多端VSC-HVDC直流线路故障限流及限流特性分析

Fault Current Limitation and Analysis of Current Limiting Characteristic for Multi-terminal VSC-HVDC DC Lines

基于电压源型换流器(voltage source converters,VSC)的多端柔性直流系统中直流线路的故障电流上升速度快、电流峰值大。然而具有大容量、快切断能力的高压直流断路器正在研制中。结合目前直流断路器开断容量水平,该文提出通过在直流线路两端串入限流电路的方法来限制故障电流的峰值和电流的上升速度率,并给出相关参数的理论计算方法。对该电路的限流特性进行分析与对比,结果表明,该限流电路能有效抑制故障电流,降低了对直流断路器开断容量和开断速度的要求。在该限流电路的基础上,提出一种多端VSC-HVDC直流线路故障处理方案。仿真分析表明,该故障处理方案能够有效抑制直流线路故障电流以及IGBT并联二极管电流,故障切除后非故障系统能保持正常运行,可以有效地增强多端VSC-HVDC系统对直流线路故障的处理能力。

The fault current of DC line in multi-terminal HVDC system based on voltage source converters (VSC) increases quickly with large peak, while the DC circuit breaker with large capacity and fast breaking speed is still under development. Combined with the capacity level of DC circuit breaker breaking, a current limiting circuit was proposed to limit the peak and rising rate of fault current by connecting it to DC line ends. Theoretical calculation method for the circuit parameters was also given. The analysis results about the circuit and the comparison with other methods show that the proposed circuit is able to limit the fault current effectively and reduce the requirement for DC breaker capacity and speed. Based on the circuit, a fault-handling scheme for DC lines in multi-terminal VSC-HVDC was proposed. The simulation results show that the proposed scheme is capable of limiting fault current of DC lines and parallel diodes effectively, and non-fault system can maintain normal operation after fault clearance, indicating that the handling ability of multi-terminal VSC-HVDC system for DC fault is enhanced effectively. © 2016 Chin. Soc. for Elec. Eng.