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Table of Content

    30 May 2025, Volume 0 Issue 5
    Research & Analysis
    Research on Early Detection Methods of Short-Circuit Fault in Low Voltage DC Microgrid
    LIU Qitong, MIAO Xiren
    2025, 0(5):  1-8.  doi:10.16628/j.cnki.2095-8188.2025.05.001
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    In order to further improve the sensitivity and reliability of short-circuit fault detection in low voltage DC microgrids,a short-circuit fault early detection method based on voltage and current multi-scale wavelet transform is proposed.Based on the least squares front filtering,fully considering the voltage and current short-circuit fault singularity, the fourth layer wavelet decomposition detail components are used to construct the short-circuit fault early detection criterion.The experimental results show that the proposed detection method is insensitive to the transition resistance. The short-circuit faults can be quickly detected within 0.5 ms when the transition resistance is small.The short-circuit faults can be reliably detected within 0.6 ms when the transition resistance is large.At the same time,it can effectively avoid the influence of disturbing conditions such as frequent load switching, and has better sensitivity and reliability.

    Robust Optimization Scheduling Method for DC Microgrid Considering Probability Characteristics of Source Load Fluctuations
    YU Xueping, LIU Weiling, CAO Bin, XIAO Yuqi, ZHOU Peng
    2025, 0(5):  9-17.  doi:10.16628/j.cnki.2095-8188.2025.05.002
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    The increasing proportion of renewable energy integration has introduced more and more uncertain factors into the operation regulation of DC microgrid.The existing robust optimization scheduling results are too conservative, and the economic performance of the scheduling scheme is poor.Based on the probability distribution characteristics of the typical historical data, a new multi-probability interval uncertainty set is proposed to accurately describe the source and load fluctuations by fitting the confidence intervals of different source and load powers.Based on the proposed novel uncertainty set,a robust optimization scheduling model for DC microgrid is constructed.The column and constraint generation (C&CG) algorithm is used to simplify the model,and an optimization scheduling scheme that takes into account the economy and stability of power grid is obtained.Finally,by comparing the scheduling economy and accuracy of various uncertainty set description methods, the validity and feasibility of the proposed optimization method are verified.

    Research on Establishment Method of Physics-of-Failure Model for Rubber Parts in Connectors Considering Manufacturing Parameters
    CHEN Dongxu, GUO Zijian, XU Le
    2025, 0(5):  18-24.  doi:10.16628/j.cnki.2095-8188.2025.05.003
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    The sealing performance of connectors is the key performance indicator for evaluating their reliability.The sealing performance of most connectors is mainly achieved through the interference fit design of rubber parts.Based on the fluorosilicone rubber standard parts,a study on reliability prediction methods based on the physics of failure (PoF) and quality consistency is carried out.Firstly,the typical failure mechanisms of rubber parts in electrical connectors are studied,and a physics-of-failure model is established.Then,using standard parts, the mathematical relationships between material properties,structural parameters, process parameters,and the coefficients in the physics-of-failure model are studied to establish a transfer model.Finally,the accelerated degradation tests are conducted under the typical stress conditions to verify the effectiveness of the proposed method.The verification results show that the proposed model can accurately calculate the physics-of-failure models of rubber parts with different specifications, with an average accuracy of up to 90%.

    Research on Residual Current Detection Method Based on Tunnel Magnetoresistance Effect
    WANG Genghuan, CHEN Wei, XU Haibo
    2025, 0(5):  25-33.  doi:10.16628/j.cnki.2095-8188.2025.05.004
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    Residual current is an important monitoring parameter in power systems.Aiming at the certain defects existing in the residual current detection methods such as electromagnetic current transformer method and magnetic modulation method when measuring various residual currents,and the respective shortcomings in terms of detection accuracy,sensitivity,zero drift and other performance aspects,a residual current detection method based on the tunnel magnetoresistance effect is proposed.The tunnel magnetoresistive sensor and the average value recognition method are used to measure and identify the waveform of various typical residual currents such as AC and pulsating DC.The influence of some parameters on the measurement is analyzed by building a model and simulation,and the particle swarm optimization algorithm is used to optimize the values of some parameters of the sensor to improve the performance of the sensor.Through experiments,the measurement accuracy reaches 5% and the recognition accuracy reaches 97%.

