Fully Distributed Hierarchical Control of Parallel Grid-Supporting Inverters in Islanded AC Microgrids

In this paper, a fully distributed hierarchical control strategy is proposed for operating networked grid-supporting inverters (GSIs) in islanded AC microgrids (MGs). The primary control level implements frequency and voltage control of an AC MG through a cascaded structure, consisting of a droop control loop, a virtual impedance control loop, a mixed H_2/H_infinity based voltage control loop and a sliding mode control (SMC) based current loop. Compared to conventional proportional plus integral (PI) based cascaded control, the proposed cascaded control doesn't require a precise model for the GFI system. The proposed secondary control level implements distributed consensus based economic automatic generation control (EAGC) and distributed automatic voltage control (AVC), which integrates the conventional secondary control and tertiary control into a single control level by bridging the gap between traditional secondary control and tertiary control. Simulation results demonstrate the effectiveness of the proposed hierarchical control strategy