含高比例分布式电源的直流配电系统故障恢复过电压机理及其抑制

针对直流配电系统故障恢复过程中出现的过电压问题，本文研究了该过电压的产生机理及其抑制方法。首先介绍了典型直流配电系统的拓扑结构，给出两种核心换流装备(两电平VSC和DC/DC换流器)在双极短接故障下的电流及电压故障特征。基于故障点隔离后的健全区系统等效电路，研究了故障恢复过电压机理及影响因素，揭示了故障存续期间各换流器电压跌落速度不一致是导致故障恢复过电压的根本原因。在此基础上，以保障换流器电压跌落速度相同和直流断路器开断容量为约束，提出各换流器出口限流参数匹配设计原则，同时兼顾限制故障电流和抑制故障恢复过电压效果。最后在PSCAD/EMTDC进行了仿真验证。

Fault recovery overvoltage and its suppression in DC distribution system with high DG penetration

Aiming at the overvoltage during fault recovery of DC distribution system, this paper studies overvoltage generation mechanism and puts forward an overvoltage suppression method based on current limiting inductance matching design. This paper first introduces the topology of typical DC distribution system and gives the current and voltage fault characteristics of two core converter equipment (VSC and DC/DC converter) under bipolar short-circuit fault. Based on the equivalent circuit of the normal system after fault isolation, the generation mechanism and influencing factors of fault recovery overvoltage are analyzed. It is found that the root cause of fault recovery overvoltage is the inconsistent voltage drop rate of each converter during the fault. Then, the matching design principle of the outlet current limiting of each converter is proposed to ensure the same voltage drop rate of the converter and the breaking capacity of the DC circuit breaker. The fault current limiting and fault recovery overvoltage are also taken into account. Finally, the simulation results of PSCAD/EMTDC show that the proposed method has good overvoltage suppression effect.