the effectiveness of the proposed magnetic coupler design under DIWPT conditions, this research utilized the finite element analysis (FEA) tool, Maxwell, to confirm changes in mutual inductance and to optimize coil turns and structural design for improved magnetic coupler performance. Additionally, a comprehensive 2.8 kW system with a average efficiency of 95% was simulated using MATLAB Simulink to verify the operational integrity of the proposed DIWPT magnetic coupler.

There have been many achievements in the research of wireless charging technology for electric vehicles, but due to large project investment, the need for redesign of vehicle charging lines, and imperfect standards and systems related to wireless charging, the industrial application of wireless charging for electric vehicles is rare. And there is no large-scale application in China. The paper used the investment income method of engineering projects to analyze the economics of the industrialization of wireless charging for electric buses in a capital city in northwest China, drew a cash flow statement, calculated the investment payback period under three different states of wireless charging for electric buses, and provided exploratory suggestions for profit models.

In dynamic wireless induction power supply systems, electromagnetic safety assessment is central to the practical application of high-power dynamic inductive power supply systems. The paper firstly derives the current expression for the LCC-S compensation circuit during the coupling process of the dynamic system, and analyses the key factors affecting the magnetic field distribution and the reasons for the transient shocks during the current switching process of the receiving coil. Secondly, in order to reflect the dynamic actual magnetic field distribution, the fitted excitation function is used as the receiving coil current, and the dynamic system is simulated and analyzed by finite element simulation software at seven speeds. Finally, based on the correlation analysis between the sampling points and the measurement area within the magnetic field sampling area based on Pearson’s formula, key measurement points for assessing the electromagnetic field strength within a specified area of a dynamic inductive power supply system are proposed.

The simultaneous wireless power and information transfer (SWPIT) technology has higher security and stability for the charging system of downhole intelligent valve controller. In order to realize efficient power transfer and stable communication under load variation and coaxial separation of magnetic coupler, a SWPIT system based on hybrid topology and decoupling magnetic coupler is proposed in this paper. Firstly, a system circuit design based on ISOP type hybrid topology for power transfer and S-S type topology for information transfer is proposed. Then the coaxial loop DD-solenoid coil with three groups of coils decoupled from each other is proposed to realize the decoupling of power and information transfer respectively. On this basis, the optimal load of the hybrid topology is derived, and the load matching is realized by the T-type topology. Simulation and experimental results show that the proposed magnetic coupler can realize the decoupling of the coils. The average efficiency of power transfer is 90.03%, and the power transfer has almost no effect on the performance of information transfer.

This paper presents a method to estimate the coupling factor of coil-system during the operating of wireless power transfer system. In this method, the excitation signal is generated by the inverter of wireless power transfer system. The current response to the excitation signal is analyzed in frequency domain to estimate the coupling factor. In this paper, the signal model that utilized to estimate the coupling factor is first derived, which revealed the mathematical relationship between the current response to the excitation and the coupling factor. Second, based on the signal model, the estimation method is implemented and verified in the test bench. The results show that the errors of the estimated values are lower than 0.025 for the coupling factors in the range of 0.2 to 0.4 . The estimation update rate of 500 kHz is achieved. Therefore, the proposed method could be interesting for some WPT applications that need estimated coupling factor in real-time during power transfer.

Electromagnetic metamaterials (EM) have great potential for improving the efficiency of wireless power transfer (WPT) systems. However, the design and development of low-frequency EM for WPT working at kHz frequencies are challenging due to the limitations of wavelength and loss. This paper proposes a new EM structure suitable for WPT system at kHz frequencies. The simulation analysis of the magnetic field focusing characteristics in the WPT system with the proposed EM is conducted. The low-frequency EM model is proposed based on the distribution of magnetic field lines. The parameters of the plane spiral coils and the dual LCC compensation circuits for the WPT system are designed. An experimental platform for WPT with the low-frequency EM is built. The experimental results verify the rationality and feasibility of the low-frequency EM designed in this paper, which is expected to provide an effective approach for improving the transfer efficiency of WPT systems at kHz frequencies.

To achieve high transmission efficiency during the charging process of wireless power transmission systems, the relative position between the primary coil and the secondary coil in the magnetic coupler needs to be kept as constant as possible. However, the offset of the coupler coil is inevitable in practical applications. Therefore, this article analyzes the additional compensation topology of resonant converters, the reasonable selection strategy of resonant parameters, and the influence of parasitic parameters on parameter design. A composite resonant coupler considering the influence of parasitic parameters has been proposed, which has higher anti offset capability. This coupler integrates traditional BP couplers and a simple series series topology structure, thus achieving numerical decoupling of the primary and secondary mutual inductance of the magnetic coupler. On the basis of a composite resonant coupler, a field circuit coupling model of an anti offset system is constructed, and the influence of parasitic parameters on the anti coil offset ability, constant voltage output ability, and overcurrent protection ability of the magnetic coupler is analyzed. This study provides a theoretical basis for further improving the system's anti offset capability.

