The probabilistic short-circuit current (PSCC) of photovoltaic generation is determined by the voltage sag at the grid connection and the low voltage ride-through of the unit during the grid fault, while the voltage sag and the low voltage ride-through are both stochastic. According to short-circuit current characteristics and Thevenin equivalent circuit in the transient state, this paper analyzes the changing trajectory of the equivalent internal potential of photovoltaic generation during the period of low voltage ride-through. To deal with the uncertainty of low voltage ride-through, the probability density function by the maximum entropy method is used to characterize the stochastic process of low voltage disconnection of photovoltaic generation. Based on the fault information, the calculation method of PSCC in active distribution network considering the uncertainty of low voltage ride-through of photovoltaic generation is proposed. Two cases of 9-node and 34-node distribution network are used to verify the effectiveness of the method. The obtained PSCC results can reasonably reflect the actual short-circuit current level of the active distribution network.INDEX TERMS Photovoltaic, probabilistic short-circuit current, low voltage ride-through, active distribution network.

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.

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