光伏中压直流汇集系统双极短路特性分析及连锁过电压抑制

为了解决光伏中压直流汇集系统直流变压器中压侧双极短路故障问题,根据系统拓扑划分为直流线路送端和受端2种情形展开详细讨论,通过不同的故障回路计算出双极短路时网侧和机侧对短路点的故障电流分量,给系统保护的参数整定提供依据,进一步分析了其直流低压母线连锁过电压产生机理,并提出过电压的有源抑制方法,避免了光伏阵列频繁解列。仿真结果表明,换流站和直流变压器出口处配置限流电抗器可大幅降低短路电流的上升速度,通过改变光伏模块的稳态工作点可迅速抑制低压直流母线电压上升。论文研究可为中低压直流配网示范工程建设新能源汇集提供理论及技术支撑。

Characteristic Analysis and Chain Overvoltage Suppression for Bipolar Short Circuit in Photovoltaic MVDC Collection and Integration System

In order to solve the bipolar short-circuit fault problem on the DC transformer medium-voltage DC(MVDC) side of the photovoltaic MVDC collection system, this paper discusses the bipolar short circuit problem at the sending terminal and receiving end of DC cable, respectively. The contributions of the MVDC short circuit current at the fault point are quantitatively analyzed by different fault circuits, which provides a reference for parameter setting of protection devices. Furthermore, the mechanism of DC low-voltage bus overvoltage is analyzed, and an overvoltage active suppression method is proposed to avoid frequent photovoltaic arrays from cutting off from the system. The simulation results show that the current limiting reactor at the MVDC side of the converters can reduce the rise speed of short-circuit current greatly. By changing the operation point of the PV module, the voltage rise of the low-voltage DC bus can be quickly suppressed. The research can provide theoretical and technical supports for the renewable power generation construction of medium-voltage and low-voltage DC distribution network demonstration project.