Coupling stability analysis of synchronous generator and virtual synchronous generator in parallel under large disturbance

With the development of virtual synchronous generators (VSG), microgrids can choose a synchronous generator (SG) or a virtual synchronous generator (VSG) as the main power supply of an isolated island system. The governor of a synchronous generator and the active power control loop of a virtual synchronous generator may cause the transient power angle instability of the system, while the excitation device and reactive power control loop may cause the transient voltage instability. At present, there have been many studies on these two aspects. However, when a synchronous generator and a virtual synchronous generator are used as the main power sources to supply power to the isolated island system, the mutual coupling between the synchronous generator and the virtual synchronous generator may cause transient power angle and voltage instability. At present, there is little research in this field. Therefore, this paper focuses on the influence of the parallel mutual coupling of synchronous generator and virtual synchronous generator on the system stability, derives the mutual coupling model of a parallel system, it is also revealed that the coupling relationship between the SG and VSG parallel systems will produce a positive feedback mechanism that will be constantly amplified, which will greatly affect the system's stability. At the same time, the influence of coupling on the stability of a parallel system is carefully analyzed using large signal analysis, and the corresponding coupling suppression strategy and adaptive inertia control (AIC) is proposed. Finally, the correctness and feasibility of the proposed method are verified by timedomain simulation, and the experimental results are analyzed.