Modeling and Analysis of Transient Overvoltage of Direct Drive Wind Turbine Under Symmetrical Faults

Large-scale wind power bases typically adopt UHVAC/UHVDC transmission systems for power export, with weak grid strength in the collection area. After short-circuit faults, transient overvoltage issues are prone to occur, making it urgent to study the analytical model of transient overvoltage during short-circuit faults in wind turbine generators. Firstly, a transient voltage model after a symmetrical short-circuit fault at the remote end of the transmission line in a weak grid is established based on the typical control and voltage ride-through strategies of permanent magnet synchronous generator wind turbines. By studying the transient voltage components at the grid connection point corresponding to the voltage at the fault point, it is revealed that transient overvoltage may occur at the grid connection point after the instantaneous recovery of the fault point voltage. Secondly, a second-order simplified model suitable for transient overvoltage analysis is proposed, and clarify that the damping ratio of the simplified model is a key factor determining the peak overvoltage value. The expression of peak overvoltage is solved through time-domain analysis, and the influencing factors of transient overvoltage are quantitatively analyzed. Finally, relying on the control hardware-in-the-loop real-time simulation experimental platform, the applicability of the proposed simplified transient overvoltage model and the dominant influencing factors of transient overvoltage are verified.