A decentralized multi-framed droop-controller for improving harmonic power sharing in an islanded microgrid

The nonlinear loads in microgrid not only distort the voltage but also degrade the harmonic power distribution in a conventional droop-controlled microgrid. This paper starts with analyzing the trade-off between voltage total harmonic distortion (VTHD) and harmonic sharing effectiveness. A multi-framed droop controller is proposed to improve the harmonic power sharing without deteriorating VTHD by adjusting the equivalent impedance. The inherent output impedance of inverter is reduced by multi selected-frequency resonant (R) controllers in dq frame whereas the influence of the mismatching impedance is minored by moving-average-filtered complex impedance in αβ frame. The simulation results demonstrate the effectiveness of the proposed method.