A Virtual Inertia Control Strategy to Improve Transient Responses of VSC-HVDC Systems

The topology of a VSC-HVDC system was similar with that of a synchronous generator (SG), because power controlled converter was analogous to a prime mover and DC voltage controlled converter was analogous to the SG. Importantly, the dynamics of DC-side capacitor were highly similar with that of the rotor. Hence, in this paper, the motion equation used in SG can be applied to VSC-HVDC system to identify the DC-side stability of the system. Moreover, a supplementary power converter was added and paralleled on the inverter station to implement virtual inertia control actions. And it was validated the virtual inertia control behaves as increasing the inertia of DC systems when increasing a virtual capacitance on the original capacitor. Besides, the virtual inertia control was good to the DC-side stability of VSC-HVDC system and enhance damping performance. And it can slow down the response of the system when subjected to a disturbance. And the rate of change of DC voltage was slowed down; the deviation of DC voltage was decreased as well, which was beneficial to improve the DC voltage nadir and keep the stable operation of system. The theoretical analysis was validated by simulations.