Journal of Power Supply

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Evaluation and Analysis of Influence of IGBT Characteristic Parameter Identification Accuracy on Parallel Dynamic Current-sharing

JIN Shengchao, WU Wenbao, HUANG Xiaohong, LUO Wei

Journal of Power Supply. 2026, 24(4): 1-10. https://doi.org/10.13234/j.issn.2095-2805.2026.4.1

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The difference in characteristic parameters of an IGBT module is an important factor leading to the difference in control circuit parameters, which has a significant impact on the dynamic current-sharing characteristics of IGBT parallel applications. When the device parameters cannot be changed, some drive compensation control can make up for the influence of device differences on dynamic current-sharing, and the key to this method is accurately identifying the characteristic parameters of the IGBT module. The influence of parameter (e.g., gate resistance) identification accuracy differences on the dynamic current-sharing characteristics is studied when a synchronous pulse-asynchronous drive method is used. The correlation characteristics of characteristic parameters of IGBT devices are studied, and the characteristic models of each parameter and influencing variables are constructed. The working model of PSpice device parallel switch is established, and the variation curve of IGBT device parameters and influence factors is fitted by combining with the device manual data comparison and multi-working condition test parameter correction. Through the parallel switching characteristic experiments on two groups of modules 1 200 V/200 A and 1 700 V/300 A IGBT, the judgment on the influence of the difference in IGBT characteristic parameters on parallel current-sharing was verified. Finally, the influence of the difference in characteristic parameter identification accuracy on dynamic current-sharing characteristics was summarized.

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Design of Transient Enhanced Capacitor-less LDO with Low Power Consumption

TANG Junlong, YU Che, GUAN Hao, ZOU Wanghui, YU Hua

Journal of Power Supply. 2026, 24(4): 11-18. https://doi.org/10.13234/j.issn.2095-2805.2026.4.11

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To solve the problem of poor transient response of a traditional capacitor-less low dropout linear regulator (LDO), a transient enhanced capacitor-less LDO with low power consumption was proposed, which used a push-pull Class AB operational amplifier as an error amplifier to improve the charging and discharging rate of current at the gate of a power tube. In addition, a novel type of transient enhanced circuit was designed in the LDO to detect the fluctuation of load current under the premise of low power consumption and provide extra charging and discharging current for the gate of the power tube, so as to reduce the transient fluctuation of output voltage. Based on the 0.18 μm CMOS process, the circuit, layout and simulation of the LDO were completed. Simulation results show that the output voltage of LDO was 1.5 V in the input voltage range of 1.6-4 V. Under the rated input voltage, the static current was 9.4 μA, the load current varied in the range of 0-50 mA, the output overshoot voltage and undershoot voltage of the LDO were 56 mV and 55 mV, respectively, and the stable time was within 1.7 μs. In the full-load range of 0-50 mA, the output overshoot voltage and undershoot voltage of the LDO were reduced, and the transient performance was greatly improved. As a result, the designed LDO can meet the application requirements.

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Wide-voltage Hybrid Bridge Bidirectional DC-DC Converter

DUAN Shuangming, HAN Yuqi, LI Junhui, ZHAO Zhiqiang, LIU Haojun

Journal of Power Supply. 2026, 24(4): 19-26. https://doi.org/10.13234/j.issn.2095-2805.2026.4.19

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A wide-voltage hybrid bridge bidirectional DC-DC converter is proposed. Compared with the CLLC converter, the proposed converter adds linear bridge arms on both sides, so as to improve its gain range and reduce the switching frequency and feedback current. A dynamic control method of pulse-shift modulation is put forward, which can effectively suppress the overvoltage at the inductor terminal in the energy transmission process. In addition, this method also has a function of control initialization. In all of its operating modes, the converter can realize soft switching. A prototype of a bidirectional DC-DC converter with a wide-voltage hybrid bridge was designed, and the correctness and effectiveness of the proposed converter topology and control strategy were verified by experimental results.

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Fault-tolerant Quad Active Bridge Converter for Bipolar DC System Interconnection

XU Dazhen, MA Jianjun, ZHU Miao

Journal of Power Supply. 2026, 24(4): 27-40. https://doi.org/10.13234/j.issn.2095-2805.2026.4.27

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To achieve efficient and reliable interconnection in bipolar DC distribution systems, a novel fault tolerant quad active bridge (FT-QAB) converter featuring low power conversion stages and its operation control strategy are proposed. First, the operation control strategy for the FT-QAB under normal operation conditions and the fault reconfiguration operation strategy under pole-to-ground fault(PTGF) conditions on the high- and low-voltage side are presented. Second, the power transmission characteristics and zero-voltage switching operation conditions of the FT-QAB converter during normal and fault-tolerant operations are analyzed. In addition, the flow chart of parameter design and control block diagram of the converter are also given. Third, by comparing the FT-QAB topology with the existing typical converter topologies in the case of bipolar system interconnection, the advantages of the FT-QAB converter in terms of efficiency and fault-tolerant operation capability are clarified, which are realized by reducing the power conversion stages. Finally, the effectiveness of the proposed FT-QAB converter topology and its effectiveness innormal and fault-tolerant operation modes were validated by experimental results.

