Research On Robust Control Strategies For VSC-HVDC

With the development of high-power power electronic elements and PWM technique, VSC-HVDC has more and more attention and has been successfully used in actual power system. VSC-HVDC has many advantages, for example, it can reverse the direction power flow flexibly, obtain the individual control of active power and reactive power, supply the power to passive network and etc. It has important practical significance to strengthen research on the subject of VSC-HVDC. The robust control strategies for VSC-HVDC are mainly studied in considering the uncertainty in the model, the controller parameters perturbation and the external interference in this paper.This paper analyzes the block diagram of voltage source converter of VSC-HVDC system firstly, and then establishes the state space equations for the controlled object in the dqO coordinate system in considering model parameters uncertainty. The paper designs state-feedback robust H∞controller for the uncertainty model by applying LMI(Linear Matrix Inequality) technology, and then designs robust H∞controllers for rectifying side and inversion side of the transmission system respectively. On that basis, the author focuses on that the controllers often exist parameters perturbation in the practical engineering application, and then designs robust non-fragile H∞controllers by applying LMI technology for rectifying side and inversion side of the transmission system respectively. At last, the Matlab simulation demonstrates that the proposed controllers poss good robust performance and non-fragile performance.This paper also analyzes the block diagram of VSC-HVDC transmission system, and establishes the nonlinear uncertainty system model of the transmission system in the dqO coordinate system in considering external disturbance. The paper turns the nonlinear model into the linear model in new coordinate system by exact linearization, then gets the control law of the linear model by H∞control theory, and then designs H∞controllers for rectifying side and inversion side of the transmission system respectively. At last, the Matlab simulation demonstrates the proposed controllers poss effective performance and good robust performance.