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Table of Content

    30 May 2021, Volume 0 Issue 5
    Research & Analysis
    Influence of Vacuum Arc on Anode Ablation with Rotating Contact
    YAN Tianyu, CAO Yundong, FU Si
    2021, 0(5):  1-4.  doi:10.16628/j.cnki.2095-8188.2021.05.001
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    During the vacuum arc breaking process,a large number of particle streams flow toward the anode at a higher bombardment speed,causing concentration of current density on the anode surface,and the anode to heat up.In this paper,a model of anode ablation in the vacuum arcing process with the contact rotating is established,and the deformation,ablation,residual volume and the corresponding temperature distribution changes of the vacuum arc on the anode surface are studied.The temperature distribution and ablation residual volume under the conditions that the contact does not rotate and the contact rotates are compared.The results show that the maximum temperature of anode surface is low and the ablation residual volume is large in the arcing process when the contact rotates.The greater the rotation speed,the lighter the ablation effect of the vacuum arc on the anode.

    Comparative Study of DC and AC Breaking Characteristics
    GONG Zuoyong, XIANG Honggang
    2021, 0(5):  5-8.  doi:10.16628/j.cnki.2095-8188.2021.05.002
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    In the evaluation of DC breaking capacity and low frequency AC breaking capacity,there are general opinions in the industry:AC is easier to break than DC for the same voltage and expected short-circuit current due to the existence of natural zero crossing point of AC.This paper compares and analyzes the degree of difficulty of DC breaking and AC breaking at different frequencies,especially the comparison with AC breaking capacity of low frequency.It is concluded that with the decrease of AC frequency,AC breaking is more difficult than DC.

    Multi-Purchasing Optimization Model Considering Clean Energy Participating in Monthly Contracts
    LIN Fen, LÜ Jun, JIANG Yuewen
    2021, 0(5):  9-16.  doi:10.16628/j.cnki.2095-8188.2021.05.003
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    With the development of clean energy,the issue of clean energy consumption has received increasing attention.This paper considers thermal power,wind power,hydropower (adjustable and non-adjustable) and nuclear power to participate in monthly contract market,and introduces a penalty cost coefficient to quantify the additional costs caused by wind power and non-adjustable hydropower forecast deviations.In addition,this paper also takes into account the relationship between the monthly contract market and day-ahead market,and refines the monthly power purchase optimization to daily.In view of the uncertainty of wind power,non-adjustable hydropower,load and market price,the CVaR is used to measure the loss.The sum of the monthly electricity purchase cost and the day-ahead purchase cost is used as an indicator to evaluate the economy of purchasing electricity,and a model of expected electricity purchase cost-loss risk is established.Based on the analysis of specific examples,the monthly power purchase optimization results are obtained,and the influences of wind power prediction error,penalty cost coefficient and risk preference on the optimization results are analyzed.

    Parameter Optimization for Anti-Migration Performance of Double-Sided LCC Topology
    XU Wenqiang, QIAN Xiangzhong
    2021, 0(5):  17-24.  doi:10.16628/j.cnki.2095-8188.2021.05.004
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    In the traditional wireless power transmission (WPT) system,when the coil is offset,the coil coupling coefficient will change significantly,which will lead to the sharp change of system output power.This problem limits the application and promotion of WPT.In order to solve the problem of output power imbalance caused by coil offset,this paper takes the anti-offset performance of WPT with double-sided LCC topology as the research object,and proposes a method of parameter optimization of compensation network based on PSO algorithm.In this method,two freely adjustable variables are used to optimize the compensation parameters of double-sided LCC,so that the system can automatically adjust the current of transmitting coil and maintain relatively stable output power.Finally,a 200 W experimental prototype is built.When the coil side offset percentage is 40%,the output power fluctuation ratio is less than 10%,and the whole machine efficiency remains above 81%.

    Electrical Design & Discussion
    Application and Structure Design of DC MCB
    LI Min, DAI Ancai, ZHANG Peifu, DING Guohui, LI Yanfeng
    2021, 0(5):  25-29.  doi:10.16628/j.cnki.2095-8188.2021.05.005
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    DC miniature circuit breaker (MCB) is used to provide overload,short circuit,overvoltage and undervoltage protection for clean energy system and various DC loads.Based on that the DC circuit has the characteristics of reasonable selection of critical load current and time constant,this paper starts from the development of DC MCB,first combs the application scenarios of DC MCB,combining with the test situation and test data of key tests,expounds and analyzes its design principle,structural design points,material selection,grounding mode and development trend.

