Transient Angle Stability Comparison of Paralleled VSGs system and Hybrid System Comprised by VSG and Diesel Generator

This paper investigates transient angle stability of parallel system of two virtual synchronous generators (VSGs) and hybrid system comprised by VSG and diesel generator (DG). Compared to single grid-connected VSG, the paralleled VSGs system and hybrid system are facing larger challenges on stability aspect during serious faults. Although there exist several publications on transient stability, the transient instability mechanism is rather ambiguous, especially for paralleled systems. Besides, swing equations of paralleled VSGs system and paralleled DG-VSG system are established to discuss the dynamic characteristics of the system during short-circuit fault. The increase of power angle between DG and VSG is caused by the different angular accelerations, which deteriorates the transient angle stability of paralleled DG-VSG system. Thus, paralleled DG-VSG system is more prone to instability than paralleled VSGs system, which can be illustrated by power angle (P-δ) characteristic curves. Finally, simulation results validate the correctness of theoretical analyses.