混合式高压直流断路器快速限流优化方案及仿真分析

Fast Limit Current Optimization Scheme and Simulation Analysis of Hybrid HVDC Circuit Breaker

混合式高压直流断路器分断速度快且通态损耗低,能够保证不闭锁换流站的情况下实现线路故障的快速隔离,减小故障范围,是直流电网保护的关键设备之一。首先研究了含混合式直流断路器的柔直系统直流故障限流机理,分析影响直流故障电流峰值以及故障电流持续时间的关键因素,并在现有混合式高压直流断路器基础上,提出一种快速限流的优化技术方案,在转移支路加入故障限流子模块(fault current limiter submodule,FCL_SM),FCL_SM由二极管桥、限流电阻以及限压电路组成,通过在故障过程中投入FCL_SM来降低故障电流峰值以及MOV吸收能量。最后通过PSCAD/EMTDC仿真分析,验证了所提优化方案的可行性与有效性。仿真结果表明,优化方案可有效降低直流故障电流峰值(降低幅度达14%)、故障电流持续时间以及直流断路器MOV吸收能量(降低幅度达16.2%),并可有效降低设备设计成本。

Mixed high breaking speed and low conduction loss type hybrid DC circuit breaker, which can guarantee the realization of line fault isolating converter without blocking, reduce the scope of fault, is one of the key equipments of MMC-HVDC protection. Firstly, the DC fault current limiting mechanism of the MMC-HVDC system with hybrid DC circuit breaker is studied. Then based on the existing hybrid DC circuit breakers, an optimized technical scheme for fast current limiting is proposed. In the transfer branch join fault current limiting submodule(FCL_SM), the FCL_SM consists of a diode bridge, a current limiting resistor and a voltage limiting circuit. The FCL_SM is used to reduce the peak value of the fault current and the energy absorbed by the MOV. Finally, the simulation analysis is carried out by PSCAD/EMTDC, and the feasibility and effectiveness of the proposed optimization scheme are verified. The results show that the optimization scheme can reduce the DC fault current peak(decreased by 14%), the duration of the fault current and DC circuit breaker MOV energy absorption(decreased by 16.2%), and can effectively reduce the cost of equipment design.