基于模块化多电平换流器的直流系统故障电流分析及故障穿越测试

半桥型模块化多电平转换器(half-bridge modular multilevel converter,HBMMC)具有阻止直流链路中的短路的能力,而全桥型模块化多电平转换器(full-bridge modular multilevel converter,FBMMC)可以产生双极性电压从而阻止直流链路中的短路电流快速清除直流侧故障,是实现直流故障穿越的理想拓扑。研究极间短路故障的特征及其数学模型,提出计算故障电流的改进分析法。基于临界故障电阻分析,研究模块化多电平换流器(modular multilevel converter,MMC)的传输系统的直流短路穿越的能力。分别模拟两种运行模式:第一种运行模式中MMC可以用无功功率支持交流电网,但不会传输有功功率;第二种运行模式中MMC可以在故障期间传输有功功率。在PSCAD/EMTDC软件中构建FBMMC-HVDC仿真模型,验证所提概念的可行性。

DC Short Circuit Ride-through Strategy For A Full-Bridge MMC HVDC Transmission System

Half-Bridge Modular Multilevel Converter (HBMMC) has the ability to prevent short circuit in DC link, while Full-Bridge Modular Multilevel Converter (FBMMC) can generate bipolar voltage to prevent short circuit current in DC link and quickly remove DC side fault, which is an ideal topology to realize DC fault ride-through. Firstly, this paper studies the characteristics and mathematical model of inter-pole short circuit fault, and proposes an improved analysis method for calculating fault current. Furthermore, the control strategy of MMC is analyzed, and a DC short-circuit fault ride-through strategy for HVDC transmission system with FBMMC topology is proposed. Simulate two operation modes: MMC can support AC power grid with reactive power in the first operation mode, but will not transmit active power; In the second operation mode, MMC can transmit active power during a fault. The FBMMC-HVDC simulation model is built in PSCAD/EMTDC software to verify the feasibility of the proposed concept.