Dual Three-level Soft Switching Converter for DC Grid-connected of Large-scaled Wind Turbines

Along with the increase of their generation capacities and offshore distances, wind farms with DC collection and avoiding overvoltage have been aroused more and more attention. As the mainstream model of the offshore wind power exploitation, the direct-drive wind turbine realizes DC interconnection through the design of the DC/DC converter. Firstly, a scheme for dual three-level soft switching DC/DC converter is proposed considering the demand of the DC wind turbine, which effectively reduces the converter volume and its switching losses. Secondly, through a detailed analysis of the working principle of the sub-converter, a method for designing the important parameters of the sub-converter is given. Then, the control strategies in both the normal and the fault periods are given based on the control objectives of the DC/DC converter, ensuring the safe, stable and efficient operation of the turbine. Finally, the superiority of DC/DC converter topology and the effectiveness of control strategy are verified by simulation results.