Three-level inverter scheme with common mode voltage elimination and DC link capacitor voltage balancing for an open-end winding induction motor drive

A dc link capacitor voltage balancing scheme along with common mode voltage elimination is proposed for an induction motor drive, with open-end winding structure. The motor is fed from both the ends with three-level inverters generating a five level output voltage space phasor structure. If switching combinations, with zero common mode voltage in the pole voltage, are used, then the resultant voltage space vector combinations are equivalent to that of a three-level inverter. The proposed inverter vector locations exhibit greater multiplicity in the inverter switching combinations which is suitably exploited to arrive at a capacitor voltage balancing scheme. This allows the use of a single dc link power supply for the combined inverter structure. The simultaneous task of common mode voltage elimination with dc link capacitor voltage balancing, using only the switching state redundancies, is experimentally verified on a 1.5-kW induction motor drive.