一种适用于大容量功率馈入和异步电网互联的级联换流阀

A Cascaded Converter Dedicated for Large Capacity Power Infeed and Asynchronous Interconnection

随着特高压直流输电技术的广泛应用,多回直流集中馈入带来的问题日益严重。为从换流器和电网结构两个层面有效解决多馈入直流系统的问题,该文提出一种同时具备特高压直流馈入和受端电网异步互联的级联换流阀拓扑。首先,详细介绍级联换流阀的拓扑结构及其运行特点;分析特高压级联换流阀接入对受端系统运行特性的影响。针对常规控制下级联换流阀可能出现的电压不稳定问题,提出均压附加控制策略。研究换流阀多种工作模式及工作模式间的在线切换策略,以提升系统的运行灵活性。仿真验证基于级联换流阀的直流输电系统控制策略的有效性,研究结果表明,换流阀具备直流故障清除能力和多工作模式在线切换能力;级联换流阀在多直流落点的受端电网具有较好的应用前景。

With the development of UHVDC transmission technology, the problem of multi-infeed HVDC systems become increasingly serious. To effectively solve the problem of multi-infeed HVDC system from the aspects of both converter and grid structure, a cascaded converter dedicated for UHVDC transmission and asynchronous interconnection was proposed in this paper. The topology and operating characteristics of the cascaded converter were introduced in detail. The impact of UHVDC power feeding on receiving grids was analyzed. To solve the problem of voltage instability under conventional control, the voltage balancing additional controller was proposed. Various feasible operating modes with operating switching strategies of the cascaded converter were studied to improve the operational flexibility of the system. The simulation verifies the effectiveness of the control strategy for the UHVDC system with the cascaded converter. The DC faults clearing strategy and operating modes switching strategies are verified. The analysis indicates that the cascaded converter has a good application prospect in the large capacity UHVDC system connecting to load centers.