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Improved MMC with Voltage Self-balancing and DC Fault Clearing Capabilities

LIU Wenjun, WANG Yimiao, QIN Zhiwen, CHEN Genxu, ZHAO Yutong, WANG Yaoqiang

Journal of Power Supply. 2026, 24(4): 41-49. https://doi.org/10.13234/j.issn.2095-2805.2026.4.41

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HVDC transmission systems based on modular multilevel converters (MMCs) face many problems, e.g., the DC fault current cannot be cleared by a half-bridge submodule topology, and the submodule capacitor voltage sequencing requires too much computation and high real-time performance of sensors. Aimed at these problems, a modified full-bridge MMC with fault current self-clearing and module capacitor voltage self-balancing capabilities is proposed in this paper. By accessing a branch consisting of two IGBTs in reverse series on the same side of the adjacent full-bridge submodule, a path is provided for directly connecting the capacitors of adjacent submodules in parallel. In addition, its operating modes in different states are analyzed, and the corresponding dynamic distribution voltage balancing control strategy is designed. By adding the parallel operation state of capacitors, the modified full-bridge MMC can realize voltage self-balancing between the capacitors of different submodules on the same bridge arm without monitoring the submodule capacitor voltage, thus effectively reducing the complexity and calculation amount of the controller. Meanwhile, the parallel input of capacitors can also reduce the output from individual capacitors, thereby reducing the capacitor voltage fluctuations. Finally, the simulation results in RT-LAB show that the DC fault current self-clearing and submodule capacitor voltage self-balancing can be realized simultaneously by using the proposed voltage balancing control strategy.

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Novel Active-neutral-point-clamped Seven-level Inverter with Boost and Self-balancing Capability

WANG Lintao, MENG Jikan, LI Yongwei, ZENG Jun

Journal of Power Supply. 2026, 24(4): 50-58. https://doi.org/10.13234/j.issn.2095-2805.2026.4.50

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A novel active-neutral-point-clamped seven-level inverter based on the principle of switched-capacitor is proposed. The operation principle for the proposed topology and the mechanism of self-balancing for capacitors are discussed in detail. Through a comparison with other topologies, the advantages of the proposed topology such as reduced components, higher Boost capability, lower overall voltage stress and self-balancing capability of capacitors are also demonstrated, showing its suitability for distributed generation, electric vehicles and other applications. Finally, the Boost capability of the topology and the self-balancing capability of capacitors were verified by simulation and experimental results.

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Variable-gain Approach Backstepping Sliding-mode Control of DC Microgrid Bidirectional Converter Based on NDO

CHEN Jingwen, WANG Yuan, WANG Fuqiang, WANG Tongxin

Journal of Power Supply. 2026, 24(4): 59-68. https://doi.org/10.13234/j.issn.2095-2805.2026.4.59

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Aimed at the issue of bus voltage instability caused by constant-power load in a DC microgrid, a variable-gain approach backstepping sliding-mode control strategy based on a nonlinear disturbance observer (NDO) is proposed. First, the exact feedback linearization method is used to obtain the standard Brunovsky linear model of a bidirectional DC-DC converter. Second, a backstepping sliding-mode controller is designed to enhance the robustness of the system while reducing its adjustment time. The error variables are linearly combined to form a sliding-mode surface, and the sliding-mode approach law of power-exponential variable-gain is constructed to achieve fast and accurate tracking of the reference voltage. On this basis, the NDO is introduced to estimate the system perturbation in realtime, and the estimation results are compensated to the backstepping sliding-mode controller to further reduce the steady-state voltage deviation of the system. Finally, MATLAB simulations and an RT-LAB HIL platform demonstrate that the proposed control strategy can enhance the steady-state performance of the system and is highly robust with respect to system and parameter perturbations.

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Regulation Strategy for Switching Frequency of Interleaved Parallel Double-tube Forward Converter Based on Maximum Efficiency

XU Anfei, LUO Shuai, YUAN Lei, XI Ziqiang, DING Wei

Journal of Power Supply. 2026, 24(4): 69-77. https://doi.org/10.13234/j.issn.2095-2805.2026.4.69

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An interleaved parallel double-tube forward converter is taken as the research object. First, based on the analysis of its working mode, an expression for the system efficiency is obtained, and the relationship between input voltage and modulation frequency is given. In addition, a system model is built and simulated using the PSIM software. Second, through the analysis of power losses of the transformer and switching tube in the system, an expression for the converter efficiency is established by taking into account the power losses. Third, a frequency adaptive control strategy based on input voltage is proposed, so as to optimize the system efficiency based on the closed-loop control of system voltage. Finally, an experimental platform of an interleaved parallel double-tube forward converter with rated power of 3 kW was set up, and results verified the effectiveness of the theoretical analysis and proposed control strategy.

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Sliding Mode Control of Boost Converter with Constant Power Load Based on Continuous Finite-time Disturbance Observer

MO Minggui, WU Jiarong, WU Weilin

Journal of Power Supply. 2026, 24(4): 78-86. https://doi.org/10.13234/j.issn.2095-2805.2026.4.78

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To enhance the accuracy of power estimation for a Boost converter with constant power load (CPL) and improve the dynamic performance of the converter system, a sliding mode control strategy based on continuous finite- time disturbance observer is proposed. First, a nonlinear mathematical model for the converter system is established, which is further transformed into Brunovsky canonical form using the accurate feedback linearization technique. Afterwards, a disturbance observer is designed to estimate the total power value of CPL. To address the issues related to numerous adjustment parameters and significant output buffeting in conventional finite-time disturbance observers, a hyperbolic tangent function is introduced to design a continuous finite-time disturbance observer. Second, a non-singular fast terminal sliding mode controller is designed for the canonical form to enhance the robustness of the converter system, and the stability of the closed-loop system is proved based on the Lyapunov theory. Finally, both the simulation and experimental results validated the correctness and superiority of the proposed control strategy.

