New model of multi-parallel distributed generator units based on virtual synchronous generator control strategy

Abstract

Virtual synchronous generator (VSG) control technique presents a promising alternative for controlling the inverter-based distributed generator (DG), due to its capability to improve the microgrid stability when the renewable energy has a high penetration level into the grid. The analyses and parameters design of the active and reactive power loop of DG are often based on a small-signal model, where a linear relationship between active and reactive powers versus control variables is obtained based on quasi-static method, in which the currents dynamic is neglected. This model gives qualitative results only in case of large conventional synchronous generators. However, for a small DG based on VSG controller with a small virtual inertia, fast power electronics devices and with coupling between active and reactive powers loops, this model does not give satisfactory results. To overcome the aforementioned problem, this paper proposes a new model of DG systems based on VSG operating in island microgrids. The proposed model incorporates the line impedance dynamic of the microgrid into the DG model. The accuracy of the proposed model has been investigated and compared with the conventional one using MATLAB/Simulink environment. Simulation obtained results prove that the new model is more precise compared to the conventional one in transit state reflecting by the way better the dynamics of the system and allowing as a consequence of a good analysis of the stability and behaviour of the global system.