Brushless synchronous starter/generator (BSSG) is widely used in aircraft. However, the traditional main exciter (ME) of BSSG is a bulky radial flux machine. What’s worse, a resolver is usually installed to acquire the rotor position of BSSG for starting control. As a result, the power density and reliability of BSSG is decreased. To solve these problems, a high-frequency PCB axial flux ME is designed in this paper for simultaneous rotor position information and power transfer. The distributed three-phase stator and rotor winding topology of ME is designed for PCB layout and the inductance of the windings is extracted using finite-element analysis. Then, a reliable rotor position estimation algorithm which introduced error checking mechanism is proposed. Finally, simulation is conducted with parameters of ME and the proposed position estimation strategy. The estimation results show that both the power and the rotor position information are transferred simultaneously. The rotor position estimation error is within 0.5 electrical degree and the power is 750 W.

This paper proposed a new type rotary wireless energy transfer magnetic coupler for a rotating equipment. The proposed magnetic coupler can overcome the shortcomings of the contact slip rings equipped in traditional rotating equipment and reduce the impact of rotating equipment metal shafts on the system, and is characterized by non-contact, high efficiency, wear free, safety and reliability. In this paper, the proposed magnetic coupler is optimized using finite element simulation software, and the circuit model of wireless energy transmission using S-S compensation scheme is given. Finally, the experiments demonstrated that the proposed magnetic coupler achieves 95% high efficiency output under the conditions of rotation and 5kW output power.

This study introduces an innovative design for a totem-pole power factor correction (PFC) circuit that integrates interleaved coupled inductors and operates in a discontinuous conduction mode (DCM). The primary objective is to enhance the power density and efficiency of the PFC circuit, which is traditionally challenged by the hard-switching losses in continuous conduction mode (CCM). The proposed design leverages the capability of DCM to achieve zero current switching (ZCS) for each MOSFET, thereby reducing switching losses and enabling a higher power density akin to CCM operation. The interleaved configuration of the coupled inductors facilitates rapid current commutation, effectively halving the operating frequency of each branch and achieving improved current sharing. The efficacy of this design is substantiated through a 2 kW simulation model, demonstrating a total harmonic distortion (THD) of 4.87%, indicative of high power factor performance.

In the field of Capacitive Power Transfer (CPT) system research, maintaining stable power transmission remains a pressing concern. Misalignment between couplers leads to uncontrollable power transfer, significantly compromising the stability of CPT devices. Furthermore, most anti-misalignment techniques encounter several challenges, such as complex design procedures and the need for multiple compensation components. This paper introduces a parameter design approach tailored for CPT systems by operating the system in a non-resonant state to achieve stable power transfer. The proposed method employs a basic compensation network to address misalignment issues, eliminating the need for active control mechanisms or additional compensation components. To validate the efficacy of the proposed method, a simulation experiment was conducted. The results demonstrate its effectiveness, as power remains stable throughout the misalignment process, and soft-switching capability is consistently maintained.

With the popularization of wireless power transfer (WPT) in consumer electronics, this technology has attracted more and more researchers’ attention in the fields of automobile, aerospace, underwater ships and so on. WPT has become a subversive solution to the pain-point problem of many technical fields. At present, the rotating power supply in the aerospace is mainly realized by slip rings or cables. Slip rings are essentially current-carrying contact mechanical system, with the problems of short circuit and open circuit, which have become a technical bottleneck for long-life and high-reliability aerospace rotating mechanisms. WPT does not have mechanical wear problems and cable-drag problems. In this paper, a wireless rotating power supply system is proposed according to the requirements of space rotating mechanism, achieving an output power of 2.5 kW with an efficiency of 92% each channel.