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Research on Interleaved Parallel DC-DC Converter Based on Variable Bandwidth Active Disturbance Rejection Control

WU Fang, LI Yongming

Journal of Power Supply. 2026, 24(4): 87-97. https://doi.org/10.13234/j.issn.2095-2805.2026.4.87

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Aimed at the issues of a long dynamic tracking time and secondary oscillation during load disturbances in interleaved parallel converters, a variable bandwidth active disturbance rejection control strategy is proposed. First, based on the small-signal model analysis, the influence of parasitic parameter perturbations is taken into account in the transfer function, so as to eliminate internal uncertainty disturbances caused by parasitic parameters. Then, starting from the frequency-domain characteristics, the relationship between bandwidth and anti-interference capability is analyzed in terms of stability and anti-interference characteristics. Finally, Monte Carlo experiments were used to test the robustness of the proposed strategy. Simulation and experimental results show that the proposed strategy is superior to double closed-loop proportional-integral (PI) control in target value tracking and anti-interference quality, thus improving the system’s dynamic performance and anti-interference capability.

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Data-driven Subspace-based Islanding Detection Method for Grid-connected Photovoltaic Power Generation System

CHEN Enlian, CHEN Jianmin, ZHANG Yilian, FAN Qinqin

Journal of Power Supply. 2026, 24(4): 98-109. https://doi.org/10.13234/j.issn.2095-2805.2026.4.98

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The grid-connected photovoltaic power generation technology has developed quickly in recent years, but it also poses risks such as the islanding effect. The realization of real-time monitoring of islanding effect is of significance for ensuring the stable operation of photovoltaic power generation systems. Therefore, aimed at the islanding fault of grid-connected photovoltaic power generation systems, a data-driven subspace-based islanding detection scheme is proposed. First, the fundamental wave from the voltage signal and the secondary harmonic signal of voltage at the point of common coupling are taken as the basis for islanding detection, and a voltage fundamental wave output predictor based on the subspace identification approach is designed. An adaptive filter for islanding detection is designed to track the fundamental wave from the voltage signal in real time, and the fundamental wave from the voltage signal is amplified to generate a residual signal. On this basis, an islanding fault detector is designed according to the residual signal and the secondary harmonic signal of voltage, so as to judge whether the system suffers the islanding fault. Finally, the effectiveness of the proposed approach was verified by simulation results.

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Photovoltaic Array Power Tracking Strategy with Improved Levy-flight Grey Wolf Optimization and Variable-step Perturbation & Observation

LIU Baohong, CHEN Bin, QIAN Lifeng, SHI Yinuo, LÜ Li

Journal of Power Supply. 2026, 24(4): 110-121. https://doi.org/10.13234/j.issn.2095-2805.2026.4.110

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Aimed at the problems of slow maximum power point tracking (MPPT) convergence speed, low searching accuracy and susceptibility to falling into local optimum in the traditional grey wolf optimization (GWO) algorithm caused by multi-peak output power of photovoltaic (PV) arrays under partial shadow conditions, an algorithm with an improved Levy-flight GWO and variable-step perturbation & observation (ILGWO-VP&O) method is proposed. During the global searching, a new nonlinear convergence factor is put forward to improve the convergence speed and searching accuracy of the GWO algorithm, and the population with normal distribution is initialized to further improve the searching efficiency. Levy-flight is embedded to increase the randomness of global searching, so as to avoid the local optimum during the searching process. The VP&O method is used in the local searching to quickly capture the maximum power point at the global level. To verify the validity of the proposed algorithm, a PV power generation system was built for different published GWO algorithms and the ILGWO-VP&O algorithm, and these algorithms were experimentally verified. Experimental results show that the proposed ILGWO-VP&O algorithm has the fastest dynamic response speed, as well as the best steady-state control accuracy.

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Fault Diagnosis Method for Photovoltaic Arrays Based on IDBO-LightGBM

WU Yajun, WANG Lu, ZHANG Jinjiang

Journal of Power Supply. 2026, 24(4): 122-132. https://doi.org/10.13234/j.issn.2095-2805.2026.4.122

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To improve the accuracy of fault diagnosis for photovoltaic arrays, a photovoltaic fault diagnosis method based on an improved dung beetle optimization (IDBO) algorithm which is used to optimize a light gradient boosting machine (LightGBM) is proposed. The IDBO algorithm is used to optimize specific hyperparameters in LightGBM, and a fault diagnosis model for photovoltaic arrays based on IDBO-LightGBM is established. To effectively distinguish various faults, the characteristic points extracted from the current-voltage curves are utilized. To validate the effectiveness of the proposed method, simulation analysis is conducted on the model. A comparison is performed among the proposed method, LightGBM algorithm, DBO-LightGBM algorithm, other decision tree algorithms and support vector machine algorithm, and results verify the stability and accuracy of the novel method.

