A Novel Method to Improve the Transient Performance of Virtual Synchronous Generator by Adding a pair of Pole-Zero in the Rotor Inertia

The virtual synchronous generator (VSG) is favored in distributed generation units because it can reduce the rate of change of frequency (ROCOF) in the inverter stand-alone mode. Although the rotor inertia and damping factor can improve the frequency stability of the grid, they deteriorate the transient performance in the grid-connected mode with high current overshoot and power oscillation. The existing solutions improve the transient performance at the cost of larger ROCOF or complex adaptive algorithms, which can sacrifice some frequency stability or lead into potential uncertainties. Aiming at solving this problem effectively, this paper proposes a novel method by adding a pair of pole-zero to the rotor inertia. In this way, the VSG control can not only greatly improve the transient performance in the grid-connected mode, but also the same good ROCOF is maintained for the stand-alone mode. Firstly, the small signal model of VSG control with the improved rotor inertia is derived based on the traditional VSG control. Then the improvement caused by the pole-zero in rotor inertia is analyzed in frequency domain in detail. Finally, the effectiveness of the proposed method is validated by experimental results.