LOW VOLTAGE APPARATUS

Power Outages Abroad in Recent Years and Lessons to Build New Power System in China

NI Yufan, ZHENG Zhanghua, FENG Limin, SHEN Yukun

2023, 0(5): 1-8. doi:10.16628/j.cnki.2095-8188.2023.05.001

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The major power outage events outside China since 2019 are sorted out,the factors contributing to the events are analyzed,and the potential enlightenment for preventing severe power outages in the future is discussed.According to the analysis,there are four main factors contributing to power outages including the international conflicts and network attacks,the insufficient power supply,the extreme weather,and the equipment failures,which can provide important inspiration and reference for China to build the new power system and ensure the power supply in the future.

Residual Electrical Life Prediction of AC Contactors Based on GA-SVR

GAO Shuyu, LIU Shuxin, ZOU Yanran, JIANG Xingwei

2023, 0(5): 9-14. doi:10.16628/j.cnki.2095-8188.2023.05.002

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In order to solve the problems of single feature selection and low prediction accuracy of residual electrical life prediction of AC contactor,a prediction model was proposed based on genetic algorithm support vector regression (GA-SVR).Firstly,the voltage and current information was collected using the AC contactor full-life test platform and the feature parameters which can characterize the operation state effectively were extracted.Then,the neighborhood component analysis was used to calculate the feature importance,and the optimal feature subset was selected combining with the Pearson correlation coefficient.Finally,the residual breaking times of the AC contactor were used as the life prediction label,and the residual electrical life of the AC contactor was predicted by the GA-SVR method.The case analysis shows that the method has a high accuracy and can meet the actual engineering needs.

Research on Promotion Method of Adjustment-Free Rate for Batch Products Based on Kriging Model and Variation Function

QIAO Yufei, YOU Jiaxin, JIN Xinyu, TU Rui, TAO Ziqi, ZHAI Guofu

2023, 0(5): 15-24. doi:10.16628/j.cnki.2095-8188.2023.05.003

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The acceptability rate of batch products of the balanced force hermetically sealed electromagnetic relay (HSER) in the performance testing after assembly is relatively low,and a lot of adjustment is needed to improve the acceptability rate of products.Four key input parameters are selected through the sensitivity analysis focusing on pick-up voltage and release voltage,which are all related to the permanent magnet.Based on the Optimal Latin Hypercube Sampling method,the sample points of input parameters are selected to establish the finite element model (FEM) of electromagnetic system.The Kriging approximate model is built according to the data of static characteristics.To reduce the error,the Kriging model is modified by using the variation function,and the fast calculation of pick-up voltage and release voltage is realized.By comparing with the finite element model,the accuracy of the fast calculation model is verified.Based on this fast calculation model,the parameter design of adjustment-free rate and tolerance design are carried out.The improvement effect of adjustment-free rate is verified by the actual prototype production.

Analysis of Voltage Imbalance Between Inner and Outer Power Tubes of Three-level Converter

SHANG Yang, WANG Yongsheng, WEI Chao, HUANG Haihong

2023, 0(5): 25-29. doi:10.16628/j.cnki.2095-8188.2023.05.004

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The voltage imbalance between the inner and outer power tubes may occur during the transition between the adjacent switching states of the three-level converter.The mechanism of voltage imbalance is studied.The research results show that the phenomenon is caused by the energy of the distributed inductance in the circuit releasing to the equivalent capacitance between CE of the IGBT.The RC buffer circuit can suppress the above-mentioned voltage imbalance of the inner and outer power tubes.Finally,the principle is analyzed and verified by experiments.

