Suppression of synchronous resonance for VSGs

The virtual synchronous generator (VSG) is an attractive interfacing technique for high-penetration renewable generation. By incorporating the inertia control, the grid-connected voltage-source converter can behave in a similar way with the SGs, which is helpful to enhance the stability of the power system. However, it is reported that the synchronous frequency resonance (SFR) can be aroused in the VSG due to the resonance peaks in the power control loops at the fundamental frequency. By modelling the power control loop in the dq domain, the mechanism underlying the SFR is studied. It reveals the frequency shift of the grid impedance in dq frame is the origin of SFR. Moreover, the phase-amplitude cross-regulation scheme is proposed to suppress the SFR. In this way, the resonance peaks in the power control loops are completely removed, and the coupling effects between the active power and reactive power loops are also eliminated. Therefore, superior power control performances can be achieved. Simulation results verify the effectiveness of the theoretical analysis and both dynamic performance and stability of the power loops are greatly improved by the proposed cross-regulation scheme.