Space vector PWM strategy for 3-level inverters with direct self-control

A novel pulse width modulation (PWM) strategy for induction motor drives with direct self-control and a free-running 2-level torque controller is described. The technique is based on space vector modulation achieved with look-up tables and logic circuits. The method is very flexible allowing the generation of many PWM patterns, including switching preferences and avoiding 3-level inverter switching collisions. In the paper, detailed consideration is given to the PWM patterns consisting of full, intermediate and half voltage vectors. The techniques of generating of dodecagonal flux trajectory and of reducing stator current reactive distortion with 2-level torque control are demonstrated. Methods for neutral point voltage control are proposed and the problem of a drive transition from a 6-pulse to a 12-pulse mode is discussed. The properties of the method are illustrated by simulation of a high-power traction drive