Table of Content

30 November 2023, Volume 0 Issue 11

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Research & Analysis

Study on Failure Mechanism Consistency Identification of Hermetically Sealed Electromagnetic Relay

YANG Xinyu, YOU Jiaxin, FU Rao, CHEN Leyu, ZENG Yuhan

2023, 0(11):  1-7.  doi:10.16628/j.cnki.2095-8188.2023.11.001

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Hermetically sealed electromagnetic relay (HSER) used in aviation and aerospace have high requirements for long-term on-load reliability.Accelerated degradation test is usually used to predict reliable life.In the multi-stress accelerated degradation test, the failure mechanism of HSER must be consistent, otherwise the product life prediction will have a large deviation.Therefore, the study on the failure mechanism consistency of accelerated degradation test is of great significance to improve the accuracy of reliable life prediction of HSER. Firstly, based on the principle of likelihood ratio detection, a consistency criterion is proposed to design an accelerated degradation test for a typical HSER.The test data is analyzed, and the consistency is checked by the criterion.After obtaining a consistency conclusion, the destructive physical experiments are carried out to analyze the degradation of the permanent magnet and spring.The effectiveness of the proposed criterion is verified.

Hum Fault Feature Extraction of AC Contactor Based on Parameter Optimization MCKD Algorithm

WAN Zuchen, BAO Guanghai

2023, 0(11):  8-16.  doi:10.16628/j.cnki.2095-8188.2023.11.002

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The defective products of AC contactor emit abnormal electro-magnetic noise after the coil is energized, which exceeds the specified noise value.According to the characteristics of AC contactor sound signal, a method combining maximum correlation kurtosis deconvolution (MCKD) algorithm and envelope spectrum analysis is proposed to extract the fault frequency and realize the abnormal vibration noise fault diagnosis of AC contactor.Firstly, the collected original signal is filtered by a band-pass filter to reduce noise interference.Then, the optimal MCKD parameters are searched by the particle swarm optimization algorithm.The signal is deconvolved to enhance the periodic pulse in the signal.The signal processed by the MCKD algorithm is used to obtain the envelope spectrum through Hilbert transform, and the fault frequency amplitude factor is used as the criterion to determine whether the AC contactors is faulty.The actual test of AC contactor shows that the method can effectively diagnose the abnormal noise of AC contactor.

Temperature Field Simulation of Automobile Relay Based on Fluid-Solid Coupling Method

WANG Qiya

2023, 0(11):  17-22.  doi:10.16628/j.cnki.2095-8188.2023.11.003

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The temperature rise to a certain extent restricts the miniaturization and lightweight development of automobile relays.It is particularly important to analyze the temperature field of automobile relays to improve their heat resistance. The computational fluid dynamics (CFD) simulation tool based on heat conduction differential equations, fluid motion control equations, and radiation heat transfer equations is used to propose a temperature field simulation method for automobile relays based on fluid structure coupling. Using the proposed method the temperature field distribution of a certain automobile relay under different environmental temperatures and load current levels are obtained. The proportion of heat dissipation through conduction, convection, and radiation is calculated. the heat dissipation law of the relay and coil under different environmental temperatures and load current levels is analyzed, which can lay a foundation for the subsequent thermal design and temperature rise optimization of automobile relays.

Analysis on Methods for Suppressing Turn off Peak Voltage of Diode Clamped Three level Converter

SHANG Yang, WANG Yongsheng, WEI Chao, HUANG Haihong

2023, 0(11):  23-27.  doi:10.16628/j.cnki.2095-8188.2023.11.004

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The causes of the turn off peak voltage of power devices in diode clamped three-level converters is analyzed.The various methods of suppressing the turn off peak voltage in engineering is discussed.Then,the matters needing attention in the use of commonly used peak voltage absorbing circuits is emphatically analyzed.The analysis results show that when the traditional RCD voltage peak absorption circuit is applied to three-level circuits,there is a problem of generated instantaneous short circuit currents if the dead time is insufficient during state transition,which poses a threat to the power circuit.Therefore,it is more appropriate to use a simplified RC absorption circuit.Finally,the above analysis is verified by simulation.

