LOC-PSS Design for Improved Power System Stabilizer

Document Type : Original Article


Department of Electrical Engineering, Gorgan Branch, Islamic Azad ‎University, Gorgan, Iran‎


A power system stabilizer (PSS) is an ancillary device used for improving stability of otherwise poorly stable power system. It helps to restore the system back to the operating point after disturbances like load changes or faulty situations are withdrawn or smoother transition from one to another operating point. Originally, power system stabilizers are installed to add damping to local oscillatory modes, which were destabilized by high gain, fast acting exciters. Its property is to provide damping torque to reduce the electromechanical oscillations introduced in the system under disturbances. In this paper, first, we analyze different types of small signal stabilities of a power system using linearized model and then, design a stabilizer for Single Machine Infinite Bus (SMIB) system. A comparison between the effect of Linear Optimal Control plus PSS (LOC-PSS) and Conventional PSS(CPSS) in terms of either power system responses or its eigen-values due to different load condition is reported. Simulation results show the LOC- PSS is robust for such nonlinear dynamic system and achieves better performance than the CPSS in damping oscillations. The effectiveness of the PSS for different load disturbances is illustrated with simulation carried out in MATLAB software.