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高压直流输电(high voltage direct current,HVDC)由于快速响应和短时过载特性对紧急控制或功率突然严重缺额地区进行紧急功率支援作用巨大,同时能很好解决区域振荡问题。利用PSCAD/EMTDC建立3机3直流系统的仿真模型,然后,在不添加任何直流附加控制的情况下,分别对正常运行的HVDC1、HVDC2和HVDC3的控制系统施加与功率增量P对应的调制指令,利用Prony辨识分析发电机功角差,找出有效抑制交流系统振荡的直流控制点。并根据最优变目标理论,在HVDC1停运时以最大能量耗散原理为基础利用故障驱动和轨迹驱动分时段进行紧急控制和阻尼控制,研究大扰动后交直流系统恢复稳定情况。结果表明利用分时段紧急协调控制且只在有效控制点进行后时段(即第2和第3时段)直流小方式调制能有效提高系统暂态稳定,改善系统后续阻尼,防止过/欠控及后续摆阻尼降低现象发生,使系统快速恢复稳定。
Due to the rapid response and short-time overload characteristics, the HVDC (HVDC) has a great effect on emergency power support for emergency control or sudden shortage of power, and can solve the regional oscillation problem well. Using PSCAD / EMTDC, the simulation model of 3-DC system is established. Then, without adding any DC additional control, the modulation commands corresponding to power increment P are respectively applied to the control systems of HVDC1, HVDC2 and HVDC3 in normal operation , The power angle difference of generator is analyzed by Prony identification to find the DC control point which can effectively suppress the oscillation of AC system. According to the theory of optimal variable target, based on the principle of maximum energy dissipation during the shutdown of HVDC1, emergency control and damping control are conducted by using fault driven and trajectory-driven sub-periods to study the recovery of AC-DC system after large disturbance. The results show that the DC mode modulation can effectively improve the system transient stability and improve the system’s subsequent damping, prevent over / under control and follow-up only by using the sub-period emergency coordination control and only after the effective control point is in the period of time (ie, the second and third periods) Pendulum damping reduces the phenomenon, the system quickly restore stability.