背靠背混合直流的无功协调控制策略研究

Research on Reactive Power Coordination Control Strategy for Back to Back Hybrid-HVDC System

常规直流的低负荷无功控制功能会使常规直流运行在较大的触发角或关断角状态下,从而造成换流阀应力增大,损耗增加;常规直流的关断角备用控制功能会造成常规直流系统状态的改变,引起功率波动。为了降低上述负面影响,以云南异步联网工程为背景提出了一种适用于背靠背混合直流输电系统的无功协调控制策略。该策略针对传统直流在低负荷运行及交流滤波器投切瞬间2种无功工况下,利用柔性直流输电精准快速的无功调节能力,优化混合直流的无功特性,达到平衡系统无功,改善系统运行动态特性的目的。最后在PSCAD/EMTDC环境中搭建了云南异步联网工程的电磁暂态模型,仿真验证了所提控制策略的有效性。

Low-load reactive power control function of conventional HVDC creates large firing angle or extinction angle of HVDC converter, which increases converter valve stress and power losses. Extinction angle backup control function of LCC-HVDC also leads to system status change and induce power fluctuations. In order to reduce those negative impacts, a reactive power coordinated control strategy for back to back hybrid-HVDC system based on Yunnan asynchronous intereonnection project, using fast and precise reactive power control ability of MMC, is proposed. A electromagnetic transient model of Yunnan asynchronous interconnection project is build in PSCAD / EMTDC to verify effectiveness of proposed control strategy.