A Modulation Method with Unfixed Switching Frequency Based on Output Power for Wind Power Converter

The wind turbine power system is being widely used and heavily connected to the utility grid, and the total harmonic distortion (THD) is one of the major evaluation indicators of electric power quality. The characteristics of the grid-connected wind converter harmonic with variable power loading are analyzed in this paper, and a software method of the variable switching frequency based on the output power of wind power converter is investigated to improve the grid-connecting harmonic considering the widely power loading. The method is verified on a three-level Neutral-Point-Clamped converter with Sinusoidal Pulse Width Modulation through simulations at last. And the results show that the THD is improved clearly and meanwhile the power loss and junction temperature are improved.