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 stabil ity has been studied using the analytical expressions developed for da mping and synchronizing torques. The inclusion of system loads may lea d to instability conditions due to negative damping. improvement of po wer system stability can be achieved by sending an additional signal f rom an optimal pole placer controller to the input of the excitation a nd mechanical systems of the synchronous machines. The proposed pole p lacer can allocate the sytem poles to desired prescribed locations whi le ensuring minimum sensitivity of such poles to operating condition v ariations over a wide range. Controller parameters are determined by m inimization of an objective function using the Powell-Botm optimizatio n routine. Time response simulations are used to illustrate the dynami c behavior of the controlled system with wide variations of operating conditions, different local load characteristics and various exciter g ains.