Frequency response improvement in microgrid using optimized VSG control

In the recent years, the disadvantages of the inverter based distributed energy resource, such as less inertia and lower available kinetic energy as compared to synchronous generator (SG), have been addressed by researchers. As a result, the virtual synchronous generator (VSG) or virtual synchronous machine (VSM) is suggested in literature. VSG controller allows the inverter to mimic the characteristic of the synchronous generator by emulating the swing equation of SG. In case of VSG control, one can change the parameters of swing equation in real-time to improve the transient response of the system, which is not possible in an actual synchronous machine. Based on this concept, an optimized VSG control is discussed in this paper, in which the inertia constant and damping factor are altered between two values based on relative virtual angular velocity and its rate of change. The optimized values of virtual inertia constant and virtual damping factor are obtained, by formulating, aggregated fitness function of frequency deviation and voltage deviation. Particle Swarm Optimization (PSO) technique is used to minimize the function. Lyapunov direct method is used for the transient stability analysis of the system.