Research On Adaptive Current Protection For Grid-connected Distribution Network With Photovoltaic

In the case of environmental pollution and the growing energy crisis,solar power has been greatly developed.The maturity of photovoltaic power generation technology has increased its penetration rate in the power grid,but the access of the photovoltaic system has changed the power supply structure of the distribution network,causing the flow direction and magnitude of the fault current to change,and the output instability of the photovoltaic power source is intensified.The threat to the stable operation of the system leads to the failure of the original relay protection of the system distribution network to cause refusal or misoperation.It is difficult to meet the basic requirements,damage the security and stability of the system,and limit the development of distributed power.Therefore,it is of great theoretical and practical significance to study the current adaptive protection of photovoltaic grid-connected distribution networks that can meet the performance requirements.This paper first builds a simulation model of grid-connected photovoltaic system on MATLAB/Simulink platform to ensure that functional modules such as PV array,MPPT and inverter can be realized;Secondly,to study the influence of grid-connected photovoltaic system on the fault characteristics and protection of distribution network,use the built-in photovoltaic grid-connected model to simulate,determine the photovoltaic system's active output and the implicit relationship between transition resistance and fault current can pass the photovoltaic system during the fault period.Equivalent impedance to reflect;Then,the data collected by the simulation is used as a training sample,and a plurality of machine learning algorithms are used to identify the equivalent impedance of the photovoltaic system during the fault online,and the optimal algorithm is compared and determined;Finally,based on the principle of current protection,a new strategy for adaptive current protection of photovoltaic grid-connected distribution network is proposed.The simulation results show that the proposed method can effectively improve the protection reliability of the distribution system connected to the photovoltaic system.The correctness of the current protection adaptive strategy is confirmed.