Combined Frequency and Voltage Support by Wind Farm with Linear Quadratic Regulator under Converter Blocking

Abstract

When converter blocking occurs on the high voltage direct current (HVDC) transmission systems, the resulting excess active power and reactive power lead to the rise in grid frequency and bus voltage, which seriously endangers the safe operation of the power system. The traditional control methods mainly focus on the separate control of frequency and voltage, which cannot regulate them cooperatively. To address this issue, this paper proposes a combined voltage and frequency optimal control method. For the prediction of frequency and voltage, the state space models are established based on the swing equation and the voltage sensitivity matrix. Using the linear quadratic regulator (LQR), the frequency control and voltage control are inherently integrated. When blocking occurs, the grid frequency and voltage increase, and the LQR controller adjusts the wind farm's active and reactive power output to achieve a cooperative control of grid frequency and bus voltage. Simulation results verify the effectiveness of this method.