Multi Criterion Fusion Method for Small Current Grounding Fault Line Selection Based on CNN

TANG Liangxing, LI Hongjiang, LIU Xin, ZHOU Tingdong, LI Panpan

2023, 0(11):  28-34.  doi:10.16628/j.cnki.2095-8188.2023.11.005

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Aiming at the problems of difficult fault line selection and slow detection for the small and medium current grounded systems in distribution networks,a multi criterion fusion method for line selection of small current single-phase ground fault based on convolutional neural networks (CNN),Fourier transform and wavelet packet decomposition is proposed.CNN is applied to the problem of line selection for small current single-phase ground fault.Some components of the zero-sequence current of each line after processing are taken as input, and the fault line is taken as output.After a large amount of data training, the mathematical model of the fault line is obtained.When the new fault data is input into the model,the fault lines can be selected based on the mapping relationship.Finally, the feasibility of the proposed method is verified by the simulation using MATLAB/Simulink.

Research on Profit Optimization of Park Micro-Grid Based on Probabilistic Income Analysis Algorithm

LI Yonggang

2023, 0(11):  35-40.  doi:10.16628/j.cnki.2095-8188.2023.11.006

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In view of the large initial investment of park micro-grid and the uncertainty of distributed power generation,in order to fully explore and quantitatively evaluate the economic benefits of micro-grid operation,a micro-grid economic operation evaluation method based on probabilistic income analysis algorithm is proposed.In this algorithm,the uncertainty of micro-grid investment income is quantified from the perspective of income probability distribution,the resource uncertainty and prediction uncertainty are fully considered,the uncertainty models of load and photovoltaic output are established,and a large number of random scenarios are generated.By using Monte Carlo method to analyze the micro-grid monthly income,the corresponding income probability distribution curve is generated to realize the quantification of micro-grid uncertain income.The calculation results show that the method can compare the benefits of different micro-grid configuration parameters, and provide a scientific basis for the investment decision of park micro-grid.

Electrical Design & Discussion

High-Efficiency Totem Pole PFC Circuit Design Based on GaN Devices

ZHENG Runmin, LI Tang, MAO Xingkui

2023, 0(11):  41-47.  doi:10.16628/j.cnki.2095-8188.2023.11.007

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GaN devices are widely used in totem-pole bridgeless PFC circuits due to their excellent switching performance.In the inductor current critical continuous mode (CRM), Totem-Pole bridgeless PFC can achieve soft switching of the switching tube across the full input voltage range through the reasonable control.In view of the problem of complex control timing for the control mode based on the traditional current zero-crossing detection (ZCD) circuit, a soft switching control strategy based on the current state detection circuit is proposed to reduce the complexity of control.The design pressure of the EMI filter is reduced by adopting an interleaved parallel structure, and the power inductances of the two-phase circuit are integrated by using decoupling magnetic integration technology.Finally, a 3 000 W GaN-based interleaved bridgeless totem-pole PFC rectifier is built.The effectiveness of the proposed circuit design scheme is verified by experiments.

Design Method of a Medical Equipment Non-Contact Voltage Regulating Power Supply

LIU Liwei, WANG Xiaoyan, MA Benxu, WANG Yan

2023, 0(11):  48-52.  doi:10.16628/j.cnki.2095-8188.2023.11.008

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A non-contact voltage regulating and stabilizing power supply for medical equipment without the need for the conductive slip rings is designed to address the issue of wear and tear on the rotating side of medical equipment that requires direct current power supply.By utilizing the electrical isolation characteristics and voltage gain characteristics of LLC, a circuit with complete isolation of the primary and secondary sides and relative rotation is designed and implemented.Through experiments, the non-contact voltage regulation and stabilization is achieved, which can provide a feasible approach for the power supply of this type of equipment.

