A New Virtual Harmonic Impedance Scheme for Harmonic Power Sharing in an Islanded Microgrid

This paper proposes a control strategy for harmonic power sharing in an islanded microgrid, without affecting the voltage quality at the load bus. The harmonic power distribution in an islanded microgrid depends on the line impedance. The proposed control strategy employs negative virtual harmonic impedance to compensate for the effect of line impedance on harmonic power delivery. The influence of mismatched line impedances on nonlinear load distribution is minimized by virtually varying the effective line impedance at harmonic frequencies. The fundamental active and reactive power sharing is implemented using the droop technique and the proposed method operates independently, without affecting the linear load sharing. Furthermore, a new droop method, called Z(h) - H droop, is also proposed to estimate the virtual harmonic impedance value adaptively. The proposed concept of negative virtual harmonic impedance and Z(h) - H droop is validated using simulation and digital signal processor- based experimental studies.