Voltage Unbalance and Harmonic Compensation through Distributed Generation with Virtual Impedance Control in Islanded Microgrid

The power sharing and voltage quality are more challenging in islanded microgrids with the unbalance or nonlinear loads. Distributed generations (DGs) can be used to improve the power quality in the microgrids. However, when multiple DGs are participated for the voltage unbalance or harmonic compensation, conventional droop control can cause poor power sharing among the DGs due to mismatched line impedance. This paper proposes a control method of the virtual impedance for proportional sharing of the unbalance or harmonic power. The virtual unbalance or harmonic impedance is adaptively controlled for decreasing of the unbalance or harmonic power sharing error among the DGs. Consensus algorithm is adopted for the adaptive control of the virtual impedance. This method does not require the prior knowledge of the line impedance. Simulation results are presented to validate the proposed method for proportional sharing of unbalance or harmonic power with reducing the unbalance or distortion of voltage at point of common coupling (PCC).