Mechanism Analysis and Suppression Strategy of Continuous High-Frequency Oscillation in MMC-HVDC System

The continuous high-frequency oscillation phenomenon of the MMC-HVDC system occurs frequently in practical engineering. How to design an effective oscillation suppression strategy based on the essential mechanism of continuous oscillation has not been sufficiently supported by theory. For this reason, this paper firstly analyzes the high-frequency oscillation characteristics of the MMC-HVDC system. On this basis, considering the influence of the control system time delay, the MMC high-frequency impedance model is established based on harmonic linearization. Thirdly, the dynamic interaction between the control system and the harmonic disturbance is analyzed, and the continuous oscillation mechanism of the MMC-HVDC system is revealed. Finally, a high-frequency oscillation suppression strategy is proposed, consisting of adding a nonlinear low-pass filter to the MMC voltage feedforward link and reducing the risk of oscillation in the 0–2000 Hz frequency band. The simplified impedance model and high-frequency oscillation suppression strategy are verified in time simulation