A large number of photovoltaic power sources connected to the grid will increase short-circuit current level of power system, and its fault transient process will change the fault characteristics of power grid. In this paper, the equivalent models of transient and steady state faults are obtained, by analysing the full current expression of photovoltaic power sources and its current characteristics in different fault stages. Based on the superposition theorem, the short-circuit current calculation method of power system with photovoltaic power sources is proposed. Finally, the effectiveness of the proposed method is verified by the analysis of actual power grid calculation examples, and the results can be used for power grid planning and relay protection setting.

Short-circuit current of power system with photovoltaic power generation is related to the fault current provided by the photovoltaic power supply. In this paper, based on the analysis of low voltage ride-through uncertain region of photovoltaic power generation, the random model of low voltage off-grid is constructed. Further combining with the system fault information, based on the monte carlo simulation, a probabilistic assessment method of short-circuit current in power system is proposed, which takes into account uncertainty of photovoltaic low voltage ride-through. Finally, an example is given to verify the proposed method. The method in this paper comprehensively considers the random factors of power grid failure and photovoltaic power generation low voltage off-grid, and the short-circuit current result can accurately reflect actual short-circuit current level of the system.