VSC- MTDC输电系统的新型混合式控制策略

以提高电压源型多端直流输电（VSC-MTDC）的运行可靠性为目的,针对VSC-MTDC输电系统现有控制策略存在的问题,提出了一种基于VSC-MTDC输电系统主、从式控制和电压下降式控制的新型混合式控制策略,并根据控制策略设计了相应的VSC控制器。该控制策略可以根据系统扰动的大小,使输电系统在主、从式控制和电压下降式控制中自由切换,最大限度地保持系统的稳定运行。采用在PSCAD/EMTDC中搭建的基于电压源型换流器四端直流输电系统仿真模型,对所提出的控制策略进行了仿真验证,仿真结果表明：直流输电系统能够自动进行均流且不失稳定性;每个换流器可以独立调节向直流网络输送的直流功率;新型控制方案确实可行。

A Novel Hybrid Control Strategy for VSC-MTDC Transmission System

To improve the operation reliability of VSC-MTDC system, a novel hybrid control strategy based on principal and subordinate control and voltage drop control was presented, on which the corresponding controller of VSC was designed to switch the transmission system freely according to system disturbance strength. Finally, a four-terminal VSC-MTDC model was developed in PSCAD/EMTDC to validate the feasibility of the proposed control strategy. The simulation results prove that the system is able to maintain the desired power distribution automatically without losing the stability and each converter can independently regulate DC power transferred to DC network, which shows the feasibility of novel hybrid control strategy.