特高压混合直流输电系统整流侧交流故障控制策略

AC Fault Control Strategy on Rectifier Side of UHV Hybrid DC Transmission System

在特高压直流工程中,逆变站采用模块化多电平换流器(MMC)、整流站沿用电网换相换流器(LCC)构成特高压混合直流输电系统是解决受端交流电网多直流馈入问题、提高电网安全稳定性的一种有效方案。首先对特高压混合直流输电系统拓扑结构、基本控制模式以及整流侧交流故障时功率快速下降问题进行了阐述。然后在分析混合型MMC换流器串联控制特性的基础上,提出了基于直流调制度的交流故障控制策略,该策略通过在整流侧交流故障期间同步调整逆变站串联换流器直流调制度,维持直流电流的稳定并减小直流传输功率下降幅度,降低故障对交流系统的冲击。最后通过RTDS实时数字仿真试验平台验证了所提策略的有效性。

In the UHVDC project,the hybrid UHVDC transmission system composed of modular multilevel converter(MMC)used in the inverter station and line commutated converter(LCC)adopted in the rectifier station is an effective scheme to solve the problem of multi-infeed DC problem of the receiving-end AC grid and improve the security and stability of the power grid.Firstly,this paper expounds the hybrid UHV DC transmission system’s topological structure,the basic control mode and the problem of rapid power decline in time of AC failure on rectifier side.Then,based on the analysis of series control characteristics of hybrid MMC,the paper proposes an AC fault control strategy based on DC regulation system.This strategy synchronously adjusts the DC regulation degree of the inverter station series converter during rectifier-side AC failure to maintain the stability of DC current,thus reducing the descent range of DC transmission power,and decreasing the impact of failure on AC system.Finally,the effectiveness of the proposed strategy is verified by the RTDS real-time digital simulation test platform.