An Optimal Frequency Control Method of Asynchronous Power Grid Considering Multi-HVDC Emergency Power Support

Emergency DC power support has become an effective frequency stability control approach. For the asynchronous power grid with multi-HVDC links, this paper proposes an optimal control based on wide-area measurements (WAMS). The prominent advantage of this control is to improve the frequency stability of the disturbed grid while taking into account the influence on power flow, node voltage and other grid frequency fluctuations. In order to evaluate the post-disturbance frequency stability, a steady-state frequency prediction model based on WAMS data is first proposed, which can reflect the correspondence between post-disturbance steady-state frequency and the DC power support amount. In order to obtain the optimal control strategy, an optimization model is established to formulate the proposed control problem. The optimization objective of the model is to minimize the frequency deviation of interconnected power grids, and the constraints are to restore steady-state frequency to target value and ensure the security of line power flow and node voltage. The final control strategy is obtained by solving the optimization model. Simulations of the modified IEEE 50-generator system are performed to validate the accuracy of the proposed frequency prediction model and the effectiveness of the proposed frequency stability control.