| Photovoltaic power is a power generation mode which is strongly advocated in recent years in our country.More and more Distributed Generation(DG)is connected to distribution network,and its influence on power grid will also increase.The distribution network has changed from single power supply to multi-power supply.The access location,capacity and operation mode of distributed generation will have a great impact on the line power flow of the distribution network and the size of short circuit current in case of failure.Therefore,the traditional three-stage current protection connected to the distribution network of distributed generation may cause incorrect operation or rejection of operation.Thus,the protection fails,causing the fault can not be removed in time,and may cause major accidents.This protection scheme has been unable to meet the requirements of remote,real-time,self-healing,rapid and accurate relay protection.Based on the current development status and demand of the distribution network,this thesis studies the output characteristics of the distribution network before and after it is connected to the inverter distributed generation,and analyzes the influence of the distributed generation to the distribution network.In order to solve the problem of traditional three-stage current protection failure after distributed generation access,a current remote protection monitoring system suitable for distributed power distribution network is designed.In order to study the output characteristics before and after the distribution network is connected to the inverter distributed generation,the simulation model of 10 k V distribution network with inverter distributed generation is built through Power Systems Computer Aided Design(PSCAD).For the traditional distribution network without distributed generation and the distribution network with distributed generation,the change of fault current under different types of faults and the same type of faults is compared respectively,and the influence of distributed generation access on the distribution network is analyzed.It is concluded that the traditional three-stage current protection is not suitable for the distribution network with a large number of distributed generation access.In order to solve the problems of misoperation and rejection of traditional three-stage current protection in distribution network including distributed generation,an overcurrent protection scheme of distribution network including distributed generation is proposed.This scheme is a current protection scheme based on distribution network automation.It combines the grid geographic information system and terminal data collection to calculate the protection value in real time and set it remotely,improves the traditional three-stage current protection,and realizes the normal operation of the current protection in the distribution network after the access of distributed generation.At the same time,the current protection device based on STM32 is designed,and the physical model is built to simulate the function of the protection device,and verify the feasibility of the design.The design of remote current protection monitoring system including distributed power distribution network provides ideas and directions for further research on distribution network automation and self-healing technology. |
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