Small signal modeling and parameter design of virtual synchronous generator to weak grid

The virtual synchronous generator (VSG) allows power electronics interfaced distributed generators (DG) actively taking part in the power regulation of distribution network (DN), providing adjustable inertia and damping as well as frequency and voltage support, which is meaningful to facilitate the safe and stable operation of DN. However, the dynamic characteristics of VSG have not yet been discussed when the frequency and amplitude of grid voltage are disturbed. To evaluate the power regulation capabilities of VSG, it is thus necessary to unmask the dynamic characteristics of VSG, especially when it is connected to weak grid. To address this issue, a small signal model of VSG controlled three-phase converter is first deduced. On this basis, the relationships of power responses and grid voltage disturbances are revealed. In order to improve the dynamic performances and reduce coupling effect between active and reactive power regulation, the influence of main parameters involving inertia, damping, voltage regulation coefficient and virtual impedance on dynamic response is analyzed by root locus and the parameter design method is presented. Finally, the Matlab/Simulink simulation and experimental results show the correctness and feasibility of the theoretical analysis presented above.