Implementation of Two-Level Coordinated Control for Seamless Transfer in Standalone Microgrid

This article presents control strategies developed with two-level coordinated and double loop control for a standalone microgrid. The interfacing inverter is controlled to perform multifunctions. It incorporates the compensation for power quality problems at the point of common coupling and controls the voltage and frequency deviation to provide a constant voltage and frequency to connected ac loads in standalone and grid-connected operating modes. The power demand during battery charging and discharging is controlled using a buck–boost converter. To control overshoot and settling time while following a dc and sinusoidal references without losing control during the transition, proportional-integral, and proportional-resonant controllers with optimal gain designs are reinforced by antiwindup feedback. To ensure a soft and secure transition, even under disturbances, such as distortions and notches, an enhanced phase-locked loop is used. The performance of this system is simulated in MATLAB and validated on a 2-kW laboratory prototype.