Transient Stability Analysis of Paralleled VSGs Considering Damping Effect

In this paper, the paralleled VSGs system's transient stability is researched with consideration of large damping effects introduced by VSG. Firstly, the paralleled model considering damping items is established, and relative motions in uniform and nonuniform damping cases, are described by second-order and third-order model, respectively. On this basis, the behavior of linear system at SEP and UEP is firstly investigated with different damping selected, and it's found the stable trajectory may exceed UEP during transient process. Furthermore, the transient stability is discussed for uniform damping cases and nonuniform ones, separately. It's found the damping items affect the equivalent parameters of swing equations, which further infect the transient stability. Besides, time-domain method is adopted for nonuniform damping system, and three instability modes are discovered with damping coefficients vary. This paper shows that the damping effect introduced by VSGs have a great impact on paralleled system's transient behaviors.