High-Frequency Resonance Coordinated Suppression Method of MMC-HVDC Systems Under Frequency Divided Voltage Feedforward Control

In the modular multilevel converter (MMC) based high voltage direct current (HVDC) practical projects, the existing voltage feedforward control (VFC) method presents challenges in addressing the frequency shift of high-frequency resonance (HFR) caused by the changes in the interconnected AC system's operating conditions. In this paper, the mathematical characterization function of the impedance real part is used to reveal the mechanism why the existing VFC cannot simultaneously reshape the multiple HFR risk regions into the positive damping characteristics. Therefore, a frequency divided voltage feedforward control (FDVFC) based on the second-order band-pass filters (BPFs) is proposed to simultaneously reshape the multiple HFR risk regions into the positive damping characteristics. The proposal includes the selection of the number of BPFs and how to design their parameters. The parameter design principles and parameter selection ranges of the BPFs are presented one by one using the simplified model of the MMC in high-frequency band. Finally, the effectiveness and correctness of the FDVFC and its analytical calculation expressions for parameter selection are verified by time-domain simulations.