Table of Content

30 September 2024, Volume 0 Issue 9

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Research & Analysis

Study on Life Prediction of Photovoltaic Inverter Based on Mission Profile

YUAN Juan, CHEN Zhenghao, ZHENG Lianqing

2024, 0(9):  1-7.  doi:10.16628/j.cnki.2095-8188.2024.09.001

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Taking the single-phase single-stage grid-connected photovoltaic inverters as the research object, a life prediction method of photovoltaic inverters based on mission profile was proposed.Taking the actual temperature and light intensity in a year as the mission profile, the IGBT thermal resistance model was imported into PLECS, and the junction temperature data was obtained after several thermal simulations.One year junction temperature profile of IGBT was obtained by the interpolation table lookup method, and the lifetime of individual IGBT was predicted by the rain-flow counting method and the analytical life model.Finally, the life distribution function of a single IGBT was obtained based on Monte Carlo simulation method, and the unreliability distribution function of four IGBTs of single-phase single-stage inverter was obtained by series block diagram method.The predicted results are in line with the actual situation that the service life of photovoltaic inverters is usually less than 15 years.

Fault Ride Through Strategy Based on Virtual Synchronous Generator Control

LI Yanmei, LU Qinghua, LI Tai, HU Yongchang, SU Jinguo, ZHANG Yanhao

2024, 0(9):  8-14.  doi:10.16628/j.cnki.2095-8188.2024.09.002

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Virtual synchronous generator (VSG) technology generates its own phase by simulating the characteristics of the generator, and achieves accurate power output through appropriate phase angles, which has better grid characteristics.Firstly,the basic principles of VSG control is explained,then the causes of overcurrent and instability during power grid faults are analyzed.Based on this,an optimized fault ride through strategy is proposed.This strategy achieves current limiting and voltage support of VSG by calculating the output voltage of VSG, reduces the active power reference value to prevent power angle instability, and introduces a negative sequence current loop to suppress three-phase unbalanced current generated under asymmetric faults.Finally, based on the PSCAD/EMTDC simulation platform,a flexible DC model based on VSG control is built, and the correctness and effectiveness of the proposed control strategy is verified.

Coordinated Control Study on Flexible Interconnection of Distribution Station Areas Considering Transformer Power Losses

LIN Yurun, MIAO Xiren

2024, 0(9):  15-23.  doi:10.16628/j.cnki.2095-8188.2024.09.003

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Aiming at the problems of voltage overrun, unbalanced load in station areas, unbalanced transformer capacity distribution and other problems that occur in the traditional low-voltage distribution network after the large-scale access to low-voltage stations by distributed generator, the power regulation capability of flexible interconnection devices is utilized to construct multi-station interconnections, and a load regulation strategy taking into account the power loss of transformers is proposed to realize the mutual aid of active power and load balancing among the interconnected distribution stations areas.Firstly, the control strategy of the flexible interconnection device with the capacitor current feedback active damping link is introduced to lay the foundation for ensuring the effective implementation of the subsequent load regulation strategy.Then, the load regulation strategy taking into account the transformer power loss is proposed to generate the power command of the flexible interconnection device.Finally, the simulation results show that the proposed strategy can flexibly control the transmission power of the ports and keep the DC voltage at the same time, and can effectively reduce the system loss compared with the traditional load control strategy.

Research on Influence of Installation Methods of Non Nnuclear Battery Cabinets on Seismic Performance

HAN Shuai, LIANG Xiao, RUAN Shanfa, CHU Wenting

2024, 0(9):  24-28.  doi:10.16628/j.cnki.2095-8188.2024.09.004

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Electrical equipment installation is generally categorized into bolt connections and welding.In order to verify the influence of the two installation methods on the seismic performance, two identical battery cabinets are fixed on the vibration table with various installation methods for seismic test.The test results show that the acceleration response of the welded cabinet is greater than that of the bolted cabinet, with higher resonance frequency, smaller displacement of the cabinet, larger overall stiffness, and greater stress of the welding part.However, bolted cabinets are prone to fastening failure of bottom beams, large battery and cabinet deformation and high stress due to torque.To improve the seismic performance of cabinets,the necessary measures need to be taken to reduce the cabinet deformation and collisions between batteries and cabinets.It is recommended to install battery cabinets with large mass and high center of gravity in full welding approach to reduce the impact of geometric deformation on the seismic performance of battery cabinets.

