A Linear Equivalent Method of PV Array for Fault Analysis of Medium-Voltage Networks

In order to establish a photovoltaic(PV) grid-connected system model that is suitable for studying faults in medium-voltage distribution networks, it is advisable to conduct linearized and simplified equivalent research on each component of the PV grid-connected system according to specific fault scenarios. The primary focus should be on linearizing and simplifying the modeling research of the PV array, which serves as the energy supply link. The impact of medium voltage distribution network faults on the PV array output is analyzed, and the maximum power point(MPP), short circuit current point, and open circuit voltage point are identified as key parameters. The output equation of the non-ideal PV array is used to derive the equivalent formula for these parameters. By statistically analyzing the equivalent curve under different PV parameters, a linear relationship is established between the intersection point of the linear equivalent curve and the voltage and current of the MPP, based on statistical analysis of the equivalent curve under different PV parameters. Based on this relationship, a simplified calculation method for the equivalent curve parameters is proposed. Finally, the limitations of traditional equivalent methods are analyzed using examples, simulations and RTDS experiment, and the accuracy of the proposed calculation method is validated. Compared to existing modeling methods, the proposed method is specifically designed for medium-voltage fault scenarios. While ensuring the simulation output, it greatly simplifies the PV array model and its parameter calculation method, reduces the difficulty and calculation of theoretical and simulation research, laying the foundation for further simplifying the PV grid-connected system model.