High-Frequency Oscillation Mechanism Analysis and Suppression Method of VSC-HVDC

This letter studies the high-frequency oscillation (HFO) of voltage-source converters (VSCs) in high-voltage dc transmission (HVDC). The oscillation mechanism shows that a long-time delay of the control system is the main factor affecting HFO. The existing HFO suppression schemes by software optimization, such as adding a low-pass filter (LPF) to the terminal voltage feedforward control (TVFC), etc., do not eliminate the risk of HFO. Thus, based on the mechanism analysis via the Nyquist curves in the complex plane, the design principles of the improved suppression method are proposed. Finally, the proposed schemes were confirmed by the experimental results.