| In conventional centralized power systems, power is generated mostly by large synchronous generators (SGs), where the frequency of the grid depends on the rotational frequency of the prime mover. If there are any sudden changes in the load, the rotor inertia property restrains the changes in frequency and keeps the system stable. During transient periods, rotor kinetic energy of the rotor is injected into the grid to balance power supply between generation and load. With the recent high penetration of renewable energy sources (RES), the power grid is undergoing structural changes with an increased inverter-based distributed generation. Since inverter based power sources do not have inertia as conventional synchronous machines (SM), high penetration of inverters may cause instability and sharp voltage fluctuations in the grid. If inverter based power sources could be configured as regular SM by introducing virtual inertia and damping property, many of the problems, such as frequency regulation, islanded operation, and parallel operation of inverter-based DGs will be resolved. This thesis investigates mathematical modeling and control of VSG's to emulate the inertia and damping property of SMs. Simulation results are presented on the modeling and closed-loop performance of VSGs for an island microgrid. |