Bipolar Modular Multilevel DC Transformer Based on Magnetic Component Self-Balancing

WANG Fu, LI Zheng

2023, 0(5): 30-36. doi:10.16628/j.cnki.2095-8188.2023.05.005

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The bipolar modular multilevel DC transformer meets the needs of low-voltage users for multiple voltage levels,reliable power supply and power safety.The voltage imbalance and instability caused by the power imbalance between the two DC poles are a technical challenge.A bipolar modular multilevel DC transformer topology based on magnetic component self-balancing is proposed based on a diode-neutral clamped three level half bridge converter.The self-balancing mechanism is described,the current stress on the switching devices is analysed,and an overall control strategy is given.Compared to the additional use of a voltage balancer,it has the advantages of a smaller number of switching devices,a smaller footprint and a higher voltage balancing capability.Finally,a simulation model based on MATLAB/Simulink is built to verify the effectiveness and feasibility of the proposed topology and control strategy.

Research on LED Hybrid Dimming Control Strategy Based on LLC Resonant Converter

CHEN Jiayong, MAO Xingkui

2023, 0(5): 37-40. doi:10.16628/j.cnki.2095-8188.2023.05.006

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In order to achieve wide range dimming of high power LED driver power supplies,the gain offset problem of LLC resonant converters under light load needs to be solved.A novel segmented hybrid control dimming strategy is proposed,which combines the characteristics of the LLC resonant converter controlled by the constant frequency variable duty cycle asymmetric pulse width modulation (APWM) with the voltage reduction control region.When heavy load,pulse frequence modulation (PFM ) control is adopted for LLC resonant converter.When light load,APFM control with duty cycle less than 0.5 is adopted for LLC resonant converter.A high power LED driving power supply prototype with a rated output power of 1 440 W and an output voltage of 30~48 V is built.The experiments show that the prototype had a wide dimming range,fast dimming speed,small current ripple at light load,and stable work,which can verify the correct effectiveness of the new strategy.

Study on Electric Repulsion Force in Circuit of Miniature Circuit Breaker

SHENG Yongbing, ZHAO Ming, SHI Keshao, SU Yanrong, REN Changbin

2023, 0(5): 41-44. doi:10.16628/j.cnki.2095-8188.2023.05.007

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The most important characteristic of a circuit breaker is its ability to turn on and off short-circuit current.In order to improve the breaking performance and reduce the electric power and thermal effects of short-circuit current on other electrical equipment in the power grid,the circuit breaker often has current-limiting performance,and the short-circuit current is limited by rapidly increasing arc voltage.By designing the structure of the loop electric force (Lorentz force) to achieve current limiting,the various structures are analyzed and designed to provide new design ideas for the domestic manufacturers.

Design of Mobile Charging Equipment for Electric Agricultural Machinery

XIA Lili, BIAN Zhaojuan, DONG Anqi

2023, 0(5): 45-50. doi:10.16628/j.cnki.2095-8188.2023.05.008

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Aiming at the inconvenient charging problem of electric agricultural machinery,a mobile energy storage vehicle for agricultural machinery was designed.Meanwhile,the standardized component composition of internal charging piles,charging control software and charging monitoring system were designed.The working process of charging piles for electric agricultural machinery was clarified.The mobile energy storage vehicle has the advantages of quiet environmental protection,environmental friendliness,mobility and high power supply quality.The charging equipment can ensure the healthy and economic development of electric agricultural machinery industry,meet the demand of flexible dispatching,and help the construction of flexible power grid.

Remaining Useful Life Prediction of Lithium Batteries Based on IPSO-LIESN network

LI Xiaohua

2023, 0(5): 51-58. doi:10.16628/j.cnki.2095-8188.2023.05.009

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In order to prevent safety accidents of lithium batteries due to remaining battery life (RUL) and improve the RUL prediction accuracy of lithium batteries,the lithium battery RUL prediction model is proposed based on improved particle swarm optimization (IPSO) algorithm with the leaky integrator echo state network (LIESN).Firstly,its local and global optimization-seeking ability is improved by improving the inertia weights and learning factor update rules.Next,the LIESN network parameters are optimized by IPSO to establish the degradation prediction model.The simulation experiments are conducted using the NASA’s public experimental data of lithium batteries.The results show that IPSO-LIESN has higher prediction accuracy,stability and generalization ability compared with prediction methods such as the fusion of particle fitter and Gaussian process regression (PF-GPR),indirect health indicators and echo state network (ESN) under the same data set conditions,which can demonstrate the effectiveness of the proposed method.

