Multimode control strategy to improve the power quality and autonomy of PV-Wind-BESS based microgrid using harmonic frequency adaptive observer filter

This article proposes a multifunctional control scheme to enhance the mode adaptive capability that prevents the collapse of microgrids subsequent to the failure of the utility grid and power generation units. The proposed control scheme allows photovoltaic, wind, and battery energy storage-based microgrids to operate impeccably during grid-connected and islanding modes. Static transfer switches are used to isolate and relink the microgrid to the utility on occurrence and clearing of faults. However, due to the presence of harmonics of variable frequencies in the utility grid, the mode transfer fails using conventional schemes. To the contrary, a novel harmonic frequency adaptive observer (HFAO) filter is proposed in this paper for accurate tracking of harmonic frequencies to exact fundamental components of signals under inadequate grid and nonlinear load conditions. The HFAO calculates frequencies and magnitudes of harmonics present in the signal accurately with reduced ripples, increases the robustness of quadrature-phase signal to sub-harmonics, and improves harmonic rejection property. All conceivable implications of the proposed controller are investigated under various conditions of load and microgrid operating modes using MATLAB®/Simulink® environment. Results from in-silico experiments confirm that compared to conventional control schemes, the proposed controller is more accurate in tracking harmonic frequency signals with respect to changes in grid distortions and loads.