Comparative Analysis of Self-Synchronized Virtual Synchronous Generator Control and Droop Control for Inverters in Islanded Microgrid

Due to increased penetration of inverter based distributed generators (DGs) in power system, conventional control methods fails to maintain grid stability, flexibility, and scalability. The inherent problem with DGa is the heavy use of power electronic devices with in the realm of inverters. These inverters have been modeled as have been controlled as current source, and voltage source in accordance with control strategy employed. However there is one control mode of operation under which the voltage and current source inverters fail which entails utilization of control scheme that mimic the synchronous generator operation. Synchronous generators have excitation and speed governor controls that allows grid supporting mode of operation as well as smooth transition from grid connected to islanded modes. The inverters can be controlled to behave as virtual synchronous generators (VSGs) to capture all the inherent inertia and damping that is required for maintaining grid voltage and frequency stability thus providing a flexible control. In this paper, we have modeled VSG. The simulation dynamic responses using MATLAB/SIMULINK under multiple connected loads and different operating scenarios is presented in this paper and analyzed. In addition, load sharing characteristic of VSG based and droop based inverters is compared.