A proportional harmonic power sharing scheme for hierarchical controlled microgrids considering unequal feeder impedances and nonlinear loads

This paper presents a proportional harmonic power sharing (PHPS) control scheme to improve the voltage quality at point of common coupling (PCC) and share harmonic power simultaneously for an islanded microgrid. The proposed control strategy employs P+ multiple resonant controller, and P⁺ plus Q⁺-based improved droop control scheme to improve the voltage quality at the load bus. Additionally, the second-order generalized integrators (SOGI) filtering model-based virtual harmonic impedance is utilized to minimize the influence of an islanded microgrid under mismatched line impedance and nonlinear load distribution conditions. Furthermore, the hierarchical harmonic power controller is used to share the individual harmonic powers proportionally, and the circulating currents can also be significantly decreased. Finally, the simulation results are provided to validate the effectiveness of the proposed PHPS control scheme for islanded microgrids under unequal feeder impedance and nonlinear loads conditions.