A robust active damping method to improve the parallel operation of micro-inverters in islanded microgrids

To fully exploit the energy of photovotaic (PV) panels, a sub-module MPPT strategy (known as distributed maximum power point tracking) is extensively utilized in PV systems. This strategy is performed using the micro-inverters which serve as the interfaces of PV panels. Therefore, ac microgrids equipped with large scale PV panels, are expected to be dominated by micro-inverters. This paper investigates the parallel operation of a large number of micro-inverters in islanded microgrids. It is shown that stability of ac microgrids is jeopardized under a high penetration of micro-inverters. This is done using the impedance stability analysis and with the help of pole map of the whole ac microgrid. Moreover, a robust active damping approach is proposed. This approach improves the parallel operation of ac micro-invertes and prevents the instability of ac microgrids. Different simulation scenarios are provided to validate the findings and effectiveness of the proposed active damping approach.