A low computation fractal based voltage space phasor generation for a four level inverter using open-end winding induction motor drive

Abstract

A Space Vector based Pulse Width Modulation scheme for a 4-level inverter in open-end winding configuration isproposed. An approach based on fractal theory is used to find the sector and the inverter switching vectors. The space vector locations and associated computations are performed in 60° coordinate framework. This representation avoids fractional arithmetic, thereby reducing computational complexity compared to the methods based on Cartesian coordinate system. Mapping to 2-level is used to determine the duration of switching vectors. The scheme is experimentally verified by using a 4-level inverter configuration. 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 switching vectors for the two inverters are automatically generated without using look-up tables. The scheme is implemented and tested with a 2-HP openend winding induction motor.