The rise in temperature in the magnetic coupling mechanism is a critical factor affecting the operational state of wireless charging systems. To obtain a more accurate temperature field distribution in the region of the magnetic coupling mechanism, a numerical study of the electromagnetic-thermal bidirectional coupling process of the magnetic coupling mechanism was conducted using the finite element method. A computational model of the magnetic coupling mechanism was established based on the characteristics of the electromagnetic field and temperature field distributions. This model and finite element calculations determined the losses in the magnetic coupling mechanism. The non-uniform losses from the electromagnetic field analysis were loaded into the temperature field calculation mesh as heat source boundary conditions. Considering the impact of temperature changes on material properties, the temperature field analysis of the magnetic coupling mechanism was realised. The heat source was corrected based on the temperature at each iteration, achieving dynamic bidirectional coupling between the electromagnetic and temperature fields. This method enables rapid calculation of the electromagnetic and temperature characteristics of the magnetic coupling mechanism while ensuring acceptable accuracy, guiding the preliminary design of wireless charging.

With the green grid construction as the guideline, explored in-depth researches and applies the new technology of digitalization and intelligence, with the main line of the whole life cycle management of the power grid, we have been working at full speed in the five directions of integration of design and construction, visualization of education and training, digital intelligence of daily management, modernisation of wisdom construction site, wisdom operation and overhaul, focusing on the use of three-dimensional panoramic design, VR, BIM, 5G, Beidou, digital intelligence system, work method innovation and other advanced methods and technologies, to achieve a leapfrog elevation of the level of power grid construction, go through the application of engineering field practice, having achieved good results, formed a very informative and popularized typical experience, for the construction of digital Intelligence strong power grid provides reference and reference.

This paper analyzes the impact of the transient response characteristics of double-fed induction generators on power-frequency protection from the perspective of phasor extraction. Firstly, it examines the relationship between the transient response of the double-fed induction generator and the rotor-side converter as well as the Crowbar circuit under different fault depths, obtaining the transient response characteristics under various levels of voltage sag. Then, based on the conclusions of the transient response analysis, the paper analyzes the impact of the transient response on AC line differential protection and distance protection under different fault depths from the phasor extraction viewpoint. Scenarios where the protection misoperates are presented, and the reasons for incorrect operations are explained in conjunction with the fault analysis conclusions.

As a bridge between distributed photovoltaic (PV) panels and users, energy storage systems are crucial for balancing supply and demand in village-level microgrids (VMG). However, the current mainstream energy-based lithium battery energy storage system faces the problem of shortened lifetime due to frequent charging and discharging operations. To address this, a hybrid energy storage scheme integrating supercapacitors (SC) and lithium batteries is designed for VMG, and a hybrid energy storage scheduling strategy is formulated, aiming at optimizing the resource allocation of “source-load-storage” to effectively cope with the fluctuation of power supply and demand, and at the same time, reducing the loss of lithium batteries. In order to make full use of the active support capability of supercapacitors and reduce the fluctuation of grid voltage and frequency, an optimization objective of maximizing the sum of virtual inertia time constants of supercapacitors is set in the scheduling strategy. In addition, in order to solve this high complexity model efficiently, a Multi-objective snow geese optimization algorithm (MSGAR) based on enhancing the adaptive behavior of the population and incorporating an external warehouse mechanism is developed. Finally, the effectiveness of the proposed multi-objective optimization algorithm is verified by a case study. The results show that the proposed algorithm exhibits more superior convergence performance on multi-objective benchmarking functions compared to existing evolutionary algorithms.

The fault diagnosis of SF6 gas-insulated equipment is of great significance for ensuring the safety of power grid. Studies have shown that accurate detection of SO2F2, a characteristic decomposition product of SF6, helps to determine the early latent faults of equipment. To this end, this paper studies the SO2F2 detection technology based on laser spectroscopy, analyzes the infrared spectral characteristics of SO2F2 and its coexisting gases, and finds that SO2F2 has a strong absorption peak at 2763 cm−1 and is not interfered by its coexisting gases; a laser absorption spectroscopy experimental platform is built using a 3619 nm ICL laser to carry out quantitative detection research on trace SO2F2. The results show that in the concentration range of 0–600 ppm, the system response of the direct absorption spectroscopy is 0.782 mV/ppm, the repeatability error is 2.267 ppm, and the detection limit is 3.94 ppm; the harmonic modulation method can comprehensively improve the detection performance, with a system response of 11.433 mV/ppm, a repeatability error of 0.977 ppm, and a detection limit of 357.56 ppb. The research results provide theoretical and technical support for on-site charged detection of SO2F2.

