Robust control design in AC/DC system

This paper demonstrates how to design an H_∞ based damping controller for an HVDC link to enhance system damping under different operating conditions. Numerator-denominator perturbation representation is used to represent the model uncertainty and the partial pole placement technique is employed to assign the critical mode to a specified location. A robust H_∞ controller is successfully designed by treating the change of operating conditions of the highly nonlinear power system as model uncertainty. Simulation results show that the proposed controller is very effective to enhance the performance and robustness of the power system under the predefined uncertainties.