Improved Virtual Inertia Emulation for Frequency Stability Enhancement in Microgrid System

-The increased integration of inverter-based renewable energy sources (RESs) in today's microgrids leads to many problems associated with the low inertia nature of power electronic devices that degrades the frequency response and might lead to system instability. However, virtual inertia control (VIC) is considered as one of the suitable control schemes used for controlling microgrids and maintaining the frequency stability in isolated electrical systems. This paper presents an improved technique for VIC for the battery energy storage system to enhance the frequency stability in microgrid systems under large penetration levels for RESs. The amount of emulated inertia is proportional to the rate of frequency change and the value of the VIC. Thus, in this study the developed VIC scheme uses two types of controllers, which are: the PI controller which is used for controlling the ROCOF signal and the fuzzy logic controller which is used for selecting the appropriate value of the inerta constant. Simulation and system modelling are performed using the MATLAB/Simulink software environment. The proposed scheme was tested under various operating conditions including changes in system parameters and changes in penetration levels of renewable energy resources. Further, the proposed scheme was compared with three available schemes in the literature, namely; conventional VIC, enhanced VIC with damping properties, and self-adaptive VIC, the proposed scheme shows a good improvement in the overall frequency response.