H∞ robust control of direct-drive permanent magnetic synchronous generator considering the uncertainty of stator parameters

The robust control issues of direct-drive permanent magnet synchronous generator (DD-PMSG) are discussed, in which the variation of stator resistances and inductance are considered. The speed loop of DD-PMSG is a linear system with several ways of disturbance inputs, so the H_∞ mixed sensitivity control method is applied to eliminate the torque disturbance and measurement noise. The current loop is regarded as an uncertain DESCRIPTOR system and the output-feedback H_∞ robust control algorithm for the uncertain DESCRIPTOR system is proposed. Linear matrix inequalities (LMI) is adopted to prove the sufficient conditions of descriptor system quadratic stability and satisfying the H_∞ robust performances, and then an output feedback controller is presented. Simulation results show that comparing with PI controller and the standard H_∞ method designed controller, the proposed controller has better response and control accuracy, the inhibition of disturbance input and parameter uncertainty has better robustness than the PI controller, and less conservative than the standard H_∞ controller.