Modified VSG Scheme for Secondary Frequency Regulation in Islanded Microgrid

The traditional control strategy of a microgrid in islanded mode mainly consisted of Droop control. To improve it Virtual Synchronous Generator (VSG) concept was developed. The objective of the method was to improve the frequency response of a system following a sudden disturbance. Though these traditional control strategies are successful in providing primary frequency response (PFR) and inertial response (IR), the frequency restoration process is overlooked. The proposed method introduces two PI controllers in the active power-frequency loop of VSG by which the system frequency returns attains the nominal value in a quick time after the disturbance. The process is called secondary frequency regulation (SFR) and the proposed controller is called modified VSG as it uses the same set of control models as used in VSG. This work focuses on the comparison of traditional and proposed controllers in providing the three responses namely IR, PFR, and SFR. The controller performance is validated using MATLAB Simulation.