Hierarchical Control for Compensation of Voltage Harmonics in Islanded Microgrids

In this paper، a hierarchical control scheme consisting of primary and secondary levels is proposed for compensation of voltage harmonics in islanded microgrids. The primary control level comprises Distributed Generators (DGs) local controllers. Each of these controllers includes a harmonic virtual impedance loop which is considered to improve nonlinear load sharing among the DGs، but، at the expense of increasing the voltage harmonic distortion. The secondary control level manages the compensation of voltage harmonics by sending proper control signals to the primary level. Since، the microgrid may supply sensitive loads; the compensation is performed to reduce load bus main voltage harmonics. The procedure of setting control system parameters is presented and simulation results are provided in order to demonstrate the effectiveness of the proposed control scheme.