A Method for Suppressing High Frequency Resonance on MMC Converter Supplementary Control

For the high frequency resonance of MMC HVDC system, the MMC HVDC converter and the AC line impedance characteristics dependent frequency are analysed, and their mathematic model are established. The paper analyses the negative resistance inductivity characteristic of the modular multi-level converter in middle high frequency range, and proposes that the converter control circuit delay, feedforward voltage and cross-coupling term are the main factors causing the converter impedance change. Based on the above, the method of suppressing resonance of high-frequency with a low-pass filter in the control circuit improves the impedance characteristics of MMC converter, and makes the converter impedance frequency characteristics not meet the resonance condition. Using the PSCAD model of the Chongqing to Hubei BTB interconnection project, the correctness is verified by the detailed PSCAD simulation.