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Model Predictive Control for Wind Turbine Three-level PMSM with Variable Dead-time

XIONG Chuanyu, SUN Liping, HE Shiying, SHU Sirui, LI Zhiwei, LI Dingchen

Journal of Power Supply. 2026, 24(4): 133-140. https://doi.org/10.13234/j.issn.2095-2805.2026.4.133

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The permanent magnet synchronous motor (PMSM) is an important component of high-power fan electric independent variable-pitch systems. When PMSMs are driven with a three-level converter, model predictive control will exhibit drawbacks such as a poor steady-state performance and high computational demand. To address these issues, a simplified strategy utilizing variable dead-time is proposed. First, a reference vector is obtained based on deadbeat prediction. Second, the basic vector that has the smallest Euclidean distance to the reference vector is rapidly identified based on the introduction of an algebraic method, and the optimal basic vector is determined in conjunction with the DC-side capacitor voltage. Third, the dead-zone voltage vector corresponding to this optimal basic vector is calculated, and both of them are considered as the output vectors for the next cycle. In addition, the duty cycle that minimizes the current control error (i.e., the optimal dead-time) is calculated. Finally, experimental results demonstrate the effectiveness of the proposed control strategy.

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Electrochemical Research on Repairing Technology for Substation Decommissioned Batteries

CHEN Chuanmin, WANG Yanjie, CHEN Ruoxi, JIA Wenbo, YU Jinxing, LIU Songtao

Journal of Power Supply. 2026, 24(4): 141-147. https://doi.org/10.13234/j.issn.2095-2805.2026.4.141

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The lead-acid battery is one of the most important DC power sources in a substation, and it undertakes the important responsibility of ensuring the normal operation of a power system. To prolong the battery’s cyclic life and respond to environmental protection policies, the repairing technology for substation decommissioned batteries is gradually becoming popular. A low-cost and convenient repairing method with repair solution was selected, and the electrochemical working environment for the battery’s negative electrode was designed and simulated based on the cyclic voltammetry method. The effects of different types of chemical agents on the charge and discharge capacity of negative electrode were studied, and orthogonal experiments were used to screen out composite activators that have excellent improvement effects on the charge and discharge capacity of negative-electrode. The results are of signify- cance for activating and repairing substation decommissioned lead-acid batteries.

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Analysis of Electro-mechanical Properties of Lithium-ion Batteries Under Mechanical Stress

LI Xin, JIANG Wei, LIANG Nianbo, ZHAO Wei, CAI Xue, CHEN Zeping

Journal of Power Supply. 2026, 24(4): 148-157. https://doi.org/10.13234/j.issn.2095-2805.2026.4.148

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The effects of applied mechanical stress on the electro-mechanical properties of stacked-pouch lithium-ion batteries are comprehensively investigated at the full cell level. A series of characterization experiments of electro-mechanical behaviors were conducted based on two experimental platforms, i.e., a free expansion bench and a constant-displacement fixture. Phase transition-dependent swelling phase diagrams were established by differential voltage, swelling thickness and force curve analysis, effectively correlating the electrochemical phase transition reaction with swelling properties. The effect of C-rate on the swelling thickness and force was concentrated in the Stage 2-2L phase transition phase, while the initial preload force will mainly affect the amount of curve stretching of the swelling force without affecting the shape of the swelling curve. This was mainly attributed to the initial preload force dependence of elastic modulus. As an assemblage of composite porous materials, the cell had stress-relaxed viscoelastic properties, and it was further found that the stress relaxation was correlated with various factors such as SOC(state-of-charge), C-rate and initial preload force. For the electrical properties, it was found that the initial preload force had a significant effect on the maximum available capacity, C-rate capacity and internal resistance. Experimental results show that the ohmic internal resistance decreased with an increase in the initial preload force, but the opposite was true for the maximum available capacity. Therefore, it was inferred that the dependence of the initial preload force for the C-rate capacity was dominated by the maximum avail- able capacity. A full range of electro-mechanical performance analysis plays a key role for batteries in pack applications.

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Improved NGO Optimized MVMD-BiLSTM for Remaining Useful Life Prediction of Lithium Batteries

GUO Xifeng, HUANG Yuhai, SHAN Dan, YUAN Baolong, NING Yi

Journal of Power Supply. 2026, 24(4): 158-168. https://doi.org/10.13234/j.issn.2095-2805.2026.4.158

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To solve the problem of low model prediction accuracy caused by noise interference and capacity augmentation in the remaining useful life (RUL) prediction of lithium batteries, an RUL prediction method combining the parameter-optimized multivariate variational modal decomposition (MVMD) and bi-directional long and short-term memory (BiLSTM) network is proposed. Multiple health factors (HFs) are extracted from the charging and discharging processes of lithium batteries as model inputs, and the northern goshawk optimization (NGO) algorithm is introduced by combining the sine cosine algorithm and the whale spiral predation mechanism, which is used to optimize the MVMD parameters. Then, the optimized MVMD is used to decompose the HF into a number of smooth components. Finally, the optimized multilayer BiLSTM is used for prediction, and the stacked summation is the final RUL result. The results of a comparative analysis of the proposed method and other methods based on NASA and CALCE data sets show that this method has higher prediction accuracy and generalized adaptability.

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Research on Fault Diagnosis Method for Lithium-ion Battery Based on Variational Mode Decomposition and Random Forest

WANG Junrui, JI Changjiang, LI Jin, TAN Lu, ZHU Xuqiang

Journal of Power Supply. 2026, 24(4): 169-177. https://doi.org/10.13234/j.issn.2095-2805.2026.4.169

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To ensure the safe operation of energy storage power stations and new energy vehicles, aimed at the thermal runaway phenomenon caused by internal short-circuit faults in lithium-ion batteries, a fault diagnosis method based on sparrow search algorithm optimized variational mode decomposition (SSA-VMD) and random forest (RF) algorithm is proposed. First, SSA is used to find the optimal parameter combination of VMD decomposition layer K and penalty factor α, and the internal short-circuit fault signal and normal signal of lithium-ion batteries are decomposed into multiple intrinsic mode functions (IMF). Second, the sample entropy value of each IMF is calculated as an eigenvector. Finally, the eigenvectors are input into the support vector machine (SVM) fault diagnosis model and the RF fault diagnosis model for fault diagnosis, respectively. Results show that the fault diagnosis rate of the SVM model is 66.667 0% and that of the RF model is 96.666 7%, indicating that the internal short-circuit fault in lithium-ion batteries is effectively identified.

