风电–多端柔直送出系统电压源型控制

Voltage Source Control of VSC-MTDC Systems With Wind Farm Integration

为解决风电–多端直流送出系统并网带来的惯量缺失及稳定性问题,该文提出一种适用于受端换流站的电压源型控制策略。在受端换流站利用直流母线等效电容固有动态特性实现无锁相环自主电网同步控制,使受端换流站对交流电网体现为电压源,解决并入弱电网的谐振问题;并在直流侧附加虚拟电阻,使直流侧体现为下垂特性,以协调多受端换流站间的功率分配。此外,受端换流站直流侧电压还能自主响应电网频率变化,自动调节直流系统潮流,从风场或其他电网调用功率,为出现频率偏差的电网提供频率支撑。最后通过PSCAD/EMTDC仿真软件构建四端直流系统仿真算例,验证所提控制方法的有效性。

In order to solve the problem of inertia loss and stability issues brought by grid integration of wind power with multi-terminal DC systems,this paper proposed a novel control strategy for voltage source converter based high voltage direct current(VSC-HVDC)systems.By utilizing the nature response of the DC side equivalent capacitor,self-synchronization could be realized in receiving end converters(RECs).The REC station is embodied as a voltage source to the AC grid,which solves the resonance problem of the weak grid.Virtual resistance is attached to realize droop characteristics at DC side,which can coordinate power allocation among multiple RECs.In addition,the DC bus voltage can respond to grid frequency changes autonomously,and adjust the power allocation to provide frequency support to power grids.Finally,a four-terminal HVDC transmission system with wind farm integration has been modeled in PSCAD/EMTDC wherein the effectiveness of proposed control strategy has been verified.