Table of Content

30 May 2024, Volume 0 Issue 5

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Research & Analysis

Operation Control Key Technology Evaluation of Microgrid

LIU Xiaoming, HU Lijuan, ZHAO Fengzhan, YIXI Cuomu, WANG Wenye, LÜ Guoqing

2024, 0(5):  1-9.  doi:10.16628/j.cnki.2095-8188.2024.05.001

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The microgrid is an intelligent control system whose operation effect is closely related to its control technology.In order to realize the fine management of microgrid,the operation control key technology evaluation index system of microgrid is established from four aspects:active power control technology,voltage/reactive power regulation technology,island security technology and energy optimization management technology.And an improved variable weight evaluation method is proposed for comprehensive evaluation of microgrid operating characteristics,which can be used to solve the problem that the evaluation result can not reflect the small weight but the index value deviates from the normal value.Finally,the effectiveness of the evaluation index system and the evaluation method of the operation process of the microgrid is verified by the actual microgrid demonstration project.

Improved COT Control Strategy for CRM Boost-PFC Circuits

XIAO Jian, LIN Jianwen, ZHANG Jiakai, PAN Guangbin

2024, 0(5):  10-19.  doi:10.16628/j.cnki.2095-8188.2024.05.002

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An improved soft switching constant on-time (COT) control method is proposed to address the issues of high conduction loss caused by turn-on voltage of the Boost-PFC circuit in critical conduction mode (CRM) and poor EMI caused by high du/dt during conduction.The circuit switching transistors adaptively realize ZVS at low input voltage instantaneous value and valley conduction at high input voltage instantaneous value.The switching voltage and switching loss of the switching transistor are reduced.The du/dt of switching transistor is reduced and EMI performance of circuit is improved.The Boost-PFC circuit of CRM,the principle and working process of the proposed control method are analyzed.The influence of the proposed control method on EMI characteristics of the circuit is explored.The key parameters are designed.Finally,the simulation and experiment results show the input and output characteristics,efficiency curves and EMI curves of the prototype,which can verify the effectiveness of the proposed control method.

Research on Topology and Control Strategy for Pulsed Load Two-Stage DC-DC Power Supply

ZHANG Seng, CAO Xuan, TAN Yunfei, ZHAO Zhihong

2024, 0(5):  20-29.  doi:10.16628/j.cnki.2095-8188.2024.05.003

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In order to meet the requirements of high power density and high dynamic response performance of pulse-load DC converter,a two-stage DC converter applied to pulsed load is studied.Among them,the three-level synchronous rectifier buck converter with smaller filter inductance and higher system loop bandwidth is selected as the pre-stage converter,and the DCX (DC Transformer)-LLC resonant converter is selected as the post-stage converter,which has more advantages in dynamic response and efficiency than the closed-loop control LLC.Then,a soft-start strategy to optimize the voltage stress problem of TL(Three Level)-Buck switch is proposed,which solves the problem that the flying capacitor voltage drops to a very low level after charging in the soft-start stage.Finally,the proposed closed-loop and soft-start control strategies of two-stage DC converters are verified by simulation and experiments,and it is determined that the soft-start strategy can optimize the voltage stress of the switch during the start-up of the pre-stage TL-Buck.

Health Management Test and Research on Low Voltage Circuit Breakers

WANG Bingqing, GAO Xiaotian, ZHOU Yingzi

2024, 0(5):  30-35.  doi:10.16628/j.cnki.2095-8188.2024.05.004

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The current status of health management for low voltage circuit breakers is introduced.The correlation between contact voltage,breaking duration,breaking energy,and contact bounce with the electrical life of the contact system of molded case circuit breakers is analyzed.Through the accelerated aging test on flexible conductor,the thermal aging curve of flexible conductor is obtained by fitting the experimental data.Based on the measurement data of angular velocity and angular displacement of the main shaft on air circuit breaker,the research shows that the degree of contact wear loss can be calculated through relevant parameters,and the false closing condition can be distinguished in the meantime.The analysis of the experimental results indicates the research direction of low voltage electrical appliances health management at this stage to lay a solid foundation for the smart product and industrial internet platform design.