    Design of Intelligent Commutation Switch Based on Parallel-Series Connection
    ZHANG Jianbin, XU Zhihong
    2021, 0(5):  30-36.  doi:10.16628/j.cnki.2095-8188.2021.05.006
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    An intelligent phase changer which can switch phase sequence in real time under load is designed to alleviate the imbalance of three-phase in low voltage distribution network.The device can sample the power network signal in real time and realize phase sequence transformation in short time by controlling the mixed switch composed of thyristor and relay.The cloud platform of intelligent three-phase imbalance management system is developed on the server side,and the phase information,electrical parameters and commutation instructions,etc.are exchanged between general packet radio service (GPRS) and intelligent commutation switch.The network of multiple commutation switches in the cloud platform can form a set of regulation system to improve the ability to control the three-phase imbalance.

    Test and Analysis on Factors Affecting Pull-in Time of AC Contactor
    JI Hua, HE Wei
    2021, 0(5):  37-40.  doi:10.16628/j.cnki.2095-8188.2021.05.007
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    This article verifies and analyzes the factors that affect the pull-in time of AC contactor,mainly including contact bounce,coil parameters,and electrical pure iron grades.By optimizing the contact spring parameters,strictly controlling the force of the contactor contact spring,optimizing and adjusting product coil parameters,and using high-grade electrical pure iron,etc.,it can effectively reduce the pull-in time of the AC contactor and make the suction characteristics of the product better.

    Optimization Design of Electromagnetic System of Hydraulic Electromagnetic Circuit Breaker
    ZHOU Xue, YONG Zhuang, LI Donghui, ZHAI Guofu
    2021, 0(5):  41-47.  doi:10.16628/j.cnki.2095-8188.2021.05.008
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    In order to improve the electromagnetic torque of the hydraulic electromagnetic circuit breaker,a certain type of hydraulic electromagnetic circuit breaker is used as an object for optimal design of its electromagnetic system.First,combined with virtual prototype technology,a three-dimensional physical model of the hydraulic electromagnetic circuit breaker was established according to the product design drawings.Then,considering that the output characteristics of the initial design of the electromagnetic system can not meet the requirements of tripping,the structure of the electromagnetic system of the circuit breaker is optimized based on finite element software Altair Flux,then its output characteristics could meet the requirements of tripping.Finally,the experimental system was built to test the electromagnetic torque of the circuit breaker,which verifies the accuracy of the finite element simulation.By increasing the output magnetic torque of the electromagnetic system of the circuit breaker,the unlocking reliability of the circuit breaker can be improved on the premise that the mechanism locking torque is determined.

    Charging Pile Technology
    Dynamic Fuzzy Control Method of Orderly Charging Based on Vehicle Grid Cooperation
    XIONG Yan, LI Qiangze, FANG Jiakun, FENG Cheng, XU Haibo
    2021, 0(5):  48-54.  doi:10.16628/j.cnki.2095-8188.2021.05.009
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    A fuzzy control model for coordinated and orderly charging management of electric vehicle network under reservation mechanism is proposed.Firstly,the travel chain model of electric vehicle user behavior is constructed,and the Markov process of electric vehicle travel between different destinations is simulated by probability transfer matrix.Secondly,according to the distribution network load forecasting curve and electric vehicle reservation situation,collaborative management is carried out according to the distribution network load margin and electric vehicle charging demand.The charging power of electric vehicle is calculated dynamically.Finally,a simulation example is given to verify the proposed model and algorithm.The results show that the orderly charging management of vehicle network cooperation in this paper can reduce the peak valley difference of distribution network power,reduce the fluctuation of charging power and reduce the charging cost,and the synergistic effect is remarkable.

    Adaptive Flexible Charging Strategy Based on End of Echelon Battery Charging
    LU Qing, XIA Yaojie, YANG Jie, Guang Ruifeng
    2021, 0(5):  55-58.  doi:10.16628/j.cnki.2095-8188.2021.05.010
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    Due to the attenuation of echelon battery,there must be some problems such as short charging time at the end of charging,high voltage slope of single cell and poor economy.In order to improve the economy,an adaptive flexible charging strategy is proposed,which is to optimize the optimal power control point through ant colony algorithm at the end of charging,combine the target charging amount and target slope of single cell voltage at the end of charging,and adjust the charging power by power step.Compared with the charging strategy which uses the fixed threshold of single voltage as the power adjustment point,it has the advantages of longer charging effective time,slower single voltage and more charging volume in the same charging cycle.Finally,the superiority and good effect are verified by the system test.

    Research on Control Strategy of Electric Vehicle Orderly Charging Based on Monte Carlo Algorithm
    LI Hongyan, LIU Miaomiao, JIA Tian, QI Xiaoxiang, NIU Gaoyuan, ZHANG Zhen
    2021, 0(5):  59-64.  doi:10.16628/j.cnki.2095-8188.2021.05.011
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    With the development of electric vehicle industry,the large-scale access to electric vehicle charging facilities will have an adverse impact on the distribution network.This paper proposed a research scheme of electric vehicle orderly charging control strategy based on Monte Carlo algorithm,which not only reduces the adverse impact of electric vehicle load on distribution network,but also achieves the purpose of peak load shifting and valley filling to a certain extent.By building a simulation model in MATLAB/Simulink,the effectiveness and feasibility of the scheme are verified.