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Estimation of State-of-health for Cascaded Utilized Lithium Batteries Based on Pulse Voltage and CNN-GRU

YANG Chuankai, LIU Haolu, YANG Yichen, FAN Yu, ZHANG Huiying, SHAO Jianwei

Journal of Power Supply. 2026, 24(4): 178-187. https://doi.org/10.13234/j.issn.2095-2805.2026.4.178

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Aimed at the difficulties and lack of precision in the online estimation of state-of-health (SOH) for cascaded utilized lithium batteries, an estimation method based on pulse voltage and hybrid neural network is proposed. Based on the battery pulse voltage response curve, this method extracts the slope of terminal voltage and the corrected standard deviation which are related to battery SOH degradation as health features. By integrating convolutional neural networks (CNN) and gated recurrent unit (GRU), the online estimation of SOH for cascaded utilized lithium batteries with high accuracy and high stability is realized. A platform for a battery testing system was established to validate the proposed SOH estimation strategy for cascaded utilized lithium batteries. Resultsindicate that the proposed method excels in real-time accurate estimation of lithium battery SOH, and both the average absolute error and root mean square error are controlled within 0.01, demonstrating excellent generalization capability and robustness.

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State-of-charge Prediction of Electric Loader Batteries Based on CNN-BiLSTM-Attention

DING Wei, ZOU Fumin, LIU Jishun, ZHANG Cheng

Journal of Power Supply. 2026, 24(4): 188-195. https://doi.org/10.13234/j.issn.2095-2805.2026.4.188

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To accurately predict the state-of-charge (SOC) of electric loader batteries, a prediction model com- bining convolutional neural networks (CNN), bi-directional long short-term memory (BiLSTM) network and attention mechanism was proposed. First, the Pearson correlation coefficient analysis method was used to filter the input features; second, the spatial features were extracted by CNN; then the extracted feature sequences were input into the bi-directional LSTM layer for time series modeling, in addition, the attention mechanism was fused to allocate weights, so as to enhance the important features; finally, the prediction results were output by the fully-connected layer. Experimental results show that the prediction accuracy of the CNN-BiLSTM-Attention model reached 99.97%, and the prediction error was within 1.00%. Compared with models such as the CNN-LSTM-Attention model, this model had higher prediction accuracy and smaller error, indicating certain superiority and reliability.

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Predicting SOH of Forklift Batteries Based on CNN Optimized by Whale Optimization Algorithm

XU Zeming, LI Kai’ang, GU Yuqi, ZHAO Chao

Journal of Power Supply. 2026, 24(4): 196-204. https://doi.org/10.13234/j.issn.2095-2805.2026.4.196

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The state of health (SOH) of lead-acid batteries is an important indicator for their reliable operation. A prediction model based on convolutional neural networks (CNN) optimized by the whale optimization algorithm (WOA) was proposed to solve the problem of low prediction accuracy of SOH of forklift batteries. First, CNN was taken as the basic model for the WOA-CNN model. Then, to further optimize the performance of the CNN model, the WOA algorithm was introduced to optimize the weight and bias of CNN by searching the optimal solution in space. To verify the validity of the WOA-CNN method, experiments were conducted using a real data set of forklift batteries. Experimental results show that the WOA-CNN model reduced the mean square error, root mean square error, mean absolute error and mean absolute percentage error in predicting the SOH of forklift batteries by 29.4%, 19.7%, 41.5% and 19.5% respectively compared with the unoptimized CNN neural network, and it reduced these errors by 42.2%, 31.1%, 64.7% and 54.8% respectively compared with the traditional BP neural network, exhibiting smaller prediction errors, higher accuracy and higher stability. The WOA-CNN prediction model provides strong support for the battery health management of electric forklifts, thus extending the battery life and improving the forklift reliability.

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State-of-health Estimation of Lithium-ion Batteries Based on Improved Gaussian Process Regression

DENG Hongli, WU Songrong, LIU Qi, ZHANG Hanwen, LIU Bo, FU Cong

Journal of Power Supply. 2026, 24(4): 205-214. https://doi.org/10.13234/j.issn.2095-2805.2026.4.205

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The accurate estimation of the state-of-health (SOH) of lithium-ion batteries is a basis for ensuring the safe, stable and efficient operation of battery systems. On this basis, a method for estimating the SOH of lithium-ion batteries was proposed based on health indicator extraction and improved Gaussian process regression (GPR). First, the health indicators were extracted from the charge/discharge current and voltage curves, and those with a high correlation with capacity were screened out by Pearson correlation analysis, which were further reduced by an autoencoder deep learning algorithm. Second, GPR was used to establish an SOH estimation model, and the kernel function of GPR was constructed by combinatorial kernel functions. Third, the African vultures optimization algorithm was used to optimize the hyperparameters in the combinatorial kernel function. Finally, the NASA lithium-ion battery dataset was used for model verification, and experimental results show that the proposed method has high accuracy.

