并联混合直流系统无功控制研究

Study on the Reactive Power Coordinated Control in Hybrid Parallel HVDC System

并联混合直流系统采用常规直流和柔性直流并联结构,综合了常规直流和柔性直流各自的优势。在高压直流输电系统现有无功控制的基础上,创新性地提出了并联混合直流输电系统无功协调控制策略。首先分别研究换流站慢速无功控制和柔性直流单元快速无功控制;继而针对常规直流馈入弱交流系统存在的电压不稳定问题,提出一种换流站无功补偿装置与柔性直流单元的无功协调控制策略;最后基于PSCAD/EMTDC仿真平台,搭建并联混合交直流仿真系统,分别就稳态及暂态情况下的无功协调控制策略进行仿真分析。分析结果表明,无功协调控制策略稳态时能够抑制换流母线电压波动,受端电网故障时能够抑制常规直流单元换相失败,提高其故障恢复能力。论证了并联混合直流系统无功协调控制策略的有效性。

The hybrid parallel HVDC system adopts the parallel structure of LCC HVDC and MMC HVDC,which combines the advantages of LCC HVDC and MMC HVDC.Based on the existing reactive power control of HVDC system,the reactive power coordination control strategy of hybrid parallel HVDC system is proposed innovatively.Firstly,the reactive power control of LCC HVDC and the reactive power control of MMC HVDC are studied respectively.Then a reactive power coordinated control strategy between converter station reactive power compensation device and MMC HVDC is proposed aiming at the voltage instability when the LCC HVDC inputs to weak AC system.Finally,a hybrid parallel HVDC system is built based on the PSCAD/EMTDC simulation platform.And the reactive power coordination strategies under steady and transient conditions are respectively simulated and analyzed.The analysis results show that the reactive power coordinated control strategy can suppress the voltage fluctuation of converter bus in steady state.At the same time,the reactive power coordinated control strategy can restrain the commutation failure of LCC HVDC in the fault of receiving power grid and improve its fault recovery ability.Therefore,the effectiveness of reactive power coordinated control strategy in hybrid parallel HVDC system is demonstrated.