A unified selective harmonic compensation strategy using DG-interfacing inverter in both grid-connected and islanded microgrid

This paper presents a unified selective harmonic compensation strategy using DG-interfacing inverter with LCL filter in the presence of nonlinear local loads for both grid-connected and islanded microgrid. Compared with the existing harmonic compensation methods in the literature, the proposed strategy consists of a triple-control-loop in the grid-connected mode to compensate the grid current harmonics and a double-control-loop in the islanded mode to compensate the supply voltage harmonics at the Point of Common Coupling (PCC). Moreover, the triple-loop can be transferred to double-loop seamlessly without additional mode selection algorithm when mode transfer is needed. Furthermore, a unified nonlinear load current harmonics detection algorithm based on second-order general integrator (SOGI) is employed to generate both inverter line current harmonics reference and filter capacitor voltage harmonics reference at the same time. Both simulation and experimental results are presented to verify the effectiveness of the strategy.