Effects Of Grid-connected Photovoltaic System On Distribution Network Protection And Its Countermeasures

The distributed generation based on clean and renewable energy is not only an indispensable and effective complement to centralized power generation, and of great strategic significance to alleviate the increasingly serious energy and environmental issues. Solar energy is unmatched by other energy sources which are used by distributed power generation because of it is broad, unlimited and economy. So the solar photovoltaic power has aroused much worldwide attention, and is recognized with high technological content, as one of the most promising technologies. With photovoltaic technology gradually mature and the cost of power generation reduced ceaselessly, the grid-connected photovoltaic system has become the mainstream trends in solar energy development and utilization. However, the output power of the photovoltaic power generation system is susceptible to external environmental conditions.When the large-scale, high-capacity photovoltaic systems connected the grid must bring distribution network a series of issues and challenges, one of which is the influence on the distribution network protection, because the grid-connected photovoltaic system changes the original network structure and power flow of the distribution network, which may change the fault current magnitude, flow direction and duration,direct impact on the protective properties of the relay device, damage the co-ordination between protection and automatic safety devices. In order to ensure the safe and stable operation of distribution network, as well as to promote the applications of thegrid-connected photovoltaic system technology, The paper launches the research on the effects of grid-connected photovoltaic system on distribution network protection.With the distribution network using different protection configuration scheme,the effects of grid-connected photovoltaic system on relay protection and automatic safety devices when failure occurs are firstly analyzed in the paper. Then distribution network fault current changes are analyzed and the conclusion of the effects of grid-connected photovoltaic system on distribution network fault current is drawn according to different photovoltaic system access locations, different access capacity, different fault locations in distribution network.The existing protection scheme of distribution network with photovoltaic system based on whether to allow the island running to classify and be described.Based on wide area measurement system protection scheme is Proposed. The scheme to improve the existing distribution network protection configuration and use of wide area measurement system to collect multi-point protection action information to conduct the comprehensive determine the accurate location of the fault, thereby preventing protection malfunction.When a permanent fault occurs, a short time off the power supply mode is used to form island running.It gives full play the positive role of the photovoltaic power and improves the safety and reliability of the distribution network power supply.