Study on Control Methods of Direct-drive Wind Generation System Based on Three-phase Z-source Inverter

In this paper, a novel direct-drive wind generation system based on three-phase Z-source inverter is presented. Mathematical model of three-phase Z-source inverter is proposed by combining the traditional PWM rectifier model and equivalent model of the z-network. How variational shoot-through duty ratio affect the system is analyzed. The control method of acquiring stable Z-network capacitor voltage and decoupled d-q axis current is proposed. The relationship between variety of the shoot-through duty ratio and one of generator speed is expatiated, and a maximum power point tracking (MPPT) algorithm based on maximum power curve is designed. The whole process of tracking maximum power is analyzed by sample chart. The results of experiment on the designed prototype verify the correctness of theoretical analysis and the validity of control method.