适用于直流电网故障清除的增强型MMC

随着直流输电系统电压和容量的提高,对直流故障快速清除隔离的要求越来越高。作为清除直流故障的有效方案之一,直流断路器(DCCB)技术还不够成熟,限制了其在工程上的应用。文中提出了适用于直流电网故障清除的低成本直流故障清除方案,对半桥型模块化多电平换流器(MMC)进行了局部的改造,以使其具备故障清除操作的能力,使得线路上的故障电流能够被低成本故障隔离单元迅速隔离,随后建立和分析了故障隔离过程中的等效电路,设计了故障隔离动作时序,并对比分析了典型方案的器件使用量,最后建立了仿真和实验模型。仿真和实验结果证明了该方案的有效性。

An Augmented Modular Multilevel Converter for Clearing Fault in DC Grid

With the increase of voltage and capacity of high voltage direct current (HVDC) system, the requirement for rapid clearance and isolation of DC faults is getting higher and higher. As the most effective solution, hybrid DC circuit breaker is not mature enough, which restricts its engineering application. Accordingly, this paper proposes a low-cost DC fault clearance scheme suitable for clearing fault in DC grid. In this scheme, the traditional half-bridge modular multilevel converter (MMC) is partially innovated to have the ability of auxiliary breaking operation. With the effect of the MMC auxiliary breaking operation at both ends of the fault line, the DC fault current can be quickly interrupted and isolated by low-cost circuit breaker unit installed in the DC transmission line. The equivalent circuit in the fault isolation process is modelled and analyzed, and the fault isolation sequence is designed. Furthermore, the comparative analysis of devices usage among typical schemes is performed. Finally, a simulation model with the proposed scheme is built, and an MMC prototype is developed. The simulation and experimental results validate the effectiveness of the proposed scheme.