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The dual two-level inverter fed open-end winding induction motor drive gives voltage space phasor locations similar to a three-level inverter fed induction motor drive. The dual inverter scheme renders advantages such as redundancy of the space vector combinations for the same number of space vector locations and the absence of neutral point fluctuations. In a dual-inverter scheme, a total of 64 space-vector combinations are distributed over 19 space vector locations compared to 27 space-vector combinations distributed over the same number of locations in a three-level inverter. The common mode voltages (the harmonics of the triplen order) need to be suppressed by transformer isolation or the use of harmonic filters. In this paper, a space vector modulation scheme for the suppression of zero sequence currents (the harmonics of the triplen order) for a dual two-level inverter fed open-end winding induction motor drive is described. The proposed scheme does not require bulky transformers or harmonic filters for the elimination of the zero sequence currents. The proposed space vector PWM is based on the observation that certain voltage space-vector combinations in the dual inverter scheme do not contribute to the triplen harmonics and hence the PWM scheme that exclusively employs these combinations is used to eliminate the triplen harmonic currents.

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A power circuit configuration to realise three-level inversion is proposed. Three-level inversion is realised by connecting two two-level inverters in cascade, in the proposed configuration. An isolated DC power supply is used to supply each inverter in this power circuit. Each DC-link voltage is equal to half of the DC-link voltage in a conventional NPC (neutral point clamped) three-level inverter topology. Neutral point fluctuations are absent, and fast recovery neutral clamping diodes are not needed. The proposed inverter scheme produces 64 space-vector combinations distributed over 19 space-vector locations as compared to 27 combinations in a conventional three-level topology. The present power circuit can be operated as a two-level inverter in the range of lower modulation, by clamping one inverter to a zero state and by switchng the other inverter. When compared to the H-bridge topology, this circuit needs one power supply less. A space vector based PWM scheme is used for the experimental verification of the proposed topology.

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A dual two-level inverter fed open-end winding induction motor drive is proposed in this paper. A total of 64 voltage space phasor combinations are possible in this scheme since each