一种适用于直流电网的阻容型混合式限流器

A Resistive and Capacitive Hybrid Current Limiter for DC Power Grid

针对直流电网采用直流断路器进行故障隔离的优势和挑战,介绍了直流限流方案的研究现状。当模块化多电平换流器(modular multilevel converter,MMC)直流侧发生双极短路故障时,故障电流在两三个毫秒内上升至额定电流的十几倍甚至几十倍,由于直流断路器有一定的动作延时,因此有必要在直流回路中设置限流器。对发生上述故障时限流器的运行参数进行了分析,利用混合式通流支路通态损耗低、动作速度快,以及阻容型元件能平滑限流器电压上升速率的特性,提出了一种适用于直流电网的阻容型混合式限流器,分析了该限流器的工作原理和内部开关电压应力情况。最后,在PSCAD/EMTDC仿真平台中搭建了四端直流电网模型及所提的限流器模型,仿真结果表明采用所提限流器能够降低故障电流、缩短保护时间,验证了理论分析的正确性和限流方案的可行性。

In view of the advantages and challenges of using DC circuit breakers for fault isolation,this paper introduces the research status of DC current limiting solutions.When there is a bipolar short-circuit fault current at the DC side of a modular multi-level converter(MMC),the fault current will rise to a dozen or even dozens of times of the rated current in two or three milliseconds,because of a certain action delay of the DC circuit breaker,it is necessary to set up current limiter in DC circuit.The parameter of current limiter is analyzed the above fault occurs,taking advantage the characteristics that a hybrid flow through branch has low on-state losses,fast operating speeds,and the ability of the resistive-capacitive element to smooth the voltage rise rate of the current limiter,a resistance-capacity hybrid current limiter for DC power grid is prensented,the working principle of the current limiter and internal switch voltage stress are analyzed.Finally,a four-terminal DC grid model and the proposed current limiter model are built in the PSCAD/EMTDC simulation platform,the simulation results show that the proposed current limiter can reduce the fault current and shorten the protection time,and the correctness of the theoretical analysis and the feasibility of the current limiting scheme are verified.