Recently, the increasing demand for secure communication links in power transmission and the requirement for online monitoring of transmission lines have led to the extensive use of Optical Fiber Composite Overhead Ground Wire (OPGW) in 500 kV transmission systems. Typically, OPGW is grounded at every tower. Electromagnetic induction causes an induced electromotive force on the ground wire, which forms a current loop between the towers, resulting in induced currents and subsequent power losses. This research develops a 500 kV single-circuit transmission line model using standard tower types to examine the distribution of induced currents and ground currents along the OPGW. The study then analyzes the effects of grounding resistance, span, and conductor transposition on the induced current along the OPGW, the current into the earth, and induced power losses. The results indicate that the span and grounding resistance have a minimal impact on the induced power loss of the OPGW, while the OPGW resistance has a significant effect on the induced power loss.

In the operating environment of high-voltage transmission lines, traditional monitoring methods are often difficult to provide accurate micro-meteorological data due to electromagnetic interference, which seriously affects the safety and stability of the line. The application of insulated optical unit optical cables puts forward higher requirements for the line operating environment requirements. In order to overcome this problem, this study pioneered a new method for online monitoring of microclimate in insulated optical cables. This method achieves high-precision signal collection of micrometeorological parameters by deploying fiber grating sensors, and uses interference demodulation technology to finely process the collected signals. On this basis, we carefully extracted three key features of temperature, humidity and wind speed from the demodulated signals, which can keenly capture changes in micrometeorological conditions. In order to further improve the accuracy of monitoring, we used wavelet neural network to build an intelligent monitoring model. The model takes the extracted features as input and uses a deep learning algorithm to accurately identify and predict different types of micrometeorological conditions. After rigorous testing and verification, our research method has demonstrated excellent performance, with its Jaccard coefficient significantly close to 1. The high value of this indicator fully proves the accuracy and reliability of this method in the field of microclimate monitoring. This innovative monitoring method will provide environmental protection for the application of insulated optical unit optical cables in the power grid, and provide strong technical support for the safe operation of high-voltage transmission lines.

Electric vehicle charging behavior is the basis for accurately predicting charging demand and achieving smart charging. Considering the multi-peak distribution characteristics of the charging behavior time data. An adaptive diffusion kernel density estimation model (ADKDE) based on the diffusion equation is used. Firstly, the Gaussian kernel function is converted into a linear diffusion process using the diffusion heat equation, and the asymptotic mean integrated squared error (AMISE) is used to select the adaptive optimal bandwidth for the diffusion kernel function in order to fit the multi-peak data distribution better. The validation is based on the charging order data of a district in Beijing in 2021. The results show that the adaptive diffusion kernel density estimation model can best track the changes of peaks and troughs of real samples, and has more accurate fitting results for one-dimensional and high-dimensional data.

Researchers from many countries around the world have been conducting direct observation of lightning currents from high towers. However, when the lightning strikes the tall tower, due to the impedance mismatch of the lightning channel, the tower, and its grounding impedance, the lightning current will be refracted and reflected many times in the tower, resulting in unreal current measurements. Based on the transmission line model, this paper analyzes the current distribution characteristics of currents along the tall tower. Current in the tall tower is found to feature (the bottom of the tower is the exception) a secondary peak (typically the largest peak) after the first peak. As the tower height increases, the peak current in the tower decreases. The effects of the top and bottom reflection coefficients of the tower and its height on the current waveforms along the tower are further studied, and the first peak of the current waveform is found to increase with increasing absolute value of the top reflection coefficient. Moreover, the secondary current peak and the amplitude of the pulse also increase with an increasing absolute value of the reflection coefficient. Furthermore, an increase in the tower height will result in longer interval periods of the current pulse and a smaller secondary peak.

As renewable energy penetration increases, Virtual Power Plants (VPPs) must not only manage energy scheduling but also ensure system security, particularly in response to frequency fluctuations. Existing research focuses on optimizing Primary Frequency Control (PFC) and developing specific control strategies for VPP units. In this study, a dynamic simulation model of a VPP was constructed, and two control systems—Energy Management System (EMS) and Capacity Coordinated Frequency Control (CCFC)—were established and optimized for better control effectiveness. The results demonstrate that the EMS designed for rapid energy storage response is better than traditional methods in responding frequency disturbances caused by rapid power demand changes. Under EMS control, the frequency nadir improved by 17.5%, and the time to reach steady-state was reduced by 77.2% during rapid power increases. Similarly, the nadir improved by 17.1%, and the steady-state time was reduced by 69.5% during power decreases. In addition, the coordinated optimization of EMS and CCFC enhances the VPP’s ability to manage large-scale power fluctuations. The safe power step adaptation range is expanded from 5 MW to 25 MW when the BESS’s dispatchable power is limited. This study highlights the potential of integrated control strategies to significantly enhance the frequency regulation and overall stability of VPPs.

