适用于大规模风电并网的多端柔性直流输电系统控制策略

提出了一种适用于区域大规模风电并网的六端柔性直流输电系统,设计了该系统的协调控制策略,即送端电压源型换流器(VSC)采用交流电压控制、受端VSC采用直流电压下垂控制。以直流网络损耗最小作为优化目标,计算了系统稳态运行点。通过在PSCAD/EMTDC平台上搭建仿真算例,验证了所提出的系统控制策略可以自动跟踪风电功率波动并协调受端功率分配。通过设计系统启动和风功率波动及交流侧故障和换流器停运的仿真算例,验证了该六端柔性直流输电系统具有良好的功率调控能力和运行灵活性。

A Multi-terminal VSC-HVDC System Control Strategy for Large Wind Farms Integration

A six-terminal voltage source converter (VSC) based HVDC (VSC-HVDC) system is proposed for connecting large wind farms to the main AC grid. A coordinated system control scheme is also presented, i.e., the sending side VSC is AC voltage controlled while the receiving side VSC is DC voltage droop controlled. It can ensure smooth system operation and proper power sharing among different receiving end grids. Simulation results using PSCAD/EMTDC demonstrate its satisfactory performance and flexible operation of the proposed VSC-HVDC system and control strategy under different conditions, including start-up, wind power variation, AC grid short circuit fault and large disturbances caused by the trip of one sending side VSC or one receiving side VSC. This work is supported by the Funds for International Cooperation and Exchange of the National Natural Science Foundation of China (No. 51261130484), National High Technology Research and Development Program of China (863 Program) (No. 2011AA05A112) and State Grid Corporation of China (No. 2013-304).