Space Vector based PWM scheme without sector identification for a 4-level dual inverter fed induction motor drive with asymmetrical DC link voltages

A Space Vector based PWM scheme for 4-level inverter is proposed. 4-level inversion is achieved by connecting two 2-level inverters in open-end winding configuration. The individual inverters are fed with asymmetric DC link voltages. The proposed scheme does not use sector identification method to find the sub hexagon, which encloses the tip of the reference space vector. During 3-level operation, the sub hexagon centers are directly identified from the instantaneous magnitude of 3-Phase reference sinusoid. The sub hexagon center for 4-level operation are determined from the generated sub hexagon centers for 3-level operation. The switching vectors for the two inverters are generated without using look-up tables. The scheme is implemented and tested with a 2-HP open-end winding induction motor drive. Experimental results including operation in over modulation region are presented.