Investigation on multilevel optimal space vector PWM control technique

Space vector PWM technique has a wide application in conventional two-level bridge inverters, however it has few applications in multilevel converters except for the low number of levels for example three, four or five levels, because it becomes very difficult to choose the appropriate vector from hundreds or thousands of vectors with the increase of the number of levels by means of conventional space vector modulation techniques. This paper presents a novel Multilevel Optimal Space Vector PWM (MOSV PWM) control scheme for multilevel converters. The proposed control technique, based on space vector control theory, generates eight space vectors to be chosen and the reference space vector from the three phase voltage reference signals, and then chooses the space vector nearest to the reference space vector. The MOSV PWM technique requires constant execution time independent of the number of the voltage levels and can be applied in combination with SFO PWM technique to increase the modulation index. By means of a sensor-less induction motor speed regulation system the proposed technique is verified.