Table of Content

30 July 2022, Volume 0 Issue 7

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Research & Analysis

Experimental Study on Low Current Fusing Characteristics of Fuse for Medium Voltage Transformer Protection

ZHENG Jiaxi, WANG Guoqing, LIN Boyong, LIU Chun, LIU Xun, ZANG Chunyan

2022, 0(7):  1-6.  doi:10.16628/j.cnki.2095-8188.2022.07.001

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The fuse used to protect the medium voltage transformer is an overcurrent protection appliance for the high voltage side of distribution transformer. According to the regulations of China Southern Power Grid,if the conventional non-fusing current is less than 1.3I_n,the fuse is not allowed to melt. A large number of temperature rise characteristic tests under 1.0I_n,1.25I_n,1.4I_n,1.6I_n and 2.0I_n current are carried out with the brand-new samples of fuses for protection to medium voltage transformer from 10 manufacturers at home and abroad,and the fusing characteristics under low current are studied. It is shown that the maximum resistance of fuse-element under 0.1I_n is about 16 mΩ and the minimum is about 8.3 mΩ. The unqualified rate of the samples submitted for the inspection can reach 30%,which has important reference value for the selection,procurement and quality evaluation of the fuses for the protection of medium voltage transformers.

IPOP Double Resonant LLC Converter Based on Coupled Resonant Inductance

TIAN Jian, XU Yuzhen

2022, 0(7):  7-15.  doi:10.16628/j.cnki.2095-8188.2022.07.002

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In low-voltage and high-power occasions,the system efficiency and reliability can be improved by the parallelled multiplexers.Aiming reducing the reliability of the system and limiting the application rang of the traditional double resonant LLC converter with the searies secondary winding of the transformer,an IPOP double resonant LLC converter with the parallel secondary windings of the converter is proposed.In order to solve the current sharing problem caused by inconsistent device parameters in the IPOP double resonant LLC converter,the two-phase resonant inductance is coupled to realize the automatic current sharing of the converter output.By establishing the FHA model and simulation analysis of the converter,the current sharing error distribution characteristics are studied when the resonance parameters are asymmetric,and the comparative experiments are verified the correctness of the theoretical analysis by building a 2.16 kW prototype.

Research on Primary-Side Soft Switching of Double-Inverter MC-WPT System

YIN Yong, ZHANG Xiaofeng, WANG Chengliang, XU Qingqiang

2022, 0(7):  16-20.  doi:10.16628/j.cnki.2095-8188.2022.07.003

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For a class of high-power wireless power transmission applications,the system uses the LCC-S type compensation topology structure,which requires the multiple inverters in parallel to improve power capacity and system stability.In order to reduce the turn-on and turn-off loss of the multiple inverter modules,the conditions for the primary-side LCC resonant network to achieve soft switching are derived.By designing the primary-side resonant network with asymmetric parameters,the impedance of the system is weakly inductive.The zero-voltage turn-on and turn-off of the switch tube are realized.Simulations and experiments verify the feasibility of the proposed design scheme to realize the soft switching of dual inverter parallel system in large power range.

Research on Classification of Power Quality Disturbances Based on GAF and Transfer Learning

QIU Xing, YIN Shihong, ZHANG Zhihan, PAN Shenchen, JIANG Minfeng, YANG Jianming, ZHENG Jianyong

2022, 0(7):  21-26.  doi:10.16628/j.cnki.2095-8188.2022.07.004

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Aiming classifying the power quality disturbance (PQD),a PQD classification method based on Gramian Angular Field (GAF) and transfer learning proposed.First,GAF is used to convert one-dimensional PQD signal data into two-dimensional pictures.Then,the generated pictures are trained and classified by the improved transfer learning model AlexNet,and the PQD classification is completed.Finally,the IEEE 14 model is used to simulate different types of PQD signals,and the proposed mothod is verified.The results show that the proposed method is effective.

Quantitative Assessment Method of Wind Farm Resilience Under Extreme Wind Conditions

JING Tonghui, WANG Xiaodong, LIU Yingming, LI Shanshan

2022, 0(7):  27-35.  doi:10.16628/j.cnki.2095-8188.2022.07.005

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In the context of building a new power system with new energy as the mainstay,aiming at the problem of wind farm resilience assessment under extreme conditions,a quantitative evaluation method of wind farm resilience under extreme wind conditions based on Monte Carlo simulation is proposed.On the basis of clarifying the concept of wind farm resilience,based on multi-stage elastic polygons,the wind farm resilience quantification and evaluation index is proposed,and the method for determining the failure of each component of the wind farm is proposed by modeling the extreme wind events and wind farm states.The wind farm resilience assessment method based on the sequential Monte Carlo simulation is proposed by supplementing the degradation and restoration stage model.Finally,a example is used to evaluate four types of wind farm infrastructure and operational resilience,and the effectiveness of the proposed method is verified by analyzing the influence of physical strength and redundant equipment performance on the resilience.

