Mountain gazelle optimisation-based 3DOF-FOPID-virtual inertia controller for frequency control of low inertia microgrid

The primary objective of the authors is to design a new robust and improved virtual inertia controller (VIC) for renewable energy dominated inverter interfaced low inertia microgrid (LIMG). Increasing penetration of inertia-less renewable generation in microgrid leads to increased frequency deviation during and after a disturbance. To improve the frequency response of the LIMG, conventional VIC added with different second stage and third stage controllers are proposed in existing works. Higher degree-of-freedom (DOF) PID controller synchronised with fractional-order (FO) operators are used with conventional VIC controllers. These controllers work in addition with conventional VIC and the multi-stage controllers make the system more complex. To reduce the number of controller stages and, subsequently, reduce cost and complexity of the system, a single stage 3DOF-FOPID controller is proposed to mitigate the frequency deviation after a disturbance in a LIMG. Performance of the proposed single stage controller is compared with that of the existing controllers to establish the advantages of the proposed controller. The parameters of the proposed 3DOF-FOPID controller are optimised by Mountain Gazelle Optimsation. The robustness of this controller is also tested for random load fluctuation and renewable power variations in presence of system non-linearities.