A resonant driver circuit and control method for high frequency LLC-DCX converter are researched. Through the combination of multi-coupled winding resonant driver and signal multiplexing, lower driver loss and smaller circuit area are achieved at high frequency. By multiplexing switching point signals of the resonant driver bridge as the lower MOSFET drivers, the lower MOSFETs of the driver bridge are self-driven, and the numbers of the MOSFETs in the resonant driver circuit which need to be controlled is reduced from four to two, which still maintaining the same circuit function. The switching point signals of the resonant driver are multiplexed as the lower MOSFETS drivers of the power train, which reduces the number of coupling windings of the driver circuit, avoids excessive coupling windings which affecting the circuit layout. The optimal design method of excitation inductance of resonant driver circuit is proposed to ensure that the dead time of drive signal generated by the driver circuit matches the power circuit. And the ZVS condition of power MOSFET is still achieved. The working principle and design method of the resonant driver which multiplexing the voltage signal of excitation winding are analyzed in detail, and A principle prototype is made to verify the circuit and design method.

The coordinated operation of integrated electricity and heat system is an effective measure to promote renewable energy integration and reduce carbon emissions. Compared to the heat-driven operation mode, the coordinated operation mode of heat and power systems has gained widespread attention due to its higher flexibility. The traditional coordinated heat and power operation based on centralized dispatch assumes that the electricity and heating systems can share information, but in practice, there are information barriers between the two energy sectors. Furthermore, the coordinated operation of heat and power systems typically centers around the power system, resulting in the heating system bearing more costs, which makes it difficult to effectively incentivize the heating system to participate in coordinated operation. In this regard, from the perspective of maximizing overall system benefits, this study first addresses optimization problem of the coordinated operation through distributed solution to protect the privacy of each entity involved. Then, based on the Nash-Harsanyi bargaining game theory, an incentive mechanism that considers risk preferences is proposed to redistribute benefits for maximizing overall system gains, thereby motivating the heating system to participate in coordinated operation. Finally, the effectiveness of the proposed approach is validated in an IEEE-6 node integrated electricity and heat system through simulations. The results demonstrate that compared to the heat-driven operation mode, the distributed-coordinated operation of heat and power systems with the incentive mechanism reduces the operating cost of the electricity system by 7.5% and increases the profit of the heating system by 57.2%.

With the continuous promotion of the construction of new power systems, the distribution system with the explosive growth of distributed photovoltaic and the emergence of plenty of flexible loads is undergoing profound changes. Regional multi-level power reverse transmission and jumping of power flow have become the new norma, which poses greater challenges to the operation of county power grids. Under the background of the construction of a new power system demonstration zone, this paper proposes a new paradigm of regulation and operation that integrates adjustable resource construction, panoramic perception of active distribution networks (ADC), and multi-level collaborative control to address the issue of high proportion and large-scale activeness in distribution networks. Relying on the intelligent terminals and deployment integrated management and control platform in station area, the sensing and adjustment capabilities of the active distribution network have been enhanced, the on-site consumption of distributed photovoltaics has been promoted.

Combining Si-IGBT and SiC-MOSFET in a hybrid parallel configuration integrates the lower conduction loss characteristics of Si-IGBT with the fast switching and lower losses of SiC-MOSFET. This hybrid approach offers significant advantages in improving the efficiency of power switching devices. However, the effects of different drive delays on switching losses between Si-IGBT and SiC-MOSFET are not well understood. Improper designing results in higher switching losses instead of lower switching losses, which can seriously affect the safety and reliability of the switching device. This work establishes a switching loss analysis model that takes into account the effects of drive delay. Simulation analysis of the switching losses in a hybrid parallel double-pulse circuit with different gate drive time delays for turn-on and turn-off was conducted to determine the optimal delay time for minimizing the switching losses. The simulation results show that under the proposed optimal delay timing, the turn-on losses are reduced by 32% and the turn-off losses are decreased by 67% with respect to the use of Si-IGBTs only.

In the distribution network, the sets composed of the equivalent combinations of multiple different types of equipment form the local areas within each node and among multiple nodes in the distribution network. The sum of the outputs of multiple devices needs to satisfy a series of constraints, and it is usually not the superposition operation of the constraints of a single device, resulting in relatively complex internal operating characteristics in the local areas of the distribution network and obvious spatio-temporal coupling. This paper considers the aggregator form composed of various types of adjustable loads, and solves the output ranges of the equipment cluster at different times through the equivalent aggregation of the outputs of relevant equipment. This method significantly expands the theoretically feasible range of optimal dispatching and provides a necessary guarantee for the effectiveness of the coordinated control of the distribution network.