一种交直流混合输电系统直流侧双极故障保护策略

DC-side Bipolar Fault Protection Strategy for AC/DC Hybrid Transmission System

为进一步分析含柔性直流输电(MMC-HVDC)的交直流混合输电系统的故障特征,基于交直流混合输电系统和模块化多电平换流器(MMC)的拓扑结构,推导了MMC的数学模型,研究了直流系统双极短路的故障机理和故障特征,针对含MMC-HVDC的交直流混合输电系统的双极短路故障,设计了限流电路及闭锁换流站与交流断路器跳闸相结合的故障保护方案。以厦门市柔性直流输电系统为例,在PSCAD/EMTDC中搭建了交直流混合系统,并对保护方案进行了仿真验证。结果表明,提出的保护策略能有效地降低故障电流,提高系统稳定性。

To further analyze the fault characteristics of the AC/DC hybrid transmission system with flexible direct current transmission(MMC-HVDC),this paper derives the mathematical model of MMC,and studies the fault mechanism and fault characteristics of DC system bipolar short circuit,based on the topological structure of AC/DC hybrid transmission system and modular multilevel converter(MMC).Aiming at the bipolar short-circuit fault of the AC/DC hybrid transmission system containing MMC-HVDC,a fault protection scheme combining current-limiting circuit and blocking converter station with AC circuit breaker trip was designed.Taking the Xiamen flexible DC transmission system as an example,an AC/DC hybrid system is built in PSCAD/EMTDC,and the protection scheme is simulated and verified.The results show that the proposed protection strategy can effectively reduce the fault current and improve the system stability.