基于调相机与SVC协调的抑制高压直流送端风机脱网的控制策略

在大规模风电接入的高压直流送端电网中,针对发生直流故障后送端交流电压大幅波动导致的风机连锁脱网问题,探讨了直流故障导致风机连锁脱网的内在机理,分析了调相机和静止无功补偿器(SVC)在换相失败和闭锁过程中的动态无功响应特性;在此基础上,提出一种基于换流站侧调相机与风电场侧SVC协调的抑制高压直流送端风机脱网的控制策略:在换相失败和直流闭锁的不同时期,根据送端电压变化特点,分时发挥调相机自发无功响应能力、励磁控制能力和SVC无功调节能力,以抑制暂态压降或暂态压升的幅度超过风机脱网的保护阈值.最后,通过对测试系统和实际电网的仿真,验证了所提控制策略可有效抑制直流故障后送端暂态电压变化,降低风机连锁脱网的风险.

Control strategy of suppressing wind turbine tripping based on coordination between synchronous condenser and SVC in sending-end network of HVDC

In the sending-end network of HVDC(High Voltage Direct Current) connected with large-scale wind power, aiming at the wind turbine cascading tripping caused by large fluctuation of AC voltage at the sending-end network after DC fault, the internal mechanism of wind turbine tripping caused by DC fault is discussed, and the dynamic reactive power response characteristics of synchronous condenser and SVC in the process of commutation failure and DC blocking are analyzed. On this basis, a control strategy of suppressing wind turbine tripping based on coordination between synchronous condenser at converter station side and SVC at wind farm side is proposed. In different periods of commutation failure and DC blocking, according to the characteristics of the voltage change of the sending-end network, the synchronous condenser abilities of spontaneous reactive power response and excitation control and the SVC ability of reactive power regulation are exerted in a time-sharing manner, so as to prevent the amplitude of transient overvoltage or transient undervoltage from exceeding the protection threshold of wind turbine tripping. Finally, through the simulation of the test system and the actual grid, it is verified that the proposed control strategy can effectively suppress the transient voltage change at the sending-end network after DC fault, and reduce the risk of wind turbine cascading tripping.