Robust output feedback power system stabilizer design: an LMI approach

Design of output feedback power system stabilizers (PSSs) that guarantee robust pole clustering and robust performance for a wide range of loading conditions is described in this paper. The objectives considered are clustering the closed loop poles in a prescribed region in the s-plane while minimizing an H_infin performance criterion for the uncertain system. The main difficulty in PSS design is that power systems encounter continuous variations in the load patterns and consequently the nominal model design does not guarantee satisfactory performance at other operating conditions. To cope with such variations, a systematic approach is proposed to present the plant uncertainty in the form of a polytopic model. Based on this model, the synthesis of output feedback PSS leads to a bilinear matrix inequality (BMI) optimization problem. A fast LMI-based procedure for computing an initially feasible controller is presented and an iterative LMI algorithm is suggested to solve the BMI optimization problem. Simulation results on a single machine infinite-bus nonlinear model illustrate the validity of the proposed design procedure.