Start-up and integration of DFIG-based wind farm using modular multilevel VSC-HVDC transmission system

This paper describes the start-up and integration of a doubly fed induction generator (DFIG)-based wind farm into the ac network through a voltage source converter-based (VSC) HVDC transmission system. A control strategy based on the closed-loop control of rotor current is proposed during DFIG cut-in process. In normal operation, an additional feedback signal is introduce to the control system of the wind farm side modular multilevel convert (WFMMC) in order to eliminate the output current ripples of the wind farm. Meanwhile, grid side modular multilevel converter (GSMMC) is controlled to maintain a constant dc voltage. Simulation waveforms and field tests results are presented to validate the effective performances of the proposed control strategies in this paper.