Electrical Design & Discussion

Optimal Design Method for Opening Spring of Vacuum Circuit Breaker Spring Operating Mechanism

LI Yanyan, ZHANG Jie, WANG Junwei

2024, 0(9):  29-33.  doi:10.16628/j.cnki.2095-8188.2024.09.005

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In order to solve the problem that the opening spring can’t be maintained and the opening speed is too large or too small due to the mismatch between the output and load characteristics of the opering spring when designing the opening spring of the operating mechanism, an optimization design method for the opening spring is proposed.Firstly, the torque and power during the opening process are calculated, and then the opening speed of each shift point is calculated according to the function principle.Finally, according to the speed and energy requirements and other factors, the opening spring is optimized.The optimized opening spring can make the output characteristics and load characteristics match reasonably during the opening process, ensure the reliable opening of the mechanism, and obtain the opening speed that meets the requirements.The feasibility of the optimization method is proved by theoretical calculation and experimental verification, which provides a useful guidance for the optimal design of the opening spring of the vacuum circuit breaker spring operating mechanism.

Fault Analysis and Optimization Design of Key Shaft for Operating Mechanism of Molded Case Circuit Breaker

XIANG Xiaoqing

2024, 0(9):  34-37.  doi:10.16628/j.cnki.2095-8188.2024.09.006

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Based on the physical prototype of molded case circuit breaker, the bending failure of the buckle shaft in the operating mechanism is analyzed during the mechanical life test, the theoretical calculation process of the buckle shaft is given, the cause of the buckle shaft bending failure is explained, and the two commonly used materials are screened and the optimal solution is given.The finite element model of the buckle shaft is established by Ansys Workbench software, the bending fault of the buckle shaft is restored by static structure analysis, and the strength of the optimized buckle shaft is checked.The combination of theoretical calculation and simulation analysis can provide a reference for the independent design and optimization of the key shaft of the operating mechanism and other components of the molded case circuit breaker.

A Bidirectional Bridgeless Flyback Tri-Port LED Driver with Active Clamping

HUANG Shuchen, LIN Weiming, ZHENG Yong, LIN Zhongyin

2024, 0(9):  38-50.  doi:10.16628/j.cnki.2095-8188.2024.09.007

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In order to apply LED lighting in photovoltaic power generation, other new energy generation, grid power supply, and multi-energy joint power supply scenarios, an active clamping inhibit leakage voltage spike snubber multi-port bidirectional driver structure is proposed, which can realize the grid-side power supply and photovoltaic power and other multi-energy power supply to adapt to a variety of lighting scenarios. The operating principle and operating process of the proposed circuit are analyzed in detail.The steady-state operating characteristics of the proposed circuit in various operating modes are analyzed.The key parameters of the circuit are designed. Finally,the computer simulation are carried out with an AC grid input voltage range of 185~265 VAC, an output current of 2 A and an output power of 96 W is set up. In the AC grid power supply operating mode, the power factor is obtained to be 0.998, the THD is obtained to be 4.7%, and the efficiency of the proposed circuit is obtained to be up to 87.2% at full load. The computer simulation results and experimental results have been obtained to verify the effectiveness of the proposed circuit and its active clamping method.

