Sequence-Impedance-Based Stability Comparison Between VSGs with and without inner loops control

As one of the most promising control strategies, virtual synchronous generators (VSG) control is studied worldwide and impedance models have been built for VSG by some papers, but most of them overlook the inner loops which can make significant difference to impedance of VSG. This paper establishes the sequence impedance models of VSG with and without inner loops and demonstrates the negative influence of inner loops on dynamic performances in the range of low frequency by the comparison of impedance models of VSG with and without inner loops. Then the paper gives suggestion that virtual resistance should be adopted to the VSG with inner loops to improve stability. Finally, all the theoretical analysis is verified by simulation results.