Study on Harmonic Resonance and Grid-Connected Control Technology of Doubly-Fed Wind Turbines

The development of clean energy has been paid more and more attention. The installed capacity of wind turbine is increasing, but wind turbine is prone to be affected by grid deformation as the stator of wind turbine is connected directly with power grid, and the power grid of wind farm is at the end of the whole grid, and its connection is weak. In order to reduce the influence of grid distortion on wind turbine, harmonic current suppression test was carried out on the doubly-fed wind power integration platform built based on the mathematical model of the wind power system using stator current harmonic control, and it was compared with the traditional current control method. No matter the rotational speed of the motor was subsynchronous or supersynchronous, the proposed method always had better performance in controlling harmonic current. Six times of pulse frequency of the electromagnetic torque could be effectively suppressed when the control strategy was switched from the traditional control method to the method which was put forward by this study under supersynchronous rotational speed. In conclusion, the method proposed in this paper can effectively suppress the influence of the harmonic voltage generated by the grid distortion on current in grid and improve the operation stability of doubly-fed wind motor.