Autonomous control of inverter-interfaced Distributed Generation units for harmonic current filtering and resonance damping in an islanded microgrid

Harmonic current filtering and resonance damping have become important concerns on the control of an islanded microgrids. To address these challenges, this paper proposes a control method of inverter-interfaced Distributed Generation (DG) units, which can autonomously share harmonic currents and resonance damping burdens. The approach employs a load compensator based on the decomposition of output current, in addition to the outer droop-based power controller, as well as inner voltage and current controllers. The load compensator consists of a virtual fundamental impedance loop for enhanced sharing of reactive power, and a variable harmonic impedance loop which allows to counteract harmonic voltage drops across the grid-side inductance of the DG inverter, and to damp the harmonic resonance propagation throughout a distribution feeder. Experiments on a three-phase microgrid are performed to validate the performance of the proposed control scheme.