Control loops design in a grid supporting mode inverter connected to a microgrid

This paper deals with some design aspects of the control loops in a droop-controlled VSI connected to other inverters of greater ratings or to a strong grid, which sets the frequency. The design of a damping resistor in series with the AC filter capacitor is discussed and the impact of strong feedback between the output current and the capacitor voltage is investigated. Moreover an analysis of the derivative droop coefficients is carried out through a simplified equivalent circuit.