An Emergency Control Strategy for Multi-PV Grid-Connected System Considering Active Power Injection under Short-Circuit Faults

Regarding the phenomenon of the serious voltage sag at the connection point when a three-phase short-circuit fault occurs at the AC side of the grid-connected PV system with multiple power levels, an emergency control strategy considering active power injection is proposed. Firstly, based on the traditional low-voltage ride through (LVRT) strategy, a new LVRT control strategy considering active power injection is proposed. Combined with the power control strategy of a typical PV inverter, an emergency control system model of a multi-PV grid-connected system is established. Secondly, the dynamic behaviors of the AC side voltage and output power of the PV inverter are extracted and analyzed before/after the short-circuit fault at the load-side. After that, an emergency control strategy of multi-PV grid-connected system considering active power injection is proposed based on the centralized coordinated control method. This strategy takes into account the power difference of multiple PV subsystems, and then determines the output of the PV reactive current settings. Finally, the simulation results show that the proposed strategy can ensure reactive power support to improve the voltage continuity during the three-phase ground fault and simultaneously take the active power output efficiency into account, which is beneficial to reduce the impact of the traditional LVRT strategy on active power injection when providing voltage support.