Dynamic Frequency Trajectory Prediction Assisted Frequency Response Method for Lightweight MTDC Systems

This paper proposes a dynamic frequency trajectory (DFT) prediction assisted frequency response method (FRM) for the diode rectifiers (DR) and modular multilevel converters (MMC) based lightweight multi-terminal direct current (MTDC) systems. First, an improved state-space primary frequency regulation (SSPFR) model is established. Different from the existing primary frequency regulation (PFR) models, the proposed SSPFR model has fully considered spatial frequency distribution. Next, to cope with the prediction task of the DFT under continuous disturbances (CD-DFT), a novel CD-DFT prediction method based on the modal analysis is proposed, by which the prediction timeliness can be significantly improved. Then, the DFT assisted FRM is proposed, for improving the PFR performance of the lightweight MTDC systems while ensuring security operation. Finally, the proposed method is verified on a modified IEEE 39-bus system. The numerical results demonstrate that the proposed method can effectively exploit the frequency regulation potentialities of offshore wind farms connected to the lightweight MTDC system.