多馈入直流输电系统后续换相失败安全裕度评估及抑制方法

Safety Margin Assessment and Suppression Method for Subsequent Commutation Failure in Multi-infeed LCC-HVDC Systems

换相失败可能引起直流输电系统(line commutated converter based high voltage direct current,LCC-HVDC)闭锁,严重影响电网的安全稳定运行。多馈入直流输电系统中电气耦合紧密,控制响应造成多回LCC-HVDC交互影响,使换相失败的产生机理变得更加复杂。现有后续换相失败抑制方法多以单回LCC-HVDC为对象,无法兼顾自身换相恢复和相邻直流换相失败抑制的需求。为此,提出了一种适应于多馈入直流输电系统的后续换相失败抑制方法。分析了LCC-HVDC首次换相失败恢复过程中逆变站控制系统的响应时序及条件,提出了考虑故障严重程度和LCC-HVDC控制影响的后续换相失败安全裕度评估方法,进而提出了基于电压安全裕度的后续换相失败抑制方法,并在CIGRE HVDC标准测试系统验证了所提方法的有效性。仿真结果表明,所提方法根据换流母线电压自适应地调节直流电流,能够有效降低多馈入直流输电系统中无功电压耦合影响,有效抑制相邻回LCC-HVDC发生后续换相失败。

Commutation failure may cause the blocking of line commutated converter based high voltage direct current(LCC-HVDC)system,which seriously affects the safe and stable operation of the power system.The tight electrical cou-pling in multi-infeed LCC-HVDC systems and the control response cause multiple LCC-HVDC interactions,making the mechanism of commutation failure more complex.The existing suppression methods of subsequent commutation failure are mostly targeted at single LCC-HVDC,which cannot take into account the needs of the own commutation recovery and suppression of commutation failure of adjacent LCC-HVDC.Therefore,a suppression method for subsequent com-mutation failure adapted to multi-infeed LCC-HVDC systems is proposed in this paper.The response timing and conditions of the inverter station control system during the recovery of the first commutation failure of LCC-HVDC are analyzed,and the safety margin assessment method of the subsequent commutation failure considering the fault severity and the control impact of LCC-HVDC is proposed.The suppression method for subsequent commutation failure based on the voltage safety margin is further proposed,and the effectiveness of the proposed method is verified in the CIGRE HVDC standard system.The simulation results show that the proposed method can be adopted to effectively reduce the coupling ef-fect of reactive power and voltage in multi-infeed LCC-HVDC systems,and to suppress the subsequent commutation failure of adjacent LCC-HVDC by adaptively adjusting the DC current according to the voltage of the converter bus.