As the penetration of renewable energy sources is increasing in the AC micro-grid, the stability of the closed-loop system has raised a major concern since conventional distributed interface converters (DICs) used in the AC micro-grid do not have a rotating mass, and hence low inertia. High penetration of DIC-based micro-grid may result in poor frequency and voltage response during large disturbance. In order to overcome this difficulty, the virtual synchronous generator (VSGs) was proposed recently in which the DIC mimics conventional synchronous generators (SGs) by designing proper parameters of the SG into each local droop control mechanism of the DIC. Meanwhile, due to the recent advances of distributed control, the concept of consensus-based control can be applied to study this droop control problem of VSGs. One important feature of this consensus-based control is that it can be implemented on each local DIC with communications among their neighboring DICs. In contrast to most existing secondary control schemes, no central controller is required. Under this framework, if DICs are redesigned as VSGs, the frequency and voltage of each DIC can be restored to their pre-specified values obtained from the steady-state analysis. In addition, the proper real and reactive power sharing still can be achieved according to the nominal rating of each DIC. The stability of the closed-loop system is ensured by the transient energy function under certain mild conditions. Numerical experiments of a 14-bus/6-DIC micro-grid system on real-time simulators are performed to validate the effectiveness of the proposed control mechanism. Index Terms-Consensus algorithm, distributed interface converters (DICs), droop control, micro-grid (MG), transient energy function (TEF), virtual synchronous generator (VSG). 2156-3357

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Micro-grid is a system with various distributed energy sources integrated. Due to its inherent distributed and heterogeneous nature, the micro-grid becomes ideal platform for consensus-based multi-agent control. Conventionally, power sharing in a micro-grid is achieved by autonomous P f − and Q V − droop control on individual inverters, which suffers from lack of frequency restoration mechanism and dependence on output line impedance. While the previously developed Q V − droop control still ends up with inaccurate reactive power sharing under strongly non-uniform line impedance. In this paper, a consensus-based P f − and Q V − droop control with sparse communication network is proposed. With the networks considered to be lossy, its operation principle and control method are explained, and stability of the closed-loop system is investigated by the energy function approach. Simulation results of a 4-node 3-inverter system are then presented to validate the effectiveness of the proposed control method.

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