Transient Voltage Coordination Control Strategy for Doubly-fed Wind Turbines Based on Power Balance under Asymmetric Faults

The new power system puts higher demands on the supporting role of renewable energy turbines in the transient process of the power grid. The transient characteristics of doubly-fed wind turbines during asymmetrical faults are analyzed, and the influence weights and evolution laws of transient DC components and asymmetrical components are revealed. Combined with the newly published standard of fault ride-through for doubly-fed wind turbines, coordinated control guidelines and methods for doubly-fed wind turbines during fault ride-through are proposed. For the rotor-side converter, on the basis of considering the power balance with the grid-side converter, the feedforward compensation of rotor counter-potential based on stator current differentiation and the control method of negative-sequence current coordinate transformation are proposed, which reduces the complexity of the rotor-side control and ensures the reactive power regulation during the fault period. For the grid-side converter, the negative-sequence component suppression strategy is proposed, which reduces the effect of the negative-sequence component on the voltage quality. Finally, the simulation model of the doubly-fed wind turbine connected to the AC grid delivery scenario is constructed in the PSCAD/EMTDC simulation platform to verify the feasibility and superiority of the proposed control strategy.