光伏直流并网系统外部故障切除后有功恢复控制方法

Active Power Recovery Control Method for Photovoltaic DC Grid-connected System After External Fault Clearance

光伏直流并网系统的集控信号局部丢失时,光伏单元难以在交流电网线路故障切除后恢复原有控制模式。为此,在分析恢复过程直流电压变化特性基础上,提出一种光伏直流并网系统外部故障切除后有功恢复控制方法。该方法利用直流电压阈值以及变流器固有动态响应时间,构成控制模式切换综合判据,以实现不同电网电压跌落程度下光伏单元控制模式的可靠切换。所提方法优势在于充分利用了变流器固有响应时间,不受交流故障过渡电阻影响,且无需改变变流器的控制器结构。仿真结果表明,所提方法在不同电网电压跌落下,均可有效实现故障清除后光伏单元控制模式的切换。

When the centralized control signal of the photovoltaic(PV)DC grid-connected system(PV-DCGS)is partially lost,it is difficult for PVs to restore the original control mode after AC grid line fault clearance.Therefore,based on the analysis of the characteristics of DC voltage changes during the recovery process,a control method for active power recovery after external fault removal in PV-DCGS is proposed.This method utilizes the DC voltage threshold and the inherent dynamic response time of the converter to form a comprehensive criterion.The PV’s control mode can be switched reliably under different grid voltage dips.The advantage of the proposed method is that the inherent response time of the converter is fully utilized and can still be available under different fault transition resistances.What’s more,changing converter’s controller structure is not required.The simulation results show that the proposed method can effectively switch PV’s control mode under different grid voltage dips after fault clearance.