Performance of a hybrid current-controlled VSI fed permanent magnet synchronous motor drive

Permanent-magnet synchronous motors are widely used in modern variable speed AC drives. This is achieved by using a current controlled PWM voltage source inverter (VSI) system. In this paper, both the hysteresis current controller and the ramp comparator are presented and their performances are evaluated. Each current control scheme has its own advantages and drawbacks throughout the entire range of speeds. A hybrid controller, in which a combination of a hysteresis controller for high-speed operation and a ramp comparator controller for low-speed operation is proposed to overcome the drawbacks of each controller. Comparative performances of the different types of current controllers under vector control technique are presented. The proposed scheme gives significant improvement in the system performances over existing methods