Three phase parallel three level inverter fed induction motor using PD modulation scheme

This Paper presents the Phase Disposition Scheme, which is topology independent. This scheme is used in Multilevel Inverters, interleaved parallel combination. Analysis on the other scheme which is Phase Opposition Disposition has also been performed. The best strategies related to the paralleling of inverters are evaluated, particularly those associated to current balancing between two cells. Pulse width modulation (PWM) strategies and methods for multilevel converters are usually developed for series converters. In this paper it is shown that they may be applied to parallel converters using interleaving techniques, given that these converters also have multilevel characteristics. PWM methods based on carriers' disposition and on zero sequence injection are studied for parallel multilevel inverters. Analysis shows that the best method in terms of load current ripple is the phase disposition method. The current balancing between commutation cells of the same phase is comparatively superior with this method. Another objective on which work was done was to analyze these problems and to propose a solution to cancel current imbalance when using PD strategy. In addition to the above scheme POD (Phase Opposition Disposition) strategy has also been simulated which has shown comparatively same results as that of the PD strategy. The load was chosen to be a three phase induction motor drive and its parameters such as Stator Current, Speed and Electromagnetic Torque have been analyzed as such.