LOW VOLTAGE APPARATUS

Early Fault Diagnosis of Permanent Magnet Synchronous Wind Turbine Rotor Eccentricity Based on CNN-LSTM

XIE Tongtong, LIU Yingming, WANG Xiaodong, GAO Xing

2024, 0(3): 1-6. doi:10.16628/j.cnki.2095-8188.2024.03.001

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Research is conducted on the characteristics and diagnostic methods of early dynamic eccentricity and early static eccentricity faults in the rotor of permanent magnet synchronous wind turbines.The early dynamic eccentricity and early static eccentricity models for permanent magnet synchronous wind turbines are established using Ansys,and a fault diagnosis and classification method based on CNN-LSTM is proposed.By analyzing the three-phase current and Welch power spectrum data of the stator of a permanent magnet synchronous wind turbine generator,the generator’s current status can be judged whether it is normal dynamic eccentricity trend or normal static eccentricity trend.Then,the different fault levels are classified using no-load electromotive force.Finally,the fault diagnosis and classification tasks in the neural network model are completed.The proposed method greatly reduces equipment maintenance costs and can accurately and quickly identify early rotor eccentricity faults.

A VCFF Control Strategy of BCM Boost PFC Circuit

LIU Guangqing, LIN Weiming

2024, 0(3): 7-14. doi:10.16628/j.cnki.2095-8188.2024.03.002

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The control strategy of constant on time (COT) is usually used in Boost power factor correction (PFC) circuits working in boundary conduction mode.The change of switching frequency in this control strategy is related to the input voltage,output power and the inductor.The conversion efficiency of the circuit will be affected by too high switching frequency under light load.Aiming at the above problems,a control strategy of valley count frequency flyback (VCFF) is proposed.By detecting the valley count of the MOS transistor voltage,the circuit works in discontinuous conduction mode during light load to reduce the switching frequency and improve light load efficiency.A prototype experiment is made.The experimental results show that compared with the COT control strategy,the proposed control strategy can effectively improve the light load efficiency.Under the input voltage of 220 Vrms,the 10%~50% load efficiency can be reached up to above 0.96.

A Guardian DC Power Supply System Based on Battery Tap Grouping and Its Control Strategy

CHENG Yujie, YANG Shiqi, DING Yuan, LI Xinyuan, ZHANG Zhenyuan, CHENG Xingbang

2024, 0(3): 15-20. doi:10.16628/j.cnki.2095-8188.2024.03.003

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The traditional DC power supply system adopts a series connection structure of batteries,which has problems such as low reliability,high energy consumption of manual battery capacity,and safety hazards.A guardian DC power supply system based on battery tap grouping and its control strategy are proposed without changing the traditional DC system structure.By grouping and boosting parallel batteries to achieve redundant power supply to the bus,the problem of bus voltage loss caused by single battery failure in the battery pack is solved.The reliability of DC bus power supply is improved.At the same time,a protective DC power supply system’s automatic capacity allocation strategy is proposed to reduce energy loss during manual capacity allocation and improve the maintenance efficiency of DC power supply equipment.

Modeling and Reliability Evaluation of Multivariate Wiener Degradation Process for Relays Based on Truncated Normal Distribution

GUAN Xin, LIU Xi, MA Lin, LIU Mai, ZUO Tianming

2024, 0(3): 21-29. doi:10.16628/j.cnki.2095-8188.2024.03.004

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The reliability evaluation of relays is carried out on the basis of the multi-performance degradation model based on the degradation data of multi-performance parameters of relays.Several relay parameters are selected.An improved multivariate Wiener degradation model based on truncated normal distribution is established considering the actual statistical characteristics of the model parameters boundedness.Aiming at the established performance degradation model,a multi-stage model parameter estimation method is proposed.Taking reliability as the evaluation index of relay reliability,a reliability approximation calculation method based on Monte Carlo simulation is proposed.The accuracy and effectiveness of the method are verified by practical cases.

Storage Life Prediction Method of Aerospace Electromagnetic Relay with Improved RBF Neural Network Based on Snake Algorithm Optimization

LI Jiuxin, WANG Zhaobin, ZHU Jiamiao

2024, 0(3): 30-35. doi:10.16628/j.cnki.2095-8188.2024.03.005

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Aiming at the prediction and prediction accuracy of contact resistance of aerospace electromagnetic relays,a radial basis function (BRF) neural network model based on snake optimization (SO) algorithm is proposed.On the basis of the traditional RBF model,the SO algorithm is used to optimize the weight parameters so as to better predict the contact resistance value of the relay.The constructed SO-RBF prediction model is compared with RBF model.The models are used to predict the change trend of contact resistance.The comparison and analysis of the prediction results show that the proposed model has high prediction accuracy.

Research on Contactor with Controllable Contact Gap

CHEN Weibin, LIU Xiangjun

2024, 0(3): 36-41. doi:10.16628/j.cnki.2095-8188.2024.03.006

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In order to improve the breaking current capacity of the traditional electromagnetic contactor and solve the disadvantages of high closing power consumption, large impact force of the moving iron core and serious wear of the iron core under large contact gap, a contactor with controllable contact gap is designed. Through structural improvement, the gap of the contact that can be opened at the structural level of the traditional AC contactor is increased. The control circuit based on the single-chip microcomputer is used to identify the breaking current, and the pulse current with different width is applied to the excitation coil during the breaking process, so that the contactor has different gap under different breaking current. After the breaking, the contact returns to the balance position of small gap. Through experiments, it is verified that the designed contactor has the function of controllable contact gap.