Research and Analysis on Data Quality Diagnosis Method Based on Multi-Source Measuring Information

XIE Lin, TAO Lei, YE Ruili, FENG Qiong, FENG Chaohan, ZHANG Zhoujie

2024, 0(5):  36-45.  doi:10.16628/j.cnki.2095-8188.2024.05.005

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The rapid expansion of the service scope of the power grid control system has caused the explosive growth in power dispatching data.Data quality issues such as consistency and accuracy of measuring data have become increasingly prominent.Therefore,how to quickly and effectively realize the measuring data quality diagnosis and evaluation of multi-level power grid control has become an urgent issue.Focusing on the business requirements of multi-level power grid dispatching and control operation management,a measuring data verification algorithm considering long time scale power balance and multi-source correlation analysis is proposed to realize the rapid research and judgment of abnormal data such as power imbalance and multi-source inconsistency.Secondly,a measuring data quality evaluation method based on fuzzy analytic hierarchy process is proposed,and a comprehensive evaluation system of multi-source measuring data quality for grid control based on Spark is constructed,which can provide technical support for deep mining of data value and lean management of the control in large power grids.

Electrical Design & Discussion

Design and Implementation of Fast-Breaking Organic Thermal Fuse

PAN Xiaoning, LIU Xiangjun

2024, 0(5):  46-52.  doi:10.16628/j.cnki.2095-8188.2024.05.006

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In order to solve the problems of slow breaking speed and low DC breaking capacity of the existing organic thermal fuse,an organic thermal fuse with high breaking speed is designed.By introducing a contact driving part,cooperated with the springs the slow melting process of the thermal-sensitive is converted into the fast breaking action of the moving contact to improve the DC breaking capacity of the organic thermal fuse and make it applicable for DC circuit temperature protection.The influence of the springs on the moving speed of the moving contact is explored through the multibody dynamics simulation to guide the design of the prototype.Finally,the prototype of the thermal fuse is fabricated.The contact breaking speed test and DC load breaking experiment are carried out.The results prove that the designed thermal fuse has high breaking speed and certain DC breaking capacity.

Effect and Optimization on Short-Circuit Breaking Performance for MCB Shell Modification from Thermosetting to Thermoplastic

CHEN Changzu, ZHOU Chao, JIN Pingping

2024, 0(5):  53-60.  doi:10.16628/j.cnki.2095-8188.2024.05.007

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Aiming to study the influence of shell material characteristics (such as mechanical strength,high-temperature arc resistance,gas production and dielectric recovery strength) and shell structure on short-circuit breaking ability,based on the design of the miniature circuit breaker (MCB) shell material modifying from a thermosetting bulk molding compound (BMC) to a thermoplastic PA6 and the characteristics of a PA6 material,the shell structure is optimized.The short-circuit breaking test is carried out through the combination of different shell material and structure,then the testing data is obtained.Based on the test data and the disassembly information after testing,the relationship of the distribution and stability of arc time and energy in each stage of short-circuit breaking with the shell material and structure is studied by dividing the arc stages,the structure of a PA6 shell MCB is optimized.Finally,the short-circuit breaking test is passed.The experimental results show that the structure optimization of the thermoplastic modification is reasonable,which indicates that the analysis method of short-circuit breaking test is effective and has certain reference significance for the design and analysis of similar products.

Research on Hazards of Electromagnetic Coil Reverse Electromotive Force in Aircraft Switch Devices and Protection of Wiring Systems

MENG Xin, GUO Jing, ZHENG Zhichao, WANG Sai

2024, 0(5):  61-66.  doi:10.16628/j.cnki.2095-8188.2024.05.008

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Due to the lack of effective protection against the reverse electromotive force of switch devices in the aircraft wiring system,the safety issues have become increasiugly serious.Based on the burnout failure case of a certain type of relay on board.The generation mechanism and potential propagation path of the reverse electromotive force are studied.The damage modes to different devices such as coils,contacts,and circuit boards are analyzed.Through simulation and physical testing,the protective measures for different parts are developed.The selection criteria for protective devices are given.The protective effects are verified.The obtained conclusions have certain reference value for guiding the field maintenance and troubleshooting in the military,and urging the equipment manufacturers to optimize their products.

