直流故障下全桥型多电平换流器模块电压分析

Analysis of Submodule Capacitor Voltage Caused by DC Pole-to-pole Fault in FBMMC HVDC System

基于全桥子模块的模块化多电平换流器(FBMMC)在闭锁后可以提供与电流方向相反的反电动势,是保持交流断路器不跳开的情况下实现柔性直流输电系统直流侧故障穿越的理想拓扑。通过对全桥拓扑子模块(FBSM)的工作模式和FBMMC控制方法进行研究,分析了直流故障发生后FBMMC中子模块电容电压的发展情况,分析结果表明,故障后模块电压会先后经历跌落和抬升两个过程,该发展过程对于直流故障检测方法、子模块电容耐受电压、模块过欠电压保护值等的工程设计具有重要意义,也是能否成功实现直流故障穿越的重要因素。最后的计算和仿真结果表明,文中的分析结果是正确的并且具有较高的精度。

DC link faults ride through is one of the most important research objects in modular multilevel converter HVDC system. The HVDC system based on full-bridge sub-module（FBMMC HVDC）can provide counter electromotive force opposite to the current direction after the sub-modules blocked. Therefore it is an ideal topology to fast clearance the DC link faults without opening of the AC circuit breaker. This paper analyzed the sub-module capacitor voltage for FBMMC HVDC at the situation of DC pole-to-pole short circuit fault. The result shows that the module voltage will experience successively drop and uplift. This process is significance for the design of DC fault detection method, the sub module capacitance voltage tolerance, and the sub-module over and under voltage protection value etc. It is also an important factor to the successful implementation of the DC fault ride through.Calculation and simulation show that the results of the analysis result is correct and has a high accuracy.