应用于直流电网的直流断路器参数选取研究

混合式高压直流断路器所能承受的电流水平不仅反映了整个网络向故障点的馈能情况,同时也是其内部各开关器件承受能力的外在体现。直流电网的稳态潮流分布及故障时的电流变化情况则是高压直流断路器载流支路及主断路器支路参数选取的重要依据。本文以直流电网潮流分布为基础,考虑了直流电网可能存在的多种运行方式,分析了高压直流断路器承受的稳态电流水平,进而为其载流支路参数选取提供参考。同时,在基于半桥子模块结构的换流器故障机理分析的基础上,进一步研究了直流电网线路发生故障时的网络电流、换流器出口电流及换流器桥臂电流的变化情况,为高压直流断路器所需开断故障电流水平提供理论依据,并为高压直流断路器的主断路器支路参数及限流电感参数整定及其与换流站闭锁保护相互配合提供一定的参考。最后,在PSCAD/EMTDC仿真平台搭建的四端环网模型上验证了所提方法的正确性。

Research on Current Parameters of DC Circuit Breaker for DC Grid

The current stress level of hybrid HVDC circuit breaker not only reflects the energy supply to the fault point of the whole network, but also reflects the bearing capacity of the internal switching devices. To a DC grid with certain voltage level, the steady-state power flow distribution and the fault current variation of DC power network are important bases for HVDC circuit breaker selection. Based on the power flow distribution of DC grid, the current stress level of HVDC circuit breaker is analyzed considering the possible operation modes of DC grid. At the same time, based on the analysis of the fault mechanism of the converter based on the half-bridge submodule structure, this paper makes a further research on the variation of network current, outlet current of a converter and bridge arm current, in order to provide the theory basis of bearing of fault current stress level of high voltage direct current circuit breaker, and then provides reference for parameter setting and mutual cooperation between HVDC circuit breaker and converter overcurrent protection. Finally, the feasibility of the proposed theory is verified on the four-terminal network model built by PSCAD/EMTDC simulation platform.