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Life Prediction of Power Supply Electrolytic Capacitor Based on IKH-UKF-PF

HAN Xu, ZHANG Jingwei, FU Daiyin, QIN Tuanfa

Journal of Power Supply. 2026, 24(4): 215-222. https://doi.org/10.13234/j.issn.2095-2805.2026.4.215

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It is becoming increasingly important to carry out reliability evaluation on core devices in the electric vehicle charging equipment, so as to ensure the safe and stable operation of the charging equipment. An advanced prediction method is proposed to estimate the state of health of electrolytic capacitor in the power supply which is one of the most important components in the charging equipment, and its remaining useful life (RUL) is also predicted. According to the capacitance loss data, the Verhulst model and exponential model are combined as the final empirical model, and unscented Kalman filter (UKF) is used to generate a recommended distribution of particle filter (PF) to track the degradation path. Aimed at the problem of particle impoverishment, an improved krill herd (KH) algorithm is used to optimize the residual resampling step and improve the prediction accuracy. The results of experiments on the electrolytic capacitor degradation data show that compared with those of the traditional PF algorithm, the root mean square error (RMSE) of prediction result decreases from 2.79 to 0.37 at the prediction time point of 80 h, and the confidence interval width at the 95 % level decreases from 34 h to 4 h. At the same time, compared with that of the KH-UKF-PF algorithm, the RMSE decreases by 27.5%, indicating that the proposed method can provide higher prediction accuracy of RUL.

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Harmonic Suppression Strategy for Medium-frequency AC Collection and Uncontrolled Rectification Transmission System of Offshore Wind Power

YIN Limin, LUN Chenglin, SHAO Xinming, ZHANG Xincheng, LIU Chuang

Journal of Power Supply. 2026, 24(4): 223-231. https://doi.org/10.13234/j.issn.2095-2805.2026.4.223

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With the continuous expansion of the scale and capacity of offshore wind power, the adoption of high-voltage direct current transmission technology has become an inevitable choice for achieving efficient long-distance transmission, in which the use of medium-frequency AC collection with diode rectifier unit (DRU) to achieve high-voltage direct current transmission is considered one of the optimal schemes. However, the nonlinearity of DRU will cause wind power grid-connected converters to generate heavy harmonic currents, which will have adverse effects on the offshore power grid and threaten its safe and stable operation. To solve this problem, a harmonic suppression strategy is proposed for the medium-frequency AC collection and uncontrolled rectification system of offshore wind power. Under this strategy, the grid-connected harmonic current is calculated using the instantaneous power theory in a two-phase stationary coordinate system, and the voltage waveform on the grid side of the wind turbine is actively adjusted by combining with model predictive control (MPC). This can effectively reduce the harmonic current generated by the DRU and ensure the safe and stable operation of the offshore power grid. Simulation and experimental results validate the effectiveness and feasibility of the proposed suppression strategy.

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Impact of STATCOM Response Speed on Grid Voltage and Corresponding Countermeasure

DAI Chaobo, ZHAO Guoliang, YU Hongyang, YANG Zhichang

Journal of Power Supply. 2026, 24(4): 232-240. https://doi.org/10.13234/j.issn.2095-2805.2026.4.232

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To deal with the over-voltage increase at the point of common coupling by the reactive power of a static synchronous compensator (STATCOM) due to its slow response speed when the grid voltage changes rapidly, a general criteria and technical indicators characterizing the over-voltage increase were proposed. Through a simplified analysis based on the magnitude of fundamental voltage, the severity of this over-voltage increase problem due to the slow response speed of STACOM was shown, and the quantitative requirement for calculating the AC voltage became clear. A fast voltage algorithm based on second-order generalized integrator and the corresponding coordination strategy were put forward. The main circuit topology of a STATCOM from a practical project and its control strategy were applied, and the digital simulation results from both a simplified Thevenin’s equivalent circuit and a complicated HVDC benchmark system showed that the proposed fast algorithm and coordination strategy can solve the over-voltage increase problem.

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Research on Modeling and Frequency Coordinated Support Strategy for Island Wind-hydrogen System Under Weak Grid Conditions

LIANG Rundong, MENG Jianhui, WANG Yi, YANG Jian, YU Jie

Journal of Power Supply. 2026, 24(4): 241-250. https://doi.org/10.13234/j.issn.2095-2805.2026.4.241

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Island power supply systems typically exhibit weak grid characteristics, and the system frequency and voltage are prone to losing stability. The coordinated operation and control of wind power and hydrogen energy storage according to different characteristics are key solutions to this problem. On this basis, a grid-forming-based coordinated control method for an island wind-hydrogen system is proposed. By applying hydrogen energy storage into the grid-connected system of grid-forming wind turbines, the load fluctuations are suppressed and the frequency regulation capability of the system is enhanced, thereby improving the system’s frequency regulation capability, safety and stability. First, the wind-hydrogen system in island scenarios is modeled, the grid-forming control of a traditional wind turbine on the grid side is improved, and a grid-forming control strategy considering the output from hydrogen energy storage is put forward. Second, to better achieve the frequency regulation effect of hydrogen energy storage on the system frequency, an adaptive primary frequency control strategy for hydrogen energy storage is designed, so as to realize a wind-hydrogen system frequency coordinated support (WHFCS) strategy for the island wind-hydrogen system. Finally, a system model was built on the RT-LAB real-time simulation platform, and the effectiveness of the WHFCS strategy in supporting the frequency of the wind-hydrogen system was verified through comparison. Results show that the proposed control strategy has good applicability for island wind-hydrogen systems under weak grid conditions, providing a new scheme for improving the reliability and stability of island wind-hydrogen systems.

