基于特高压直流输电无功调制的直流近区交流过电压优化控制策略

The Optimized Control Strategy for AC Overvoltage of the Near Region Grid of DC Transmission System Based on Reactive Power Control in UHVDC Systems

为解决直流输电工程外送功率受阻时直流近区交流电网出现的过电压问题,提出一种基于直流无功调制的直流近区交流过电压优化控制策略。首先,对直流输电系统外送功率受阻时交流系统过电压的机理进行了研究。其次,提出了通过短时提升健全极逆变侧关断角γ从而抑制工频电压升高乃至过电压的思路。最后,提出基于发电机无功调整和直流无功调制的过电压快速优化控制策略。该策略将近区发电机和健全直流总的无功调整量最小设为目标函数建立了非线性优化模型。同时,鉴于非线性优化模型迭代次数多、求解时间长、不能满足过电压紧急在线控制的缺点,又将非线性优化模型进行了线性化,并针对西南某实际电网利用GAMS优化软件进行了对比验证。结果表明,该过电压抑制方法可以有效抑制因直流外送功率受阻后产生的过电压,同时相对于非线性优化模型,线性优化模型的求解时间大幅减少,在求解速度和控制精度上都能够满足工程实际的要求。

To solve the AC overvoltage problem of the near region grid of DC transmission system,an optimized control strategy for AC overvoltage is proposed based on DC reactive power control.Firstly,the mechanism of AC overvoltage is studied when the power transmission of HVDC is blocked.Then,the mitigating AC voltage rising or overvoltage method by increasing the extinction angleγin a short time is presented.Finally,a fast overvoltage optimized control strategy is proposed based on generator reactive power adjustment and DC reactive power control.And a nonlinear optimization model is built with the objective of minimizing reactive power amount of generator in near area and the healthy DC system.Meanwhile,due to the fact that the nonlinear optimization model has more iteration times and long solution time,which can not meet the requirement of online emergence control of overvoltage,the nonlinear optimization model is linearized.The comparison is carried out using GAMS(general algebraic modeling system)according to a southwest power grid.The comparison results show that the proposed method is able to mitigate the AC overvoltage caused by the blocked power transmission.Moreover,comparing with the nonlinear optimization model,the linear model shortens the solution time significantly and meets the requirement of the real project in solution speed and control precision.