换相失败下直流送端SVC无功反调机理分析及控制策略研究

Mechanism analysis and control strategy research of SVC reactive power inversion of DC transmission system due to commutation failure

直流送端系统配置的动态无功补偿设备存在无功反调特性,换相失败情况下该特性会助增直流送端的交流系统出现暂态过电压。文中对直流送端系统暂态电压进行频谱分析,得到其谐波主导频率,并对SVC控制系统进行相频特性分析,揭示了SVC发生无功反调的内在机理,即SVC滞后特性是其在换相失败时发生无功反调的根本原因。并在此基础上提出了SVC电容器投切控制策略,通过在电压恢复阶段切除部分电容器,有效抑制了SVC无功反调现象,仿真验证了SVC控制策略的有效性。

The DC transmission system equipped with dynamic reactive power compensation devices has reactive power inversion characteristics, which could contribute to the transient overvoltage of the AC system when commutation failure happens. Firstly, the transient voltage of the DC transmission system is spectrally analyzed and its harmonic dominant frequencies are acquired. Secondly, the phase frequency characteristics of the SVC control system are analyzed, which reveals the internal mechanism of SVC hysteresis properties. The SVC hysteresis characteristic is the root cause of SVC reactive power inversion when commutation failure happens. On this basis, the control strategy for SVC capacitor switching is proposed. Part of the capacitors is removed during the recovery of the voltage, thus effectively suppressing the SVC reactive power inversion. Finally, the simulation results verify the effectiveness of the SVC control strategy.