基于UPFC抑制HVDC换相失败的控制方法研究

针对高压直流输电(high-voltage direct current,HVDC)系统发生换相失败的问题,运用统一潮流控制器(unified power flow controller,UPFC)减小HVDC系统发生换相失败的概率,并对UPFC的原有控制策略进行改善。当系统交流侧发生故障,UPFC并联侧控制策略采用交流侧母线电压参考值调节方法抑制换相失败的发生。引入故障水平FL来表征HVDC系统的故障严重程度,通过理论分析和PSCAD/EMTDC仿真验证:当故障水平FL为18.7%时,UPFC原有控制策略与改善后的控制策略均可抑制换相失败的发生;故障水平FL为23.1%时,只有改善后的控制策略可有效抑制换相失败的发生;故障更为严重,当故障水平达到FL为93.56%时,改善后的控制策略可有效降低连续换相失败的发生概率。运用UPFC动态无功补偿能力可增强HVDC系统受端交流系统强度,提高换相失败的抵御能力,从而有效改善了HVDC系统的运行特性。

The Control Method of HVDC Commutation Failure Based on UPFC

Aiming at the problem of commutation failure in high voltage direct current (HVDC) transmission system,the unified power flow controller (UPFC) is applied to reduce the probability of commutation failure of HVDC system,and improve the original control strategy of the unified power flow controller.When the AC side faults,UPFC shunt control strategy using AC bus voltage reference value adjustment method to suppress commutation failure.The severity of fault is introduced into the fault level FL to characterize the HVDC system,through theoretical analysis and simulation verification of PSCAD/EMTDC:When the fault level of F_L=18.7%,which can control the original control strategy and improvement strategy of UPFC inhibition after commutation failure;fault level F_L=23.1%,only the improved control strategy can effectively inhibit the occurrence of commutation failure;failure is more serious,when the fault level reached F_L=93.56%,the improved control strategy can effectively reduce the probability of occurrence of continuous commutation failure.Reactive power compensation can be affected by AC system strength enhanced HVDC system using UPFC dynamic,improve the commutation failure resistance,thereby effectively improving the operation performance of HVDC system.