    Research on Arc Morphology of AC Contactor Interrupting Based on Magnetohydrodynamics
    LUO Yang, YU Xiuyi, JIANG Xuyan, XU Junshuai, CHEN Yuan, LIU Zhenxiang
    2025, 0(5):  34-42.  doi:10.16628/j.cnki.2095-8188.2025.05.005
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    Based on magnetohydrodynamics (MHD) theory, a 3D arc motion model for the dynamic breaking of contacts is established to simulate in the practical industrial products,making the simulation model closer to the real physical conditions of arc interruption.The arc motion process after interruption under different initial currents is analyzed.High-speed photography technology is used to carry out the relevant experiments.The comparison and verification with the simulation results fully demonstrate the effectiveness of the simulation model.Through the simulation study of arcs interruption under different currents,the location and causes of arc stagnation in the structure are pointed out,the reasons for the aggravation of arc stagnation during the interruption of large currents are analyzed,and the theoretical guidance is provided for the subsequent research and development of such products.

    Electrical Design & Discussion
    High Power DC Charging Module Design
    HUANG Ju, YAO Zepeng, ZHOU Junhui, ZHENG Zonghua, MAO Xingkui
    2025, 0(5):  43-51.  doi:10.16628/j.cnki.2095-8188.2025.05.006
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    In high-power applications,the three-phase interleaved LLC resonant converter can effectively reduce the single-phase current stress and the output ripple through the interleaved parallel connection technique,and minimize the size of the output filter capacitor to further improve the power density.The circuit mathematical model for the three-phase interleaved LLC resonant converter is constructed,the key parameters are designed,and the equivalent circuit model is adopted for the theoretical analysis.Mean while the heat dissipation optimization of the magnetic components is taken into account to ensure the conventer’s reliable operation in high-temperature environments.Finally,a 60 kW three-phase interleaved LLC resonant converter prototype is designed and constructed.Through experimental tests,the effectiveness of the proposed scheme is verified,and providing a reference for the design and optimization of LLC resonant converters in high-power applications.

    Design of 2P DC 2 000 V Frame Disconnector
    ZHANG Wenlong, JIANG Guping
    2025, 0(5):  52-55.  doi:10.16628/j.cnki.2095-8188.2025.05.007
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    The 2P DC 2 000 V frame disconnector is suitable for the new generation of new energy systems.For the design of the DC 2 000 V frame disconnector,in terms of the forced isolation of the main arc contact, the insulation parts are added to concentrate the arc on the arc contact, thereby improving the breaking capacity.In terms of reliable control of the contact timing,the appropriate timing difference is determined according to the relationship between the arc column voltage and the residual voltage under different currents,and the influence of contact wear is considered to ensure reliable arc extinction.Combined with high-voltage dynamic insulation simulation and DC arc voltage precise control calculation, the reliability of the product is accurately ensured.Through experimental verification,the new 2P DC 2 000 V frame disconnector meets the requirements of both new and old standards.

