PV System Output Modeling and Influence Factor Analysis of Metallic Bipolar Short-Circuit Fault for DC Microgrids

For DC microgids, the characteristics of bipolar short-circuit faults are a key factor for the design of protection schemes and the selection of power electronic devices. Scholars have performed many studies on the fault characteristics of the voltage source converter (VSC) on the AC system, whose IGBT is immediately blocked after the bipolar short-circuit fault occurs. However, there are few researches on the photovoltaic(PV) system output modeling of bipolar short-circuit fault. This article presents a PV system output analysis model, focusing on the metallic bipolar short-circuit fault for DC microgrids. Firstly, according to the diodes feeding progress of the DC/DC converter on the PV side, the whole metallic bipolar short-circuit fault process is divided in detail. Then, accurate state equations are established by the equivalent circuits of different transient stages. PV source output characteristic is expressed piecewise linearly, and the expressions of each electrical fault variation are provided. Finally, a simulation model is constructed using MATLAB/Simulink software. The effectiveness of proposed model is validated with simulation results, showing that its high accuracy for different fault locations, illumination strength, ambient temperatures and fault resistances.