High Frequency Resonance Damping Based on Complex Coefficient Controller for the Wind Farm Connected VSC-HVDC

Due to the influence of the control delay in the Voltage Source Converter based High Voltage Direct Current (VSC-HVDC) system, the impedance phase of VSC-HVDC impedance can periodically exceed 90° when the frequency increases, while the filter capacitance in high frequency can lead the impedance phase of wind farm to be capacitive. Therefore, when the VSC-HVDC connects to a wind farm, the high frequency resonance (HFR) can occur, unless the control delay effect of VSC-HVDC can be eliminated. When considering the existence of the sub-sea cable, the impedance of wind farm side can behave pure capacitive, the resonance issue will be more serious. under this circumstance, even if the control delay effect of VSC-HVSC is eliminated or suppressed, the HFR issue still threats system stability, since the impedance phase of VSC-HVDC behaves as inductive characteristic in high frequency. Therefore, based on the existing method for control delay elimination, this paper proposed an complex coefficient controller, which can combine the existing control delay eliminator to reshape the VSC-HVDC impedance phase, to provide the sufficient phase margin for the interconnected system.