State space modelling and seamless transition between Islanded and Grid-connected operation modes

Three Voltage Source Inverter (VSI) based distributed renewable sources are considered in a microgrid (MG). This research is important for developing more reliable and resilient power systems, specifically by investigating the transient behaviour of VSI frequency and voltage under sudden changes, to ensure an uninterruptible supply of power to critical loads. A smooth transfer from islanded (IS) mode to grid-connected (GC) mode is necessary to provide higher reliability when excess power is needed in the isolated network or vice versa. The key objective of this research is to evaluate how sudden load fluctuations at particular distributed generation (DG) units affect the MG when it’s operating in IS mode. To accomplish this, we introduce a state-space model for analyzing MG stability. We also investigate the transition from IS mode to GC mode to ensure a smooth and stable progression. This modelling approach significantly enhances the practical reliability and efficiency of MGs. The case study has been realized through implementation in the MATLAB/SIMULINK with m-file to observe the MG and grid stability under transient conditions.