A decoupled SVPWM technique for a dual inverter four-level open-end winding induction motor drive with voltage balancing of Dc-link capacitors

Four-level inversion is realised by connecting two two-level inverters, fed from both ends of open-end winding induction motor with Asymmetrical DC link voltages in the ratio of 2:1. This inverter scheme produces 64 space-vector combinations distributed over 37 space-vector locations. All the switching combinations are not helpful to achieve four level inversion, some of the combinations overcharge DC-link capacitor of the inverter operating with a lower DC-link voltage of V_dc/3 by other inverter with higher DC-link voltage of 2V_dc/3. Decoupled space vector PWM switching strategy is described to eliminate the overcharging effect. Isolated DC power supplies are employed to avoid the zero-sequence currents. Simulation and experimental results are presented in this paper.