Mode-adaptive multifunctional control of the distributed generation-based AC microgrid for seamless grid synchronisation

Abstract

This study presents a mode adaptive multifunctional control strategy that avoids the collapse of the microgrid due to the subsequent failure of the generation units and faulty grid. Its control allows the distributed generation-based AC microgrid consisting of a PV panel, wind generation unit and battery energy storage to operate seamlessly during utility connected and outage operating modes. On the occurrence/clearance of the faults, the isolation/reconnection of the microgrid to the utility is ensured via static transfer switches (STSs). The change of mode occurs between the current to voltage control or vice-versa. To ensure high-quality power in both the modes, bias compensated normalised least mean square (BC-NLMS) algorithm is implemented to estimate the total active current component of loads and to improve the power quality of the grid indices. Extended second order generalised integrator-based frequency locked loop (eSOGI-FLL) control avoids frequency and phase oscillations and provides the effective frequency and phase synchronisation. In an islanded operating mode, the enhanced proportional resonant (PR) controller along with eSOGI-FLL regulates the load voltages. The battery energy storage facilitates uninterruptable supply to the critical loads. The efficacy of the microgrid control is illustrated by the simulated as well as experimental results.