Research On Influence Of PV Grid-connected On Wuzhong Power Distribution System Relay Protection And Automatic Contrivance

With the global emergence of lack of energy source, environmental pollution and other problems, it becomes a very important form of electrical source to use solar energy to yield Photovoltaic (PV) grid power in large-scale, which has its unique advantages. However, PV power system with traditional grid connected distribution networks will certainly change the topology structure of the original distribution system, and then it futher affects distribution network protection and correct act of automatic device. So, it is very necessary to study the influence of photovoltaic system over relay protect and automatic device in fault diagnosis for distribution network. It has practical significance for extension of photovoltaic techniques and guarantee of safe and reliable run of distribution network. The thesis takes the practical example of PV power station connected to some110kV transformer substation in Wuzhong in the Ningxia Hui Autonomous Region to carry out an intensive study.Firstly, studying equivalent circuit simulation model of photovoltaic batteries built through MATLAB,and by changing temperature of photovoltaic cell array and sunshine intensity, the output characteristic curve U/I and U/P of Photovoltaic cell array can be drawn.Comparing and defining the maximum power point track approach of photovoltaic cell model.Secondly, analysing theoretically the influence of photovoltaic system with variors volume, grid connection, detect faulty points and corresponding instability time on original relay protection of power distribution system. Studying the influence of photovoltaic system grid connection on coil in reclosing. The following conclusions are drawn. The first is that distribution of short-circuit current increment, or grid connection capacity, supplied by photovoltaic system for faulted line is the key factor that influences setting calculation of distribution systems protection. The second one is that influence degree on3-sectional current protection and distance protection depends on instability time of PV power system. Applying power network model with photovoltaic system established by PSCAD/EMTDC software to the simulation verification of the conclusion.Finally, illustrating basic switching principles of automatic switching device of stand-by power. Studying the influcence of PV power system through transformer substations with different voltage bus grid connection on switching control of coil in automatic switching device of stand-by power, inner bridge circuit breaker and transformer automatic switching device of stand-by power. Taking CSC-246A automatic switching device of stand-by power produced by Beijing Sifang Automation Co., Ltd as an example, altering the return circuit of automatic switching device of stand-by power and action logic, solving the effect of PV system grid connection on automatic switching device of stand-by power. The result shows that it can increase power distribution reliability of distribution network.