Study On Protection Strategy Of Photovoltaic Power Generation System Connected To Distribution Network

At present,the energy and environmental problems are more prominent.In order to alleviate the energy and environmental problems,it is urgent to develop new energy without pollution.Solar energy is an ideal new energy,so the development of photovoltaic power generation is relatively rapid in recent years.In theory,photovoltaic power generation system can be installed in any place with sunshine,so the position of photovoltaic power generation system is relatively flexible when connected to the system.Photovoltaic power generation system will affect the normal operation of current protection in the distribution network system after being connected to the distribution system,which will reduce the security of the distribution network.This paper studied the theoretical model of photovoltaic cells by consulting literatures,and established the simulation model of photovoltaic power generation system by MATLAB/Simulink.After establishing the simulation model,the output of photovoltaic cell simulation model was measured by changing the input of light radiation intensity and temperature,and the correctness of the simulation model was verified.Learn the maximum power point tracking and inverter control method of photovoltaic power generation system,and establish the simulation model of photovoltaic power generation system.Theoretical analysis of three-phase current protection,and then photovoltaic power generation system short-circuit current simulation analysis.Through simulation and analysis,it is found that three-phase current protection is not used with photovoltaic power generation system.Therefore,a method to protect photovoltaic power generation system by the current value at the previous moment is proposed.By means of simulation,the influence of photovoltaic power generation system connected to distribution network is analyzed.Asymmetric and symmetric faults in distribution network are analyzed by means of compound sequence network,and the current protection setting value of the system is studied by means of compound sequence network diagram.On the basis of composite sequence network analysis,the current distribution of photovoltaic power generation system acting on the fault line alone is analyzed by superposition theorem.The distribution of output current of photovoltaic power generation system in the case of short circuit is calculated.The superposition of current provided by photovoltaic power generation system and current of the original system is analyzed by vector method.After the photovoltaic power generation system is connected,it will become a multi-power system.In the multi-power system,the power direction is uncertain.In order to determine the power direction,the power can be judged by the phase difference between current and voltage.Protection of photovoltaic system access after the process is analyzed,through the simulation analysis,the different power,photovoltaic power generation system output circuit of the current situation,and the current of the fault simulation,the simulation analysis found that the greater the power of photovoltaic power generation system output to the system,the more obvious,the influence of the output power reaches a certain worth,protective devices in the power distribution system will be false action,and then through the vector method to modify current protection device,the adjusted current protection setting value can meet the requirements of selectivity can also meet the requirements of sensitivity.