特高压混合级联多端直流输电系统的协调控制策略研究

逆变侧采用电网换相换流器(LCC)和模块化多电平换流器(MMC)串联组成的特高压混合级联多端直流输电系统,为特高压直流输电提供了一种更为经济、灵活、快捷的输电方式。基于现有直流电网的协调控制策略,文中对受端MMC阀组之间的协调控制策略进行了深入的分析研究,并考虑了5种协调控制策略。然后,在PSCAD/EMTDC中,对上述5种策略遭受不同故障的响应特性分别进行仿真,故障包括送端交流故障、直流线路故障、受端LCC交流故障、受端MMC1交流故障及MMC1紧急闭锁退出。最后,基于仿真结果,对上述5种协调控制策略的适用性进行了对比分析。仿真结果表明:策略1和策略3遭受各种故障均能有效穿越;策略2、策略4和策略5在遭受直流线路故障时均发生不同程度的功率倒转,需要采取措施抑制。

Coordinated control strategy for hybrid cascaded UHVDC system

The hybrid cascaded ultra-high voltage direct current (UHVDC) system of line-commutated converter (LCC) and modular multilevel converter (MMC) in series at receiving end provides a more economical, flexible and fast transmission mode for UHVDC transmission. Based on the existing coordinated control strategy of DC power grid, the coordinated control strategy among MMC valve groups is analyzed and studied, and five coordinated control strategies are considered. Then, with PSCAD/EMTDC, the response characteristics of the above five strategies subjected to different faults are simulated respectively, including sending-end AC fault, DC line fault, receiving-end LCC AC fault, receiving-end MMC1 AC fault and MMC1 immediately shutdown and exit. Finally, based on the simulation results, the applicability of the above five coordinated control strategies is compared and analyzed. The simulation results show that strategy 1 and strategy 3 ride through effectively under various faults. Strategies 2, 4, and 5 suffer from different degrees of power reversal under DC line fault, and the measures should be taken to restrain the power reversal.