Electrical Design & Discussion

Detection Device of Transformer Substation Battery Pack Based on Wireless Communication Technology

MA Yan, WU Hang, ZHOU Ya, CAO Hai, HUANG Haihong

2022, 0(7):  36-40.  doi:10.16628/j.cnki.2095-8188.2022.07.006

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In order to ensure that the battery pack provides uninterrupted power supply for the load in case of AC power failure,configuring the battery monitoring device to monitor the battery state in real time has become a conventional scheme of DC power supply system in important substations.A set of distributed battery detection device based on wireless communication for 2 V battery pack is designed.The system is composed of a monitoring unit and several test units.The device is equipped with a test unit for 3 or 4 batteries in series.The single chip microcomputer built-in analog-to-digital conversion module is used in the test unit,which can detect the corresponding battery terminal voltage in real time and configure the resistance discharge module at the same time.The monitoring unit uses wireless communication to call the test unit with station number in broadcast mode to obtain data,and sends internal resistance detection command in response to on-site manual command or remote control command.The test unit uses twi-discharge method to realize on-line detection of corresponding battery internal resistance.The experimental results show that the device can effectively measure the battery voltage and internal resistance.

Design of Integrated Self-Excited Fluxgate DC Current Sensor for Power Distribution

YUAN Yaoxin, CHEN Wei

2022, 0(7):  41-49.  doi:10.16628/j.cnki.2095-8188.2022.07.007

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Under the background of “dual carbon”,the integrated high precision current measurement of intelligent appliances is required in the power supply and distribution network.The existing equipment can not simultaneously meet the needs of accuracy,range and volume constraint at the same time.To solve the problems of easy saturation and small linear measurement range caused by the small magnetic core in the limited space,a multi-core current sensor is designed based on the self-excited fluxgate.The average excitation current model based on arctangent magnetization fitting curve is constructed.The multi-objective genetic algorithm is adopted to optimize the structure and electromagnetic parameters with the targets of volume and accuracy.On this basis,the closed-loop prototype with three magnetic cores and four windings is trial produced.Compared with LEM cab,the outer diameter of the sensor prototype is reduced by 25% on the premise of ensuring the linearity.The accuracy is better than the national standard level 0.2.The measurement range meets the requirements of circuit breaker measurement.

Image Recognition Method of High Voltage Circuit Breaker Indicator Light Based on Feature Matching

LIU Yan, LI Chang

2022, 0(7):  50-55.  doi:10.16628/j.cnki.2095-8188.2022.07.008

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The color feature algorithm of video image is used to recognize the on and off state indicator light of circuit breaker.A typical image is divided into regions.According to the characteristics of indicator light on and off image,a 6 values gray level construction method is used to construct the image color features.Through feature collection and training of historical images in various environments,the expert knowledge base of online recognition is obtained Finally,the online video images are analyzed in real time according to the feature expert knowledge base,and the alarm is issued by comparing the preset values..Using the real-time picture data of railway traction substation in operation,the image recognition of circuit breaker on and off state is carried out in the example.The results show that the proposed method is feasible in the on-line image recognition and has certain practical value.

Low Current Ripple Electrolytic Power Supply and Its Control Method

WANG Tong, ZHOU Jie, XIAO Huagen, SU Minchao, WU Yihu

2022, 0(7):  56-61.  doi:10.16628/j.cnki.2095-8188.2022.07.009

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Aiming at the demand of low current ripple electrolytic power supply in electrolytic copper foil industry,a topology and control method of low current ripple electrolytic power supply are proposed.The electrolytic power supply is composed of a PWM rectifier and a DC/DC converter in cascade,where the DC/DC converter is composed of a plurality of DC/DC conversion modules in parallel,and each DC/DC conversion module is composed of a half bridge high-frequency inverter and a full wave uncontrollable rectifier circuit.By controlling the output voltage of the high-frequency inverter in each DC/DC conversion module to stagger the equal phase angle,the low-frequency harmonic components of the output voltage of multiple DC/DC conversion modules are mutually offset,so as to reduce the output current ripple of the electrolytic power supply.Finally,the effectiveness of the proposed topology and its control method is verified by the experimental results.

Simulation Technology Application

Design of Active-Clamp Flyback Dual Output DC/DC Converter with Synchronous Rectification

JIN Yang, ZHANG Sen, CHENG Ming

2022, 0(7):  62-66.  doi:10.16628/j.cnki.2095-8188.2022.07.010

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In order to reduce the volume of dual output DC/DC converter,the flyback topology with simple structure is adopted,and the active clamping technology and synchronous rectification technology are introduced to significantly improve the voltage stress and conversion efficiency.Based on the principle of low-side clamp technology,the zero-voltage turn on of primary power device and zero-current turn off of the synchronous rectifier device are realized.Meanwhile,based on the principle of self-driven synchronous rectification technology,a voltage type self-driven synchronous rectification circuit suitable for dual output is proposed.A ±5 V/6 A dual output DC/DC converter is realized by the circuit simulation and prototype verification.It has the advantages of high conversion efficiency,large output current,small volume and so on,which can meet the application environment of high reliable power supply.

