基于无功反馈控制的后续换相失败抑制方法

基于电网换相换流器的高压直流输电故障后的动态恢复过程与交直流系统间的无功交换强相关,持续的无功交换过程往往伴随着换相电压持续波动,进而可能引发后续换相失败.基于此,提出采用闭环反馈控制的无功控制方法以降低后续换相失败的风险.首先,利用实时仿真分析了采用典型低压限流(VDCOL)控制的直流系统故障恢复过程与无功交换的关系...

Suppression Method of Subsequent Commutation Failure Based on Reactive Power Feedback Control

The dynamic recovery process after line commutated converter based high voltage direct current (LCC-HVDC) transmission failure is heavily dependent on the reactive power exchange between AC and DC power grids. The continuous reactive power exchange process is often accompanied by continuous commutation voltage fluctuations, which may cause subsequent commutation failure (SCF). To deal with this issue, this paper proposes a reactive power control method using close-loop feedback control to mitigate the SCF risk. Firstly, the real-time simulation is used to analyze the relationship between the fault recovery process and the reactive power exchange for the DC system using typical voltage dependent current order limitation (VDCOL) control. Then, using the reactive power characteristic equation of the AC/DC system and the existence theorem of the implicit function, the micro-incremental relationship between the DC current and the reactive power exchange or extinction angle is analyzed, and the reactive power feedback control structure is proposed accordingly. Furthermore, a real-time DC current computation method instead of VDCOL is proposed. This method considers the two-dimensional constraints of the reactive power exchange balance and the constant extinction angle, and suppresses the interference deviation through closed-loop control to achieve higher control accuracy. Finally, the simulation results prove that the proposed method can reduce the probability of the SCF in the DC system and improve the system recovery performance.