Secondary-control-based harmonics compensation scheme for voltage- and current-controlled inverters in islanded microgrids

In this study, a coordinated control scheme is proposed for sharing harmonics compensation effort among voltage and current controlled mode (VCM and CCM) inverters in islanded microgrids. In this method, the voltage harmonics compensation of sensitive bus (SB) is achieved by using secondary control as well as virtual impedance and admittance loops in primary control of VCM and CCM units. The limited capacity of the inverter is taken into account for harmonics compensation. Photovoltaic (PV) systems are considered as CCM units. The harmonics compensation is mainly performed by VCM inverters. However, in order to prevent these units from overloading, the PV interfacing inverters (CCM units) are called to collaborate in harmonics compensation whenever needed. The results of simulation study in Matlab/Simulink show the effectiveness of this method in coordination of CCM and VCM units.