Matching Calculation Analysis and Application of Medium Voltage Vacuum Circuit Breaker Operating Mechanism Counterforce Characteristic

ZHOU Qiang

2022, 0(7):  67-72.  doi:10.16628/j.cnki.2095-8188.2022.07.011

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The operating mechanism is the power output source of the vacuum circuit breaker,which provides the necessary energy of short-circuit breaking and closing.The counterforce characteristic matching curve of the operating mechanism determines whether the circuit breaker can close smoothly and the mechanical characteristic parameters can meet the design requirements during the closing process.From the perspective of statics mechanics,one calculation method that solves the relationship between the dynamic torque and resistance torque of the main shaft during closing process at any time is introduced,and the influence of the energy storage spring final force on the counterforce characteristic matching curve is studied,which has a great engineering significance for the optimal design of parameter variables such as energy storage spring,break-brake spring and contact spring in the operating mechanism of circuit breaker.

Research on Electrothermal Coupling Simulation Method of Single-Phase IOT Smart Meter Metering Unit Based on Simulink and Ansys Icepak

YUAN Ruiming, LI Wenwen, PANG Fukuan, GUO Jiao, WANG Chen

2022, 0(7):  73-79.  doi:10.16628/j.cnki.2095-8188.2022.07.012

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IOT smart meter is a complex electronic system,the measurement accuracy will be affected by temperature,load,component parameters,etc.There are complex electrical and thermal effects in the measurement unit of the IOT smart meter,which can affect the working state of the electronic system,and the simple thermal model cannot meet the accuracy requirements.A mainstream single-phase IOT smart meter is taken as an example.First,analyzing the metering principle.Then,using Simulink and Ansys Icepak to construct the electrical and thermal simulation model of the metering unit of the meter considering the influence of temperature.Finally,obtaining the temperature field of the smart meter under different ambient temperatures by using the electrothermal indirect coupling simulation method.The experiments show that the accuracy of electrothermal coupling simulation is higher than that of single thermal simulation,and the maximum error between the simulation data and the measured data is 2.2%,which is good.

Application of Multi-Rigid Body and Rigid-Flexible Coupling Analysis Based on Finite Element Simulation Software in Air Circuit Breaker

XING Leilei

2022, 0(7):  80-85.  doi:10.16628/j.cnki.2095-8188.2022.07.013

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Based on the multi-rigid body dynamic model of the circuit breaker contact system and mechanism system established by Creo and ADAMS,the reason for the bending deformation of the energy storage shaft in the actual experiment of the circuit breaker is analyzed by Ansys.Based on Hypermesh,Ansys and ADAMS,a rigid-flexible coupling model was established to make the lower link flexible and the contact system and other parts in the mechanism system rigid.The reasons for the fracture and failure of the lower link were analyzed through simulation calculation.Finally,through the calculation of two cases,it is indirectly proved that the results of multi-rigid calculation and rigid-flexible coupling analysis calculation by software have certain reference value,and also provide a basis for the solution of other similar problems in the subsequent product development process.

Standard Research & Analysis

Standard Difference Analysis and Reseasrch of Low-Voltage Reactive Power Compensation Assemblies (GB/T 15576—2020) and Low Voltage Hybrid Dynamic Reactive Power Compensation Assemblies (T/CPSS 1001—2019)

LIU Peng

2022, 0(7):  86-90.  doi:10.16628/j.cnki.2095-8188.2022.07.014

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The two standards Low-voltage Reactive Power Compensation Assemblies (GB/T 15576—2020) and Low Voltage Hybrid Dynamic Reactive Power Compensation Assemblies (T/CPSS 1001—2019) was successively issued,which have the targeted technical requirements and detection provisions for the low voltage switchgear assembly reactive power compensation devices.The main differences of the two standards are studied and analyzed from the aspects of the standard application scope,terms and definitions,device classification,service conditions,basic protection,control and protection functions,performance test,electromagnetic compatibility test,ambient temperature performance test,etc.,which can provide the reference for relevant personnel.

Application

Construction and Application of Unified Information Management Platform for Low Voltage Apparatus Digital Workshop Based on Industrial Internet Architecture

GAO Xiaotian, HU Min, GUAN Yongan

2022, 0(7):  91-95.  doi:10.16628/j.cnki.2095-8188.2022.07.015

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In the process of the development of intelligent manufacturing and industrial Internet technology in the low-voltage electrical apparatus industry,there is rapidly growing demand for building a unified information management platform for digital workshops to realize information interconnection,intelligent analysis and unified information display.From the analysis of industry needs,a unified information management platform architecture for the digital workshop of low-voltage electrical apparatus based on the industrial Internet is designed.Furtherly,the development ideas of specific functional modules such as platform data acquisition,edge computing,quality traceability,equipment management and workshop unified information management are put forward.Based on the developed platform,the demonstration application in industrial enterprises is introduced.Finally,the future direction of the unified information management platform for low voltage apparatus is discussed.