Current-controlled offshore wind turbines connected with DRU-HVDC

With the fast development of the offshore wind farms, how to reduce the transmission cost draws increasing attention. Diode-rectifier-unit based HVDC (DRU-HVDC) is a potential way to address this issue. For such a system, the control of the line-side-converter of wind turbines plays a key role on its reliable operation. This paper proposes a novel current-controlled solution for the offshore wind turbine converters, which consists of an inner current control loop, phase-locked loop, active/reactive power loop and frequency control. Comparing with the historically-reported voltage-controlled turbines, the proposed control eliminates the dq voltage control loops, providing the advantages of less parameter tuning. Simulation results in PSCAD/EMTDC demonstrate the effectiveness of the proposed current-controlled offshore wind turbines connected with DRU-HVDC during the start-up, string outage and reactive power compensation outage.