受端混联LCC-VSC特高压直流输电系统故障穿越方法

针对受端由电网换相换流器（LCC）和电压源换流器（VSC）级联的混合直流输电系统中VSC在交流故障穿越时子模块过压的问题，文中提出在受端VSC直流侧安装耗能设备以抑制VSC子模块过压的方法，对比分析了基于直流斩波耗能电阻、泄流晶闸管和可控避雷器3种耗能设备的交流故障穿越原理及策略。基于PSCAD/EMTDC仿真平台搭建了包含工程实际控制保护主机程序的受端混联LCC-VSC特高压直流仿真模型，对比分析了3种耗能设备的交流系统故障穿越特性，结果表明在受端VSC直流侧安装耗能设备可以有效抑制子模块过压，实现交流故障可靠穿越。其中可控避雷器方案具有控制原理简单、可靠性高等优点，更适用于受端混联LCC-VSC特高压直流输电系统。

Fault ride-through method of inverter hybrid cascade LCC-VSC UHVDC transmission system

In a hybrid cascade UHVDC transmission system which the receiving end consists of a line commutated converter(LCC) in series with multiple parallel voltage source converters(VSC),the VSC has sub-module overvoltage problems when the AC grid fault. A method to suppress the overvoltage of the sub-module by installing energy-consuming devices on the DC side of VSC is proposed. The fault ride-through principles and strategies based on energy-consuming devices as DC Chopper,thyristor and controllable metal oxide surge arrester (CMOA) are compared and analyzed. Based on the PSCAD/EMTDC simulation platform,a hybrid cascade UHVDC simulation model containing the actual control and protection host program is built,and the AC fault ride-through characteristics based on three energy-consuming devices are compared and analyzed. The results show that the method of installing energy-consuming devices on the DC side of the VSC can effectively suppress the overvoltage of the sub-module and achieve reliable AC fault ride-through. The CMOA scheme has the advantages of simple control principle and high reliability,and it is suitable to be the energy-consuming devices for the hybrid cascade UHVDC transmission system which the receiving end consists of LCC and multiple VSC.