tThis paper addresses the problem of determining robust three-term output-feedback power system sta-bilizers (PSSs) (C1(s) = (x1s + x2+ x3/s) ; C2(s) = x1(1 + x2s)/(1 + x3s)) which can function properly over widerange of operating conditions. Necessary and sufficient constraints that characterize the admissible setof PSSs parameters are derived firstly by applying Routh-Hurwitz (RH) criterion to the characteristicpolynomial of the generalized plant model. The complete set of stabilizing PSSs for any operating point istherefore determined in the controller parameter space [x1, x2, x3] by plotting RH constraints at this point.Since the design parameters are load-dependent and have to be adjusted at each operating condition,an interval plant is developed to describe uncertainties in the model parameters imposed by continuousvariation in load patterns. Necessary and sufficient constraints for Hurwitz stability of such interval plantare derived using Kharitonov’s theorem where robust PSS design is reduced to simultaneous stabiliza-tion of finite number of vertex/segment plants. The stability region for each of these plants is plottedusing RH constraints where the intersection of the resulting stability regions yields the set of parametersthat guarantee Hurwitz stability of the considered interval plant. Simulation results of an applicant PSS confirm the effectiveness of the proposed design approach. |
