Study and Improvement of AC Microgrid Stability Using GSA

The operation of a microgrid poses stability challenges in grid connected as well as in islanded mode of operation. Small disturbances such as sudden load change which occurs during normal operation causes transient oscillations, which deteriorate the performance of the system. The paper presents the modelling of voltage source inverter based distributed generator which consists of power controller, voltage controller, current controller and LC filter with coupling inductor. The linearized model of the microgrid is obtained to analyse the small signal stability of the system using eigenvalue analysis. The eigenvalue analysis of the system determines dominant parameters subjected to system stability and their optimum value using root locus method. A gravitational search algorithm is implemented to evaluate the optimum value of dominant parameters in order to enhance system dynamic performance. The proposed algorithm is validated on a two inverter based test system under various operating conditions including change of mode of operation, three phase fault and load changes during islanded mode of operation. Simulation results show the effectiveness of the proposed algorithm which results in enhanced dynamic performance of the system with reduced overshoot and settling time.