一种新型电容换相混合式直流限流器

A Novel Capacitor Commutated Hybrid DC Fault Current Limiter

采用半桥型模块化多电平换流器的直流电网面临直流故障清除难题,高压直流断路器面临切除时间和切除容量的矛盾。为此,该文提出一种适用于抑制直流侧故障电流的混合式故障限流器(hybrid FCL)拓扑,并提出限流效果评价指标。具体而言,该限流器在稳态时负载电流通过低损耗支路通流,故障后通过负载转换开关使故障电流通过限流支路。限流支路是由晶闸管、换相电容和限流电感组成的H桥电路,其目的在于使用半控型电力电子器件节约投资,利用电容充放电来实现特定桥臂的导通和关断,最终使限流电感串联进入放电回路达到限流目的。对所提限流器工作原理、控制模式、电气应力和工程设计进行详细研究和仿真验证,表明所提出拓扑具备良好的工程应用前景。

To face the severe challenge of DC side fault current clearance in the DC grid based on half-bridge modular multilevel converter (MMC),strict demand has been proposed to fault detection and DC circuit breaker (DCCB).In this paper, a novel topology of hybrid fault current limiter (hybrid FCL) uses commutation capacitor along with a fault current-limiting index has been proposed.Specifically,the load "current flows through the low loss bypass path during normal operation, while turning off the load commutation switch (LCS),fault current commutates to the current limiting path.The current limiting path consists of three elements in a H-bridge circuit: thyristors,commutation capacitor and current limiting reactors. The proposed FCL use semi-controlled semiconductors to save investments,a commutation capacitor is used to control specific arm on and off through discharge and recharge process of the capacitor,the final goal is to make current limiting reactor in series with the system discharge circuit and prevent fault current rapidly rises.The principle,control method, electrical stress and preferences of proposed FCL have been studied in a converter station equivalent discharge module. Compared to other typical FCL,proposed hybrid FCL is considered to have good performance on current limiting and low investment demand.It can be adopted as a solution throughout the growing HVDC systems and DC grids.