A Virtual Admittance-Based State Observer Design for Enhanced Dynamic Synchronization Performance of Virtual Synchronous Generator

The virtual resistor (VR) has positive effects on the small-signal stability of the virtual synchronous generator (VSG), but decreases the dynamic-state synchronization performance. To solve that conflict, a virtual admittance (VA)-based state observer (VABOB) is designed. First, the small-signal model of the VSG is analyzed, and it is found that the extra VR is only needed at 0 Hz to suppress the synchronous frequency resonance (SFR). The extra resistor at the synchronous frequency (SF) will decrease the dynamic response performance. Second, a state equation is designed for the accurate estimation of the SF component, and the VA without VR is designed as the output equation. Then, the state observer is deduced based on these equations. Third, the analysis of the grid voltage and frequency deviation shows the robustness of the VABOB. Furthermore, the selection principle for the observer gain is also analysed. Simulations and experiments verify the effectiveness of the VABOB in SFR suppression and dynamic performance enhancement by reducing theR/X. The VABOB can reduce the maximum by 0.39 p.u. power overshoot when the grid voltage is sagged by 0.1p.u., as compared to the VR-based method withR/X= 0.19. By 0.55 p.u. reactive power overshoot reduction when power given is increased from 0 to 1 p.u., as compared to the VR-based method withR/X= 0.83.