Research on Aviation Battery Fault Evaluation Based on Fuzzy Theory

ZHAN Xiangxin, ZHANG Yuanfeng, HAO Shiyong, WANG Andong

2023, 0(5): 59-64. doi:10.16628/j.cnki.2095-8188.2023.05.010

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In order to study and evaluate the cause of aviation battery fault,the fuzzy theory is used to establish the set of fault symptom factors and the set of fault cause evaluation through the analytic hierarchy process.The fault symptom vector is determined.The primary level fuzzy evaluation matrix and the secondary level fuzzy evaluation matrix are defined.The consistency of the matrix is checked by the nine-scale matrix table of fault factors.The primary and secondary factor weights of the fault factor concentration are established.The feasibility and effectiveness of the fuzzy evaluation model are verified by investigating the fault causes in order according to the size of the membership degree.Finally,the order of occurrence probability of fault causes is obtained.

Research on Aging of Lithium Iron Phosphate Batteries

ZENG Qiquan, ZHANG Shuxing

2023, 0(5): 65-71. doi:10.16628/j.cnki.2095-8188.2023.05.011

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The aging of lithium iron phosphate battery mainly includes calendar aging and cycle aging.The important research progress of aging of lithium iron phosphate batteries is summarized in recent years.The cycle aging mechanism and influencing factors and calendar aging mechanism and influencing factors of lithium iron phosphate batteries are sorted out.The main influencing factors of lithium iron phosphate battery aging is discussed.Calendar aging is mainly affected by operating or storage time,temperature and state of charge (SOC).Cycle aging is mainly affected by operating temperature, charge/discharge rate and depth of discharge.The temperature accelerated aging test can be carried out for LiFePO₄ based on the classical Arrhenius model, but the accelerated aging temperature should not exceed 60 ℃ and the accelerated cycle multiplier should not exceed 3 C.It provides a theoretical basis and design reference for the design of long-life and high-safety LiFePO₄ energy storage system.

Research of Battery Model Based on Multidimensional Table Lookup Method

SONG Dongdong, GENG Lijun, CUI Lina, LÜ Xuejiao, YANG Shuanghan

2023, 0(5): 72-78. doi:10.16628/j.cnki.2095-8188.2023.05.012

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The battery model is widely used in the simulation research of new power system.Based on the equivalent circuit model,to improve the accuracy,considering factors such as aging,temperature,and SOC,the structural parameters of the model were identified offline by conducting multiple linear regression processing on experimental data under multiple operating conditions.An equivalent circuit model based on multidimensional table lookup method was established,and the structure parameters of the model were obtained according to the table lookup and interpolation based on operating data to adapt to changes in battery operating conditions.The correctness of the model and the calculation strategy of non structure parameters SOC and SOH were verified by the design simulation and experimental examples.The calculation results show that the identification results of the model parameters are basically consistent with the transient process of the experimental test,and the correction of SOC using BMS meets the accuracy requirements.The proposed battery model algorithm achieves the expected results.

Optimization of Energy Storage Capacity for Wind Farm Under Multi-Scale Flexible Resource Game

BAI Zhongbin

2023, 0(5): 79-88. doi:10.16628/j.cnki.2095-8188.2023.05.013

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With the grid connection of large-scale renewable energy,the fluctuation and randomness of wind power output need sufficient flexibility resources to meet its grid connection needs.Firstly,the grid connected active power regulation requirements of wind farms are analyzed.Considering the output characteristics and economy of multi-scale flexible resources,an optimization model of wind farm energy storage capacity under multi-scale flexible resource game is proposed.Secondly,NashQ algorithm is used to solve the multi-scale flexible resource game problem and the learning rate of each agent is adaptively optimized,which can improve the convergence speed of the algorithm.Finally,the effectiveness of the proposed model and method is verified by simulation.

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