    Project Design of Proficiency Testing Related with Charging Connection Control Timing Sequence for Electric Vehicle AC Charging Pile
    YU Wenhui, ZHANG Lu
    2021, 0(5):  65-70.  doi:10.16628/j.cnki.2095-8188.2021.05.012
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    In this paper,the main factors of the measurement results and the causes of dissatisfaction are analyzed when the participating laboratories perform the timing measurement of the charging connection control of the electric vehicle AC charging pile according to the GB/T 18487.1—2015 standard during the implementation of the proficiency testing plan.The main purpose of this paper is to enable the participating laboratories to have a deeper understanding of the technical requirements of the standard.The participating laboratories with unsatisfactory results can find out the problems and take effective measures to rectify them,so as to ensure the accuracy of daily monitoring in the future or obtain satisfactory results by participating in the capability verification again.

    Design of Virtual Matrix Group Controled Charging System for Electric Vehicles
    QI Xiaoxiang, JIA Tian, MENG Fanti, NIU Gaoyuan, WANG Yanming, LIU Miaomiao
    2021, 0(5):  71-74.  doi:10.16628/j.cnki.2095-8188.2021.05.013
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    The group controlled charging system has the function of dynamic power distribution,which can greatly improve the utilization rate of charging modules in equipment and adapt to charging demands of multiple scenes.However,the existing group controlled charging system increases costs due to the use of a large number of power switching devices,which makes it lack of market advantages.This paper proposes a virtual matrix design method for the group control charging system.Taking the 160 kW group control charging system as an example,the system principle,power switch logic,control flow and configuration scheme are studied in detail.At the same time of meeting customers’ demand for charging function and power,the hardware cost of the charger is greatly reduced.And personalized configuration can be carried out according to customers’ demand,which is of great significance to the market promotion of the group controlled charger.A prototype is trial-produced,and the effectiveness of the design scheme is verified.

    Distributed Generation and Grid-Connection Technology
    Energy Storage Control Strategy to Eliminate Risk of New Energy Grid-Connected Operation
    CAO Xinhui, FU Lin, GAO Lingyu, KAI Saijiang, LI Zhongzheng, YUAN Tiejiang
    2021, 0(5):  75-80.  doi:10.16628/j.cnki.2095-8188.2021.05.014
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    Considering the two-way regulation characteristics of the battery energy storage system,a regional power system automatic power generation control model including the battery energy storage system is established.The model tracks the predicted and actual frequency deviations based on the battery energy storage system.The principle of power distribution for frequency control makes the frequency of each area of the power system more stable.Using MATLAB/Simulink simulation analysis,it is verified that the proposed control strategy can realize real-time elimination of new energy grid-connected operation risks,effectively alleviate the pressure of two-way frequency modulation of traditional units,and the frequency of each area is more stable.This strategy has certain flexibility.

    Research on Reliability of Power Supply Based on Islands
    LÜ Haichao, MA Jun, MA Rui, SHEN Zhendong, LI Xinyuan, YU Haoran
    2021, 0(5):  81-85.  doi:10.16628/j.cnki.2095-8188.2021.05.015
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    Traditional island power supply methods mostly use diesel generators to supply power off the grid by themselves or connect to the mainland to supply power via submarine cables.However,it pollutes the environment and is extremely costly.Although distributed power sources have been used in islands in recent years,most of them are isolated islands and off-grid.The stability and reliability of power supply are not good,and a reliable island power supply scheme is urgently needed.Based on this,this article adopts the islands and islands networking scheme,which includes the research of energy controllers and improved droop control of equipment and devices.They coordinate and cooperate with the distributed new energy power generation and fault handling between the islands,which greatly improve the reliability of island power supply.

    Coordinated Dispatch Method of Generation-Grid-Load-Storage Considering Uncertainty of PV Generation
    ZHANG Huaiyu, XU Chaoran, HUANG Zhilong, LU Jianyu, LI Yaping, HOU Yong
    2021, 0(5):  86-92.  doi:10.16628/j.cnki.2095-8188.2021.05.016
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    With the large-scale integration of distributed generation and energy storage system,the problem of coordinated control between different equipment needs to be solved in the distribution network.In this paper,a coordinated dispatch method of generation-grid-load-storage is proposed considering the uncertainty of PV generation and the differential action time scale of different equipment.Firstly,aiming at minimizing power loss and voltage offset,the active-reactive coordinated dispatch model of distributed network is established by considering the coordinated control of generation-grid-load-storage equipment.Secondly,considering the uncertainty involved in distributed generation and load demand,the optimal dispatch problem based on stochastic optimization is established.Typical scenarios are obtained by Monte Carlo simulation and fast forward reduction,and the stochastic optimization problem is transformed into a deterministic optimization problem.Finally,the proposed method is tested on the IEEE 33-bus system,and the effectiveness of the method is verified by comparison.