Design of a minimum sensitivity controller for a power system under different operating conditions taking into account the effect of local load characteristics

The effect of local load characteristics on synchronous machine stability has been studied using the analytical expressions developed for damping and synchronizing torques. The inclusion of system loads may lead to instability conditions due to negative damping. Improvement of power system stability can be achieved by sending an additional signal from an optimal pole placer controller to the input of the excitation and mechanical systems of the synchronous machines. The proposed pole placer can allocate the sytem poles to desired prescribed locations while ensuring minimum sensitivity of such poles to operating condition variations over a wide range. Controller parameters are determined by minimization of an objective function using the Powell—Botm optimization routine. Time response simulations are used to illustrate the dynamic behavior of the controlled system with wide variations of operating conditions, different local load characteristics and various exciter gains.