Research on Improving Short Circuit Breaking Capacity of 125 A Miniature MCCB

HUANG Yinfang, JIANG Guping

2023, 0(11):  53-58.  doi:10.16628/j.cnki.2095-8188.2023.11.009

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Molded case circuit breakers (MCCB) below 125 A are main force in the field of MCCBs.The main way to integrate and improve them is to elevate 63 A and 100 A products to 125 A with short circuit breaking being the main difficulty.It is possible to preliminarily increase its breaking capacity through gas producing materials.Quantified data analysis can be conducted on the condition of the arc extinguishing chamber’s grid segments through the measurement and analysis of grid voltage.The simulation of electromagnetic force is used to optimize the magnetic field of the contact part.By improving the design, the new 125A product can replace the original product and meet the performance requirements while reducing the cost of the main product.

Distributed Generation and Grid-Connection Technology

Optimal Dispatch of Regional Integrated Energy System Considering Soil Heat Emission Balance

JIANG Tao, RAN Fengxu, ZHOU Huijuan, ZHANG Qimeng, ZHANG Jinsong, ZHOU Weiran

2023, 0(11):  59-66.  doi:10.16628/j.cnki.2095-8188.2023.11.010

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In order to solve the problem of soil heat imbalance caused by the uneven operation time of ground source heat pump in winter and summer, an optimal scheduling method of regional integrated energy system considering the balance of heat discharged from soil was proposed.First, according to the operating characteristics of ground source heat pump in winter and summer, the annual heat imbalance rate of soil is calculated.Secondly, increase the use time of ground source heat pump in the cooling season to increase the heat output from the soil, so as to ensure the heat balance of ground source heat pump throughout the year.Finally, a double-layer optimization model is constructed.The upper model optimally arranges the output of ground source heat pump based on the system operating cost in winter.The lower model optimizes the output of ground source heat pump based on the system’s optimal benefit in summer, taking into account constraints such as the soil heat extraction and emission balance.Simulation examples show that the proposed method effectively solves the problem of soil thermal imbalance and improves system energy efficiency.

Research on Yaw Optimization Control Strategy of Floating Wind Farm Considering Wake Effect

LI Binbin, WANG Xiaodong, LIU Yingming, ZHU Ruonan

2023, 0(11):  67-73.  doi:10.16628/j.cnki.2095-8188.2023.11.011

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The interaction of internal wakes in wind farms affects the inflow wind speed of downstream wind turbines.To reduce the impact of wake effects on the power generation of floating wind farms, a yaw optimization control strategy of floating wind farms considering wake effects is proposed.A Gaussian curl mixed wake model is established for the specificities of the wake recovery speed changes and the impact on the wake of downstream units under yaw conditions.Considering the influence of yaw conditions on the blade displacement,the blade root load, and platform motion, a range of unit yaw angles is set as a constraint condition.Using the least squares SLSQP optimization algorithm, the optimal yaw angle and power generation of each unit in the wind farm are obtained with the maximum overall power generation as the objective function and the yaw angle as the optimization variable.The simulation results show that the proposed control strategy can effectively improve the overall power generation of the wind farm.

Application

Failure Analysis on Contact Sheet of Bridge Contacts in Circuit Breaker

FU Guangjing

2023, 0(11):  74-77.  doi:10.16628/j.cnki.2095-8188.2023.11.012

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The 60Si2Mn contact sheet of bridge contact in the circuit breaker experiences abnormal fracture under the static state.A detailed analysis is conducted on the microstructure and fracture morphology of the contact sheet using methods such as the macroscopic examination,the metallographic analysis, and the fracture analysis.A finite element model is established to simulate and analyze the stress situation of the contact sheet in using.The results show that the microstructure of the contact film is normal.The fracture morphology is mainly brittle fracture.The maximum stress value at the notch of the contact sheet is 1 818 MPa.Through the finite element analysis,the contact sheet with no notches and decreasing the length of the inner teeth by 4 mm is recommended to reduce the overall stress of the contact sheet.