Hybrid modulation strategy of deep low carrier ratio in full wind speed for direct-drive permanent magnet wind power generation system

In high power wind turbines, the switching frequency is low because of the limitation of switching loss and system heat dissipation. In order to improve the performance of wind turbine control system, the hybrid modulation strategy of wind speed and deep carrier ratio is proposed for different speed of wind turbine. The modulation algorithm of the system is divided into 7 operating modes, and the optimal modulation strategy is selected based on the harmonic distortion rate and the maximum harmonic current amplitude. In view of the problems in the process of switching between different working sections, a three-phase synchronous switching method is proposed to realize the smooth switching between different operating modes. The correctness and feasibility of the proposed strategy has been verified in the MATLAB/Simulink simulation platform.