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

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 angle γ in 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.