Design of a Thick Film Hybrid Integrated Spaceborne Secondary Power Supply

ZHENG Dong, DONG Xiaowei, GAO Donghui, HUANG Yuwei

2024, 0(9):  51-59.  doi:10.16628/j.cnki.2095-8188.2024.09.008

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A design method for the secondary power supply is proposed to meet the demand of high-power, high-efficiency, and miniaturized secondary power supplies for spaceborne radar systems.The circuit design and the process design schemes are introduced in detail.The various functions such as power conversion, surge suppression, EMI filtering, and protection are integrated in the power module.The process is based on thick-film hybrid integrated microassembly technology and the structure adopts a double-layer assembly structure design.The simulation analysis is carried out.Finally, a prototype is developed and tested.Test results are confirmed that compared to traditional power supplies, the designed secondary power supply has reduced volume by 85% and weight by 74%,which can offer a miniaturized and lightweight solution for spaceborne radar system’s secondary power supply needs.

Detection & Experiment

Experimental Study and Analysis on Breaking Test Method 1 of 40.5 kV/31.5 kA Current Limiting Fuses

PENG Jianfei, HU Dingyin, YI Pengfei

2024, 0(9):  60-63.  doi:10.16628/j.cnki.2095-8188.2024.09.009

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The single-phase test of a 40.5 kV/31.5 kA current limiting fuse (Method 1) is focused, where the fuse body explodes and the product experiences relative ground arcing.Based on the test parameters and the selected test circuit, the experimental analysis is conducted,and the impact of this test circuit on this single-phase test is proposed.The simulation analysis is conducted on the phenomenon of relative ground arc pulling.Finally,the optimization measures for this test circuit is provided.

Virtual Resistance Adaptive Method for Active Dampers Based on Fourier Transform

WU Dong, WANG Lei, SHENG Congbing, QIN Shuang, KANG Zhaonian

2024, 0(9):  64-70.  doi:10.16628/j.cnki.2095-8188.2024.09.010

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In order to solve the problem of large working capacity and high loss of active damper caused by the fixed virtual resistance value,the virtual resistance adaptive control strategy based on Fourier transform is proposed.Taking the grid-connected inverter with the resonance stability as the object,the reason of resonance in the inverter is analyzed,the stability of the system is corrected by designing the virtual resistance of the active damper.Finally,the magnitude of the resonance voltage component is extracted at the common coupling point according to the Fourier transform,and the value of the virtual resistance dynamically is adjusted,so as to make the active damper work at a lower capacity and provide the suitable damping for the system at the same time.Simulation shows that the proposed strategy can effectively suppress the resonance of the voltage at the point of common coupling,effectively reduce the working capacity of the active damper at the same time,and improve the ability of the active damper to solve the resonance problem.

Research on an Online Measurement and Testing Technology of Charging Pile for Electric Vehicle

ZUO Yong, ZONG Haile, RONG Guocan, LIN Naiqi, ZHANG Xingchao

2024, 0(9):  71-76.  doi:10.16628/j.cnki.2095-8188.2024.09.011

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In order to solve the problems of large workload, high verification frequency and lag in the manual verification of electric vehicle charging pile, the online measurement and testing system of electric vehicle charging pile is designed.The verification system consists of a charging pile detection module, an online verification supervision platform and a charging service operation management platform.The online detection module is installed in the charging pile, and the uplink is connected with the charging service operation management platform and the online verification master station.The downlink is connected with the metering module in the charging pile.At the same time, 4G Internet of things communication module is used to communicate and transmit data with the charging service operation management platform and the main station.The system can realize the normal verification of the large-scale charging pile, and find the abnormal measurement or charging of the charging pile in time, which solves the problem of lag of the traditional verification method.

Standard Research & Analysis

Health Management Technology and Standardization for Low Voltage Circuit Breakers

CHEN Xueqin, CHEN Zhengxin

2024, 0(9):  77-80.  doi:10.16628/j.cnki.2095-8188.2024.09.012

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The concept of health management is introduced,and the key technologies of low voltage circuit breaker health management is analyzed.The technical requirements and functional applications of circuit breaker health management are explored and studied at a deeper level to develop the corresponding low voltage circuit breaker health management standard,which can speed up the digitalization process of traditional electrical equipment, and create a sustainable and high quality development ecology of the industry.