부산대학교 도서관

Protection of the environment and the shortage of conventional fossil fuels have become the key inspirations to integrate more renewable power generators into power systems. However, high penetration of AC microgrid into the power system may increase the use of power electronic converter interface causing a decrease of overall power system inertia, reduction of available reserve power margin and growing risk of load shedding. Also, the fluctuating nature of power output from the AC microgrid due to the variable nature of power generation causes a severe burden on conventional power generators and such power deviations have a substantial impact on the system stability. This paper examines the effects of the grid-connected AC microgrid on the stability of existing power systems. Power electronics interfaced AC microgrids increase the low-frequency oscillations. To enhance the stability, a discrete mode power oscillation damping controller (PODC) is proposed for grid-connected AC microgrids. A discrete mode PODC is designed to implement the conceptual framework of periodic output feedback (POF) and various sets of input and output sampling time intervals. Both gain and optimal sampling time intervals of the POF controller are determined by utilizing the particle swarm optimization technique. In this consideration, the POF-based discrete controller is a robust power oscillation damping controller that provides distinct benefits compared to conventional power system stabilizers in the damping of low-frequency electromechanical oscillatory modes. The simulation result demonstrates the performance of discrete mode time-domain PODC with optimum control operational gain and sampling time interval under fault conditions and load perturbation.