A low-order AC-frequency and DC-voltage response model of HVDC grid connected with wind farms

A low-order and fairly accurate model for fast computation of wind farm (WF) ac system-frequency and high voltage direct current (HVDC)-voltage responses following disturbances is developed. Considering a complete WF as virtual synchronous generator (VSG), the WF-side voltage source converter (VSC) is controlled using proposed VSG vector-control strategies. Then, a novel transfer function-based system frequency response (SFR) model of WF-side ac systems is derived. In accordance with the frequency regulation principle in interconnected power systems, dc-voltage response model (DC-VRM) of multi-terminal HVDC system is developed. Based on the SFR and DC-VRM, dynamic behavior of WF-MTDC system is readily illustrated with a compact form of the transfer function, resulting in a convenient method performing control system design and stability identification including selecting compensator functions and tuning the parameters. Comparison of the results with that obtained from electromagnetic transient model confirms the accuracy and effectiveness of the proposed ac-frequency and dc-voltage response model.