    Research on Inrush Current of Capacitor-Switching Contactor
    LI Xinye, CHEN Baisheng, ZHENG Yun
    2025, 0(5):  56-62.  doi:10.16628/j.cnki.2095-8188.2025.05.008
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    When power capacitors are connected to a circuit, a switching inrush current exceeding 200 times the rated current will be generated.The capacitor switching contactor with a current-limiting resistor is often used to suppress the switching inrush current.In order to optimize the suppression effect,the switching inrush current waveform when the capacitor bank is put into operation is studied through the random inrush current suppression experiments,and the primary and secondary switching inrush currents are defined. Three current-limiting resistors with different resistance values are replaced on the same capacitor switching contactor,and the inrush current suppression waveforms are obtained by switching the capacitor banks with the same capacity.The study finds that if the resistance value of the current-limiting resistor is too small,the primary inrush current will exceed the application requirements,if the resistance value of the current-limiting resistor is too large,the secondary inrush current will exceed the application requirements.However,a suitable resistance value of the current-limiting resistor is selected to make the suppression of the primary and secondary inrush currents achieve the expected effect.This provides a reference for the inspection and selection of capacitor-switching contactors and the determination of the resistance value of the current-limiting resistor.

    Design and Research of a Hybrid High Step-Down Ratio DC/DC Converter
    LIANG Huanyu, ZHENG Celin, LIU Xinyi, ZHANG Shilei
    2025, 0(5):  63-67.  doi:10.16628/j.cnki.2095-8188.2025.05.009
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    The switching capacitor step-down topology has the advantages of high efficiency,no need for inductors,and small size.By being connected in series with a Buck converter,it can achieve a high step-down ratio constant voltage output.The working principle of this cascaded topology is analyzed.Under the same operating frequency,by reusing the switching tubes,the number of switching devices can be further reduced to form a hybrid step-down topology structure and achieve the miniaturization of the converter.The proposed topology can significantly increase the duty cycle of the step-down circuit and is suitable for the high step-down ratio application fields.The experimental results verify the correctness of the theoretical analysis.

    Energy Management
    Research on Decision-Making for Renewal of Power Grid Equipment Based on Comprehensive Performance Evaluation
    LIU Boyan, ZHANG Mengmeng, XIANG Jing, HOU Yuwei, XU Jianshu, LIAO Keyi, GUO Jiaxin
    2025, 0(5):  68-75.  doi:10.16628/j.cnki.2095-8188.2025.05.010
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    Aims to develop a scientific and rational decision-making method for power grid equipment renewal to achieve the healthy and sustainable operation of power grid enterprises.Basing on the theory of total life cycle cost (LCC),the Weibull model is introduced to calculate costs,and the time value of money is incorporatd to establish an optimization model.Thereby the optimal economic life and the minimum total life cycle cost are derived.A comprehensive performance evaluation system is constructed from the perspectives of economy,technology,and safety.It covers six indicators such as total life cycle cost and availability.The indicators are quantified through the Analytic Hierarchy Process (AHP) and normalization.Taking the communication line equipment of Company A as an example,the number of the renewal equipment is reduced by 329 km compared with the expected amount,and the equipment renewal budget is decreased by 26.45%.The results show that the proposed model effectively reduces the operating costs of power grid enterprises and enhances the comprehensive performance of the equipment,providing strong support for the equipment renewal decisions.

    Research on Low-Carbon Economic Dispatch Technology for New Power Systems Based on Improved WCVaR Evaluation Model
    LIU Jian, FAN Xinye, QIAO Jibin, LIU Dong
    2025, 0(5):  76-84.  doi:10.16628/j.cnki.2095-8188.2025.05.011
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    Building a new power system with new energy as the main body is the hub platform for the “dual carbon” goal,but the instability of new energy generation brings challenges such as peak shaving and lack of flexibility to the power system.To effectively balance the economy and safety of the system,the following steps are taken.Firstly,the improved Worst Condition Value at Risk (WCVaR) is introduced to quantitatively evaluate the potential risks brought by the uncertainty of new energy output.Secondly,an incentive strategy is introduced to balance the electricity load and optimize and upgrade the peak shaving carbon capture of thermal power units,enhancing peak shaving capacity and new energy consumption level,and alleviating the excessive carbon emissions caused by deep peak shaving of thermal power units.Thirdly,a low-carbon economic dispatch model is established with the goal of achieving comprehensive optimization of system operation costs and operation risks.Finally,the effectiveness of the proposed model is verified through experimental simulations.