Assessment of an improved droop control scheme for DG inverter based microgrids

In this paper an improved droop control strategy is proposed. The droop method allows inverter interfaced power units to independently feed loads according to variables measured only at the inverter connection point. The conventional droop method is however affected by an inherent issue regarding the power measurement that is necessary to deviate frequency and voltage magnitude in order to reach optimal power sharing. The conventional power measurement strategy is often based on a first order low pass filter. This implies a trade-off between a suitable power ripple rejection and the bandwidth limitation on the overall control scheme due to the inherent low frequency pole. In this paper a different filtering scheme is proposed and investigated through an analytical approach. A comparison between the conventional and the proposed control schemes is discussed through a detailed analysis. A case study of a microgrid fed by two inverters is also presented to show the improvements in dynamic performances using the proposed control architecture.