MPC-based DC-link voltage control for enhanced high-voltage ride-through of offshore DFIG wind turbine

Abstract To deal with the DC-link overvoltage during high-voltage ride-through (HVRT) of the wind turbine, a coordinated DC-link voltage control (CDVC) scheme is proposed for enhancing the HVRT performance of offshore doubly-fed induction generator (DFIG) wind turbines equipped with the supercapacitor energy storage system (SESS). This scheme is formulated as a two-stage control problem depending on the depth of grid voltage swell, which can prevent damaging the converter resulting from the insufficient reactive support in the first stage, and achieve efficient coordinated control under various magnitude and timescale of grid voltage swell. In the first stage, considering the dynamic behavior of the DFIG during HVRT, a voltage-dependent reactive current control (VRCC) scheme is designed to regulate the current reference of the wind turbine. The first stage aims to supply fast reactive current support without the DC chopper. In the second stage, once the DC-link voltage exceeds the predefined threshold, a coordinated control scheme considering the SESS and the wind turbine operation is implemented using model predictive control (MPC), aiming to regulate the excessive active power by tracking the current reference from the first stage. The proposed control scheme is validated in PSCAD/EMTDC under various operational scenarios. Case study results show that the proposed scheme can effectively mitigate the DC-link overvoltage and enhance HVRT capability under asymmetrical and symmetrical voltage swells.