直流闭锁后风电送端系统暂态稳定及控制策略研究

Study on the Transient Stability and Control Schemes of the Sending-End System Involving Wind Power after UHVDC Block

直流闭锁会严重冲击大规模风电特高压交直流外送系统(WIND-UHVDC/AC)送端暂态稳定性。为提升送端系统暂态稳定性,首先推导了风电外送系统送端同步机电磁功率解析表达式,基于等面积准则(EAC)分析了直流闭锁后双馈风电机组(DFIG)功率速降对系统功角稳定性影响的影响机理,提出了风电功率速降控制策略;其次,基于直流闭锁及切除电容器对系统暂态电压特性影响机理的分析,提出闭锁后保留部分整流站电容器的控制策略,以提升交流外送线路暂态电压稳定,并分析了电容器切除延时变化对系统功角稳定性的影响;最后,通过西北电网实际风电外送系统仿真和对比,验证了直流闭锁后风电功率速降能够提升送端功角稳定性,保留整流站部分电容器能够提升交流外送线路暂态电压稳定,且对送端系统功角稳定性影响较小。

Ultra-high voltage direct current(UHVDC)block will seriously impact the transient stability of the sending-end system of wind power transmitted by mixed UHVDC/ultra-high voltage alternating current(UHVAC)system(WIND-UHVDC/AC system).To improve the transient stability of the sending-end system,the equation of electrical power of the synchronous generator(SG)in the sending-end system was deducted firstly,the impact of active power fast reduction of double fed induction generator(DFIG)after UHVDC block on the rotor angle stability was analyzed based on the equal-area criterion(EAC),and the control scheme of the active power fast reduction of DFIG was proposed.Then,based on the analysis of UHVDC block and capacitors switch-off on the transient voltage characteristics,the control scheme of reserving partial capacitors after UHVDC block to improve the transient voltage stability of UHVAC lines was proposed.Besides,the impact of variation in the capacitors switch-off time delay on the rotor angle stability was analyzed.Finally,the simulation results of the actual WIND-UHVDC/AC system in China’s northwest power grid show that active power fast reduction of DFIG can improve the rotor angle stability,reserve capacitors can improve the transient voltage stability of the UHVAC lines and has little impact on the rotor angle stability.