Table of Content

30 December 2023, Volume 0 Issue 12

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Research & Analysis

Research on Joint Diagnosis of Partial Discharge Pulse Current and Leakage Current in Transformer Core Ground Line

YANG Ming, HOU Chunguang, GAO Youhua

2023, 0(12):  1-7.  doi:10.16628/j.cnki.2095-8188.2023.12.001

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Partial discharge (PD) detection is an important and effective method to evaluate the insulation status of electrical equipment. The high frequency pulse current will be generated in the ground line of transformer core when PD occurs, and the leakage current of transformer core can also reflect the multi-point ground fault of transformer core. A joint diagnosis method for detecting partial discharge fault of transformer and multi-point ground fault of iron core by using ultra-bandwidth high frequency current transformer is proposed. A partial discharge detection system is built to simulate the partial discharge of the transformer, and two signal pre-processing circuits are designed to extract the high-frequency current and leakage current information of the transformer core ground line respectively. Harmonic analysis is used to extract the fundamental amplitude of the leakage current, and BP neural network based on genetic algorithm is used to classify the fault current of the transformer partial discharge. The accuracy of the model is verified.

AGV Anti-Misalignment Wireless Power Transfer System Based on DQD Magnetic Coupler

SU Tianzhang, LIN Jinhui, MAO Xingkui, Zhang Yiming

2023, 0(12):  8-12.  doi:10.16628/j.cnki.2095-8188.2023.12.002

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A wireless power transfer(WPT) system based on DQD magnetic coupler is proposed for the problems of fluctuation of coupling coefficient due to coil misalignment and high cost and weight of traditional magnetic coupler in the process of WPT system of automatic guided vehicles (AGV). Firstly, the DQD magnetic coupler is modeled and analyzed by Maxwell finite element simulation software. It is verified that the proposed magnetic core layer structure can save the amount of cores to a large extent while retaining the original coupling coefficient. Secondly, the output characteristics of the WPT system based on the LCC-S compensation topology are derived. The necessity of optimizing the anti-misalignment performance is verified. Finally, an experimental platform is built. The measured and simulated results are basically consistent, which can prove that the DQD magnetic coupler has good anti-divergence performance and verifie the feasibility of the proposed scheme.

Research on a Combination LED Driver Circuit and Its BPSK Communication Modulation Strategy

JING Huafeng, LIN Weiming

2023, 0(12):  13-21.  doi:10.16628/j.cnki.2095-8188.2023.12.003

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Based on the combination of boost Boost circuit and improved synchronous rectification buck Cuk circuit, a DC/DC combined LED driver circuit for visible light communication is proposed. The high conversion efficiency is achieved by the boost Boost circuit with lower switching frequency processes most of the power (LED lighting power). The improved synchronous rectification buck Cuk circuit with high switching frequency modulates communication signals to achieve high communication performance. A detailed analysis of the working principle and process of the proposed circuit is conducted. A binary phase shift keying modulation strategy is adopted for the design. Finally, through computer simulation analysis and experiments, the feasibility and effectiveness of the proposed combination circuit and BPSK communication modulation strategy are verified.

Research on Simplified Variable On-time Control of Critical Boost-PFC Circuit

XIAO Zhantao, WAN Lufeng, CHEN Xinwei, XIAO Jian

2023, 0(12):  22-31.  doi:10.16628/j.cnki.2095-8188.2023.12.004

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Aiming at the problem of poor line characteristics of the critical Boost-PFC circuit with traditional constant on-time control for the obvious crossover distortion, three simplified variable on-time (VOT) control strategies were proposed to improve the line characteristics of the circuit. The three kinds of VOT control strategies were compared and analyzed in detail.Finally, the computer simulation and 200 W prototype experiment were carried out.The computer simulation and experimental results show that the proposed three VOT control strategies can effectively improve the grid-side characteristics of the circuit and the efficiency of the circuit.

Simulation Analysis on Thermal Stability of Medium Voltage DC Circuit Breakers Based on Workbench Sequential Coupling

HUANG Tianjing, MA Ziwen, KONG Fanliang

2023, 0(12):  32-38.  doi:10.16628/j.cnki.2095-8188.2023.12.005

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The medium voltage DC circuit breaker is an important protective device in the medium voltage DC power supply and distribution system. A sequential coupling simulation model for the thermal stability of the medium voltage DC circuit breaker is established based on the Workbench. The transient temperature rise of a certain type of medium voltage DC circuit breaker with a rated current of 6 000 A under 70 kA/250 ms short-circuit current impact is simulated and analyzed. At the same time, considering the influence of the electric force generated by short-circuit current on the radius of the conductive bridge, a calculation program for the iterative change of the radius of the conductive bridge during the current flow process is designed, which can provide a more accurate simulation basis for the design of the thermal stability ability of medium voltage DC circuit breakers.

Electrical Design & Discussion

Zero Input Current Ripple High Gain DC/DC Converter Based on Coupling Inductor

AN Jinhai, XING Xingwei, ZHANG Chang

2023, 0(12):  39-47.  doi:10.16628/j.cnki.2095-8188.2023.12.006

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A high gain DC/DC converter with zero input current ripple is proposed to address the drawbacks of low voltage gain, high switching device stress, and large input current ripple in traditional DC/DC converters. The reduction in switching device voltage stress and the increase in input output voltage gain are achieved. At the same time, without limiting the duty cycle and adding additional auxiliary circuits, coupling inductance technology is used to eliminate input current ripple and reduce the number of magnetic cores. A detailed analysis of the working principle of the converter and the implementation mechanism of zero input current ripple are provided. Finally, the correctness of the theoretical analysis is verified by constructing an experimental prototype with a rated power of 400 W.