Design of Electricity Theft Monitoring System Based on RDBN Deep Learning Algorithm

CHEN Zhiqian, BAO Guanghai, FANG Yandong

2024, 0(5):  67-74.  doi:10.16628/j.cnki.2095-8188.2024.05.009

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Electricity theft not only leads to an increase in non-technical losses in the power grid,but also has the potential to impact the operational safety of power grid equipment and pose risks to the safety of individuals involved in power theft due to improper handling.The current power grid faces challenges in detecting electricity theft,including difficulty in inspections and low detection efficiency.In response to these issues,a power theft monitoring system is proposed.The associated monitoring device can be flexibly installed on power supply lines,utilizing a current transformer for power supply.It real-time collects current from the power line and transmits the data to a cloud server using a 4G module.The upper-level software employs the real-valued deep belief network (RDBN) algorithm for data analysis.Through simulation and experimental testing,the RDBN algorithm achieves a recognition accuracy of 98.15% for power theft states.The monitoring system can acquire and analyze monitoring data in real-time,mark suspicious power theft lines,reduce inspection difficulty,and improve detection efficiency.

Simulation Technology Application

Simulation Analysis on Dynamic Stability During Short-Circuit Closing Process of MTKS-ES

WAN Yongfeng, LÜ Pengrui, GUO Peng

2024, 0(5):  75-81.  doi:10.16628/j.cnki.2095-8188.2024.05.010

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Earthing switch (ES) is one of the widely used equipment in the power system,and its stability and reliability play an important role in the safe operation of the power grid.The dynamic stability simulation research on the short-circuit closing process of multi touch knife switch (MTKS) ES is conducted.Firstly,a simulation model of the short-circuit closing process of the ES is built and the characteristics of the current during short-circuit closing of the ES is analyzed.Secondly,the ES is used as the physical model to analyze the closing process status and perform the time-domain matching of short-circuit current.Finally,the dynamic stability during the closing process is simulated and analyzed.The results indicate that the time domain matching method for short-circuit current of ES can analyze the impact of short-circuit current on dynamic stability during the closing process of ES,which has certain guiding significance for the design and development of high capacity ES structures.

Research on Impact Resistance Performance of Marine AC Medium Voltage Vacuum Circuit Breaker

ZHOU Qiang

2024, 0(5):  82-87.  doi:10.16628/j.cnki.2095-8188.2024.05.011

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The impact resistance performance is the key to reliable operation of marine AC medium voltage vacuum circuit breaker under instantaneous impact.The initial test results of AC medium voltage vacuum circuit breakers is analyzed using a high-speed camera.Two kinds of impact resistance structure optimization schemes are designed.ADAMS multi-body dynamic simulation model is established for the operating mechanism and contact system of circuit breaker to complete the simulation analysis and optimization design of circuit breaker impact resistance process.Finally,combined with the impact testing verification,it is of great engineering significance to meet the impact resistance performance of circuit breakers.

Numerical Calculation of Converter Cooling System Based on Thermal Simulation

SONG Dongdong, GENG Lijun, YANG Shuanghan

2024, 0(5):  88-94.  doi:10.16628/j.cnki.2095-8188.2024.05.012

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With the increasing integration of power electronics and power density the new requirements are placed on the design of power electronics cooling systems.At present,there are some researches on the heat dissipation design of power electronic equipment,but there are still some problems in the calculation of thermal resistance,the lack of verification methods for thermal resistance calculation and the unreasonable selection of fans.Taking the design of the PWM converter cooling system as an example,a more complete thermal design process of the heat dissipation system is proposed.The calculation process of the heat resistance of the radiator and the selection of the fan are given.The simulation model is built by thermal simulation software.The resistance,temperature and fluid velocity are simulated and analyzed.Finally,the test platform is built to test the temperature data.The results show that the calculation,simulation and measured data have good consistency and meet the design requirements.