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Power Sharing of Inverters Considering Uncertain Output from Distributed Generation

YAO Zhongran, SUN Liying

Journal of Power Supply. 2026, 24(4): 251-259. https://doi.org/10.13234/j.issn.2095-2805.2026.4.251

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The islanded microgrid adopts droop control to make inverters share load power according to the capacity proportion of distributed generation (DG), so as to prevent the DG from overload, light load, or generating power circulation. However, the power sharing effect of inverters is related to both the line impedance and the changes in the actual capacity of DG. To solve this problem, an improved droop control strategy considering the randomly changing output from DG is proposed. This strategy adopts two-layer control, in which the outer-layer control eliminates the influence of line impedance in a rated working state. Under changes in the operation condition, the proportion of changed capacity of DG is obtained according to the changes in the voltage of DC bus in a two-stage inverter, and the reference values of power and voltage in a non-rated working state are formulated. In the inner-layer, an improved droop control is adopted to adjust the coefficient of droop control to make the inverters work under the reference value of voltage. Finally, the output from inverters is adjusted to ensure power balance. Simulation results verify the correctness and feasibility of the proposed strategy.

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Linear Fitting Sequential Model-free Predictive Control of Three-level T-type Shunt Active Power Filter

WANG Xuechun, LONG Bo

Journal of Power Supply. 2026, 24(4): 260-270. https://doi.org/10.13234/j.issn.2095-2805.2026.4.260

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The three-level T-type shunt active power filter (3LT²SAPF) has been widely used to improve the power quality of power grid under nonlinear load, and its harmonic suppression and reactive power compensation performance and the corresponding reliability have attracted wide attention. Meanwhile, model predictive control (MPC) can achieve multi-objective optimization. However, once the parameter mismatch occurs due to reasons such as changes in temperature, the output performance of an MPC system will be seriously deteriorated. This may even may endanger the system stability. Additionally, when the circuit relation is unknown, the establishment of a predictive model is not available, and the MPC controller will not be applicable. To solve these problems and enhance the robustness of the 3LT²SAPF system, a linear fitting sequential model-free predictive control method was proposed. First, the principle of linear fitting method for current prediction was analyzed. Second, a current error matrix for each switching vector was established, which can be used for harmonic current tracking. Finally, the cost functions for neutral-point (NP) voltage and DC-bus voltage were designed. The results of numerous experiments under different scenarios verified the correctness and effectiveness of the proposed method.

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Parameter Identification for DC-link Capacitors in TMMC Based on Double-scale Convolutional Neural Network

DAI Zikuo, ZHANG Dongsheng, LIU Shangkun, GUO Ren, CHEN Lijuan, WANG Cheng

Journal of Power Supply. 2026, 24(4): 271-283. https://doi.org/10.13234/j.issn.2095-2805.2026.4.271

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By combing the multi-level technology with the cascade modular technology, the T-cascade modular multilevel converter (TMMC) has characteristics such as 9-level port voltage, redundant switching mode, multiple power ports and hardware multiplexing, and it has become one of the ideal topologies for realizing uninterruptible power supply (UPS) with high power density and high efficiency. However, the large number of DC-link capacitors which are susceptible to failures poses a threat to the reliable operation of TMMC-UPS. Therefore, it is necessary to monitor DC-link capacitors under the scenario of TMMC-UPS to intelligently perceive the changes in the capacitance value and prevent the degradation failure of capacitors, so as to ensure the reliability of UPS. Therefore, a double-scale convolutional neural network model is proposed. By extracting the low- and medium-frequency features of capacitor voltage ripple, both the capacitance value and the equivalent series resistance can be identified, thus improving the monitoring accuracy of capacitor status. The proposed data-driven method does not rely on any mathematical model, and it does not need to add additional measurement hardware either, so it can be easily extended to the parameter identification field of other types of converters.

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Research on Optimization Method for Magnetic Coupling Resonant Wireless Charging Coil

YU Qingchang, LI Haoran, ZHU Yuyu

Journal of Power Supply. 2026, 24(4): 284-292. https://doi.org/10.13234/j.issn.2095-2805.2026.4.284

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In a magnetic coupling wireless charging system, the transmission coil is an important part for improving the efficient transmission of electric energy, and its figure of merit directly affects the efficiency of the whole system. To meet the demand of high-efficiency transmission, first, an equivalent circuit model for an S-S compensation topological system was established, and the relationship between the coil’s transmission efficiency and figure of merit was obtained through theoretical derivation, i.e., maximizing the ratio of the coil’s mutual inductance to its internal resistance can achieve high-efficiency transmission. Then, aimed the mutual inductance and internal resistance which were also the main optimization objectives for coil design, the relationship among the coil’s mutual inductance, internal resistance and geometric parameters was deduced theoretically, and it was further refined into a multi-parameter optimal function problem with constraints between the coil’s efficiency and its parameters. Finally, an iterative solution based on the particle swarm optimization algorithm was proposed, and the winding coils with different specifications were made according to the obtained geometric parameters, so as to test the optimization results.

