含VSC-HVDC的混合MIDC系统强度计算及仿真分析

System Strength Calculation and Simulation Analysis in a Hybrid Multi-infeed HVDC System with a VSC- HVDC Link

针对多馈入直流(MIDC)系统在受端交流电网故障易引发一回或多回直流换相失败,将电压源换流器高压直流(VSC-HVDC)引入到MIDC系统中,改善LCC-HVDC逆变侧母线电压特性。建立了考虑受端系统负荷特性的简单混合MIDC系统详细模型,可将此作为未来MIDC系统的一个子单元。理论推导了该模型的有效短路比(ESCR),提出了近似计算方法。最后借助于PSCAD/EMTDC仿真,分析了LCC-HVDC逆变侧发生三相短路,简单混合MIDC系统的动作特性;研究了逆变站在不同电气距离下,LCC-HVDC换相失败免疫性指标(CFII),并以CFII验证了近似计算方法的有效性。结果表明,混合MIDC系统有助于提高ESCR,增大CFII,减少换相失败几率。

Aim at one or multiple loop HVDC system commutation failure caused by receiving-end AC power network fault of the multi-infeed direct current（ MIDC）,voltage source converter based HVDC（ VSC-HVDC） was applied to this MIDC systems in this paper for improving the voltage characteristic of the Line Commutated Converter High Voltage Direct Current,（ LCC-HVDC） inverter bus. A simple hybrid multi-infeed HVDC（ HMIDC） detailed model was set up,as a unit of the MIDC in the future. The effective short-circuit ratio（ ESCR） of the HMIDC system was deduced by theoretical formula,and proposed an approximate calculation method. Eventually,via PSCAD / EMTDC simulation,analyzed the performance characteristic of the simple HMIDC system at three-phase short circuit of the LCC-HVDC inverter side and studied on commutation failure immunity index（ CFII） of different length electric distance,and verified the effectiveness of approximate calculation method by CFII. The results show that the HMIDC system can help enhance the ESCR,increase CFII and reduce the chance of the commutation failure.