Design and Implementation of a Combined IoT Circuit Breaker Controller

LIANG Shanguang, ZHAO Jie, YIN Senlin

2024, 0(3): 42-46. doi:10.16628/j.cnki.2095-8188.2024.03.007

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In order to achieve the reusability of the internal controller of IoT circuit breakers for different phase numbers of circuit breakers,a combination design of circuit breakers,power supplies and gateways is adopted in hardware,and a scheme different from traditional measurement chips is adopted in software.A design and implementation method of the circuit breakers internal controller collecting voltage and current values directly through ADC combined with software algorithms is proposed,and a method for automatically allocating circuit breaker addresses is also proposed.And the accuracy of electrical quantity collection is tested through experiments.The proposed method solves the problem of single-phase circuit breakers requiring the introduction of a neutral line and circuit breakers with different numbers of phases relying on different types of acquisition chips,which greatly reduces the production costs and provides the convenience for normalized management of production materials.

Design on Operating Mechanism Key Parameters of Moulded Case Circuit Breaker

LI Peng

2024, 0(3): 47-52. doi:10.16628/j.cnki.2095-8188.2024.03.008

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On the basis of briefly describing the action principle of the operating mechanism of the moulded case circuit breaker (MCCB),a certain model of double break point MCCB is taken as the design and research object.Using ADAMS analysis software,the important parameters of the operating mechanism,such as the three elements of the contact,the opening and closing speed of the contact,the opening and closing force of the mechanism,the opening and closing stroke,and the opening and closing time,are calculated.The simulation parameters have minimal error compared to the measured parameters of the prototype.The allowance between the simulated parameters and the measured parameters of the prototype is very small.A design method of the operating mechanism key parameters is provided.

Dynamic Voltage Restorer Based on Feedforward Active Disturbance Rejection Control

SHAO Shuai, HUANG Zai, YANG Shouping, LU Min

2024, 0(3): 53-59. doi:10.16628/j.cnki.2095-8188.2024.03.009

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A feedforward compensation based active disturbance rejection control (FC-ADRC) strategy is proposed to address the contradiction between compensating speed and compensating overshoot in the traditional proportional integral (PI) control for dynamic voltage restorer (DVR).By improving the compensation overshoot problem of traditional PI control through ADRC strategy,and introducing the voltage and current of LC filter as feedforward to compensate the DVR controller,the fast voltage compensation is achieved for user side voltage sag to ensure the safety and stability of user side voltage.The simulation experiment results show that the proposed strategy maintains the high dynamic responsiveness of the DVR device while ensuring its adaptability to uncertain disturbances.

Experimental Investigation of Mechanical Wear Failure Mechanism for Connectors

HAN Yicheng, MENG Yuan, ZHANG Chao, REN Wanbin

2024, 0(3): 60-65. doi:10.16628/j.cnki.2095-8188.2024.03.010

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Mechanical wear of connectors is the main reason for the deterioration of electrical contact properties.The contact resistance and insertion force waveforms of connector are obtained by carrying out the mechanical insertion and withdrawal experiment.The degradation trends of static contact resistance and insertion force are analyzed,and the morphologies of failed pin samples are observed.Finally,the possible failure mechanisms of mechanical wear of connectors are presented.The obtained conclusions can provide a guidance for improving the reliability and lifetime of connectors.

Research on Safe Grounding Protection for Small Resistance Grounding System Considering Distributed Generation

WANG Chengjie

2024, 0(3): 66-70. doi:10.16628/j.cnki.2095-8188.2024.03.011

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Excessive residual voltage and step voltage in the case of single-phase "false power supply" of the neutral point grounding system with small resistance may pose a threat to the personal safety of operators,especially in the trend of large-scale connection of distributed generation supplies.Firstly,the grounding mode of grounding electrode and related soil characteristics are analyzed from the safety basis of grounding measures.The corresponding typical soil grounding resistance calculation method is provided.Secondly,based on PSCAD/EMTDC and Anysy software,the operating grounding model of small resistance grounding system with distributed power supply is built to analyze the problems of residual voltage and excessive step voltage.Finally,combined with the actual field verification,the effective grounding safety measures for maintenance operation are put forward to provide useful reference for relevant departments.

Application of Grey Markov Chain in Statistics Low Voltage Photovoltaic Energy Abandonment Statistics

ZHAO Zekun

2024, 0(3): 71-78. doi:10.16628/j.cnki.2095-8188.2024.03.012

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The abandoned power of low voltage distributed photovoltaics,as an important criterion for regional division and energy storage capacity configuration,has long been unable to be accurately calculated.Starting with the source network load storage system,a low-voltage distributed photovoltaic curtailment statistical model is established based on grey Markov chain.The dual scenario of “weather+time” is used to construct a state transition matrix to statistically analyze the low voltage distributed photovoltaic energy abandonment.The test results show that the proposed method can accurately obtain low voltage distributed photovoltaic energy abandonment data and control the maximum error within 5%,which has certain promotional value.

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