Power quality improvement and seamless transfer in a grid-connected microgrid system using <i>H</i><SUB align="right">∞ controller

In this paper, an H∞ controller-based cascaded control strategy has been discussed and analysed for the improvement of power quality and smooth seamless transition between the operating modes in a grid-connected microgrid system. The control strategy involves two control loops namely, an outer grid current control loop and an inner local load voltage control loop. Both the control loops are designed using H∞ repetitive controllers. Particle swarm optimisation (PSO) technique is used to optimise the weighting parameters of the H∞ controller to design an optimal controller for achieving the desired performance. The main objective of the control strategy is to minimise the harmonic content present in the load voltage and the grid current ensuring smooth transition between the operating modes of the microgrid without any noticeable transients. The H∞ repetitive controller with optimised weighting parameters outperforms the other traditional controllers in achieving better dynamic response with reduced THD.