PSS design for damping of inter-area power oscillations by coherency-based equivalent model

In Japan, low-frequency oscillations have been observed on trunk transmission systems, and have been the subject for studies in fields of operation, control, and devices by many power system utilities. Power system stabilizers (PSS) are very effective controllers in enhancing the damping of low-frequency oscillations, since the controllers can increase damping torque for inter area modes by introducing additional signals into the excitation controllers already equipped with generators. To analyze and solve the problem of long-term poor damping oscillation phenomena, a method is presented to find the best allocation and to design PSS for damping inter-area power oscillations. The method is based on the single-machine-infinite-bus models derived from the multi-machine power system by coherency-based reduction technique. Dynamic simulations using a 10-machine power system model are presented in order to show the effectiveness of the PSS designed according to the proposed method.