A dynamical multi-input/multi-output network formulation for stability analysis in AC microgrids

Nowadays, we have witnessed a significant increase of renewable sources across the existing power grids as a result of the undeniable need to mitigate the effects of environmental pollution and to assist the economic development of the countries. However, due to the lack of rotational inertia and their intermittent nature, renewables have increased the severity of the occurring disturbances and instability phenomena, which in turn, place a demand for more accurate modeling of the grid and the power system components. In this paper, we propose a novel network formulation for AC microgrids that allows the consideration of less conservative conditions for the network whilst facilitating the adoption of higher order inverter-based generation dynamics and the stability analysis and control. In particular, we formulate the network as a dynamical multi-input/multi-output system, which we show is both stable and passive, even when the network's dynamic and lossy nature is considered. Then we present the opportunities and the advantages offered by the proposed framework and provide useful guidelines for a more accurate modeling of power system components. Finally, we verify the proposed network formulation through a numerical application on the Four Machine Two Area Kundur test system and a dynamic simulation on typical Medium Voltage (MV) distribution lines.