Robust power system stabiliser

Power system stabilisers (PSS) are usually implemented by feeding a speed s ignal through a supplementary loop that comprises a proper phase lead. The design parameters of this loop are load dependent. Thus, they have to be ad justed at each operating condition. A simple robust PSS is designed that ca n properly function over a wide range of operating conditions and extend th e machine loadability. The lead compensator design is achieved by drawing t he root loci for a finite number of extreme characteristic polynomials. Suc h polynomials are obtained, using the Kharitonov theorem, to reflect wide l oading conditions on characteristic equation coefficients. For this purpose the explicit analytical forms for the coefficients of the system transfer functions are derived. Simulation results illustrate the effectiveness of t he proposed stabiliser as it is applied to the original nonlinear different ial equations describing system dynamics under wide loading conditions at l agging and leading power factors.