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PT Symmetric Spatial Wireless Power Transfer System Based on Coil Switching

XU Xingpeng, GUO Feng, HE Xiyu

Journal of Power Supply. 2026, 24(4): 293-302. https://doi.org/10.13234/j.issn.2095-2805.2026.4.293

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In response to the challenges posed by fluctuating load power and reduced efficiency due to variations in the angle and position of a receiving coil, a parity time (PT) symmetric spatial wireless power transfer system based on coil switching is proposed. First, the mathematical model of a cubic structure is established, which is endowed with double-layer space spiral coils on all of its six sides. Simulation results verify that under the condition of equivalent turns and radius, the double-layer coil exhibits a larger inductance and a better coupling performance than the single-layer space spiral coil, and the corresponding design is more compact. Second, the operating frequency and transmission characteristics of SS compensation throughout the whole coupling region are derived. Given the frequency splitting phenomenon existing in the PT symmetric region, a primary-side frequency detection coil switching strategy is put forward to enable adaptive switching in different power supply regions. Finally, experimental validation was carried out, and results show that under specific frequency conditions in a three-dimensional space, the receiving coil can consistently maintain a stable power output of 18 W and an efficiency exceeding 80%, with power fluctuations remaining within 6.7%, thereby validating the effectiveness of the proposed strategy.

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Online Parameter Identification of Permanent Magnet Synchronous Motor Considering Magnetic Saturation Effect

CHEN Geng, YANG Shuying, ZHANG Xing

Journal of Power Supply. 2026, 24(4): 303-312. https://doi.org/10.13234/j.issn.2095-2805.2026.4.303

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Due to the magnetic saturation effect, there is a difference between the apparent inductance and incremental inductance of a permanent magnet synchronous motor (PMSM), resulting in a deviation in the description of the motor model. With the consideration of the influence of magnetic saturation effect, a new PMSM model is established in this paper by introducing apparent inductance and incremental inductance, and the model parameters are further identified by the particle swarm optimization (PSO) algorithm. To solve the problem that the PSO algorithm is easy to fall into local optimum and its convergence speed is slow, an adaptive particle swarm optimization (APSO) algorithm combined with reverse learning is proposed. To overcome the influence of inverter nonlinearity on the identification results, the error voltage caused by inverter nonlinearity is taken as a new parameter to be identified, and it is identified online. Experimental results verified the accuracy of the APSO algorithm when it was used in identifying the d- and q-axis apparent inductance, d- and q-axis incremental inductance, permanent magnet flux linkage and inverter nonlinearity error voltage of PMSM.

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Speed Estimation Method for Permanent Magnet Synchronous Motor with Hall Sensors Based on Least Squares Algorithm and Sliding Mode Observer

ZENG Suicheng, DAN Hanbing, LI Dingwen, SU Mei

Journal of Power Supply. 2026, 24(4): 313-322. https://doi.org/10.13234/j.issn.2095-2805.2026.4.313

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Permanent magnet synchronous motors (PMSMs) have been widely applied in the field of industrial electric vehicles owing to their advantages of high power density, high reliability and easy maintenance. Compared with the PMSM equipped with a high-precision encoder and a speed sensorless algorithm, the PMSM equipped with Hall sensors can guarantee the system’s low cost, as well as its control performance. However, the output information about the position and velocity from low-resolution Hall sensors is of low accuracy when using the vector control method, resulting in motor current ripple and electromagnetic torque pulsation. Therefore, a fusion speed estimation method is proposed, in which the least squares method independent of motor parameters is used to output a continuous smooth angle, and a sliding mode observer based on the motor’s mechanical motion equation is designed to estimate the speed in real time. The motor is started by square wave to solve the problem of missing discrete position, and the designed observer is also proved by the Lyapunov stability method. Finally, experimental results verify the correctness and feasibility of the proposed speed estimation method.

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Reliability Improvement Strategy for Cascaded H-bridge Converter Based on Carrier Reconstruction

JIN Xin, ZOU Zhixiang, LIU Xinlei, GIAMPAOLO Buticchi, MA Ke

Journal of Power Supply. 2026, 24(4): 323-339. https://doi.org/10.13234/j.issn.2095-2805.2026.4.323

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To address the issue of uneven thermal stress distribution in power devices under in-phase disposition PWM (IPD-PWM), an improved carrier disposition PWM strategy is proposed. Aimed at enhancing the reliability of converter systems, this strategy leverages the concept of carrier reconstruction by optimizing the dynamic distribution ranges of modulation waves and carriers. With a focus on balancing the switching losses among submodules, the mechanism by which the modulation wave range influences switching losses at varying modulation ratios is analyzed in depth. The results of Matlab-PLECS co-simulation thermal modeling and experiments on a seven-level converter platform verify that the improved strategy achieves balanced thermal stress distribution in power devices while maintaining output harmonic characteristics identical to those under the traditional IPD-PWM. Consequently, the overall lifetime of the converter is significantly extended.

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Research Progress and Technical Analysis of Coreless DC Transformers

LAI Li, ZHANG Bo, LI Hong, Senior LIN Jingyang, YANG Lun

Journal of Power Supply. 2026, 24(4): 340-352. https://doi.org/10.13234/j.issn.2095-2805.2026.4.340

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As a category of power electronic transformers, DC transformers have demonstrated excellent application prospects. However, the weight and cost of traditional magnetic-core isolation transformers directly constrain the development and applications of DC transformers. Consequently, coreless DC transformers employing lightweight and low-cost coreless isolation transformers have emerged as a new research direction. First, the characteristics of coreless transformers and their functions within DC transformers are systematically reviewed. Second, the technical configurations of coreless DC transformers are analyzed, categorizing them into linear and sinusoidal types. Final, the technical characteristics of three sinusoidal coreless DC transformer variants (i.e., self-inductance resonant, leakage inductance resonant and PT-symmetrical) are examined, and a comparative study of their performance is also conducted.

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30 April 2026, Volume 24 Issue 4