考虑过电压抑制的特高压直流弱送端系统无功控制策略

直流闭锁等扰动引起的送端电网过电压,已成为限制直流输送能力和新能源消纳的主要约束。基于±800 k V扎鲁特—青洲(简称鲁固)特高压直流弱送端电网,结合扎鲁特换流站调相机工程和东北电网系统保护建设,提出了协调换流站滤波器(电容器)、调相机及换流站近区同步机组的过电压抑制策略。一方面,电网稳态运行时,充分利用换流站及其近区调相机和同步机组补偿阀组消耗无功,减少滤波器(电容器)的投入量,从而降低直流闭锁滤波器(电容器)滞后切除引起的暂态过电压。另一方面,调相机和同步机组无功输出增大,为抑制直流闭锁潮流大规模回退引起的稳态过电压提供了充足的回降无功备用。最后基于鲁固特高压直流送端电网验证了策略的有效性。

Reactive Power Control Strategy for UHVDC Weak Sending-end System Considering Overvoltage Suppression

The overvoltage of ultra-high voltage direct current (UHVDC) sending-end system caused by disturbances such as DC blocking has become the main constraint to the UHVDC transmission capacity and renewable energy consumption. Based on the ±800 kV Zhalute-Qingzhou UHVDC weak sending-end system and combined with the condenser project of Zhalute converter station and the system protection construction of northeast power grid in China, the paper puts forward the overvoltage suppressing strategy through coordinating converter station filters (capacitors), condensers, and the synchronous units near the converter station. On the one hand, during the steady-state operation of power grid, the converter station as well as the condensers and the synchronous units near the station is fully utilized to compensate the reactive power consumed by the valve groups, and reduces the input of filters (capacitors), thus reducing the transient overvoltage caused by the lagging removal of filters (capacitors) while DC blocking. On the other hand, the increase of the reactive power output of the condensers and the synchronous unit provides sufficient fall-back reactive power reserve for suppressing steady-state overvoltage caused by large-scale power retreat while DC blocking. Finally, the effectiveness of the strategy is verified based on the Zhalute-Qingzhou UHVDC sending-end system.