Research on Mechanism of Stability Time of Aerospace Relays

SHI Lei, LIN Wenhai, TIAN Jiaxin, XIAO Huayu

2023, 0(12):  48-52.  doi:10.16628/j.cnki.2095-8188.2023.12.007

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A method for controlling the stability time of aerospace relays is proposed to meet with the added the testing requirements for a failure rate level of M aerospace relays contact stability time compared to the ordinary relays.The main factors affecting contact stability time are studied.The effects of test load, contact cleanliness, and other factors on contact stability time is verified by the experimental data.

Design of PI Constant Current Charging Controller for Mining Permanent Magnet Contactor

HUANG Kecheng, WANG Xianbing, PENG Jing, HOU Ziyang, PENG Jiyu

2023, 0(12):  53-59.  doi:10.16628/j.cnki.2095-8188.2023.12.008

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To improve the service life of energy storage capacitors in permanent magnet contactors and ensure the reliability of permanent magnet contactors in mines, a constant current charging control strategy for energy storage capacitors based on the proportional integral (PI) algorithm is proposed.A PI constant current charging simulation model is built using MATLAB, and an improved PI constant current charging controller simulation experimental platform based on the Buck circuit hardware structure is constructed.The simulation and experimental results show that the energy storage capacitor can achieve constant current charging under the control of the proposed improved PI controller, which meets the expected reference value for constant current charging.It has practical significance for enhancing the circuit stability, extending the service life of the energy storage capacitor, and improving the overall intelligence of the controller.

Research on Low Inductance DC Testing Technology for New Energy Vehicle Electrical Appliances

ZHANG Yan, DONG Jisheng, ZHANG Huajun, MENG Zhejian

2023, 0(12):  60-64.  doi:10.16628/j.cnki.2095-8188.2023.12.009

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In response to the characteristics of the low overall circuit inductance for the new energy vehicles using batteries as their power source, a low inductance DC testing system is developed using the supercapacitor modules as experimental adjustable power sources, IGBT series connection and synchronous drive, non-inductive resistance, PLC control, and other technologies.The system has a maximum short-circuit detection capacity of 20 kA/DC 1 500 V and can be used for various tests of new energy vehicle electrical appliances (such as DC contactors, fuses, etc.) under low inductance (time constant of 0.5ms and below) conditions.At the same time, the problem of high inherent inductance caused by long transformers and transmission lines in the DC testing system using rectification form, which can not meet the requirements of low inductance testing, has been solved.

Simulation and Experiment Research on Double Break DC Circuit Breaker

ZHANG Liang, ZHOU Liu, HU Kai

2023, 0(12):  65-70.  doi:10.16628/j.cnki.2095-8188.2023.12.010

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A fast vacuum switch in parallel with a power electronic component containing IGCT is used in the conventional current injection DC circuit breaker to achieve the task of breaking the rated current and short-circuit current of the circuit breaker. In response to the phenomenon of commutation failure caused by the natural transfer of fast vacuum switch breaking current to IGCT power electronic components during the rated current breaking process of a single break DC circuit breaker, as well as the possibility of arc reignition at the break of the fast vacuum switch under high short-circuit current breaking conditions, an improvement design method is proposed to form a double break DC circuit breaker by connecting two fast vacuum switches in series.And the boundary capability analysis on the main parameters that affect the breaking performance of two fast vacuum switches is conducted. Through simulation and experiment verification, the double break DC circuit breaker can effectively eliminate the phenomenon of commutation failure and arc reignition, which can improve the reliability of the circuit breaker and the feasibility of practical engineering applications.

Standard Research & Analysis

Study on Breaking Ability Testing Method of DC Low-Voltage Fuse Based on Comparison of GB,IEC and UL Standards

ZHAO Jing, LI Saisai, BAI Chengzong, GUO Xiangrong

2023, 0(12):  71-76.  doi:10.16628/j.cnki.2095-8188.2023.12.011

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In order to study the impact of differences between GB, IEC, and UL standards on the detection of the breaking capacity of low-voltage fuses, the applicable objects, breaking capacity limits, and breaking capacity testing methods of standards were compared. It was found that there were significant differences in small overcurrent tests. According to GB, IEC, and UL standards, small overcurrent breaking tests were conducted under different expected testing currents, switching times, and preheating methods. The results showed that the curve between the pre-arcing time of the fuse and the expected testing current basically coincided under different expected testing currents.The pre-arcing time, breaking voltage and initial voltage measured by AC or DC preheating are basically consistent.Different switching times prolong the full voltage circuit time, but not affect the arcing process and the testing results of the recovery voltage.

Application

Analysis on Short-Circuit Closing Performance of Grounding Switch in Environmental Gas Ring Network Cabinet

CHENG Junqi, LI Zheyuan, ZHOU Yin, WANG Zhi

2023, 0(12):  77-82.  doi:10.16628/j.cnki.2095-8188.2023.12.012

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According to the user's needs, the layout of the three position grounding switch and the main switch of the new environmental gas ring network cabinet in operation is different. In order to meet the requirements of the standard that the grounding switch must have the ability to meet the short circuit current, in view of the safety regulations and the national grid ring network cabinet standardization regulations, the environmental gas ring network cabinet in operation is sampled and tested. The several aspects such as the grounding switch closing current testing circuit, the testing process, the national standard requirements, the technical indicators of the test, and the factors affecting the closing ability are elaborated. The test results show that the environmental gas ring network cabinet with the lower three position grounding switch successfully passed the short circuit closing test of the grounding switch, which can provide a basis for on-site operation.