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A sensorless direct torque controlled (DTC) induction motor drive fed by a 3-level inverter is presented based on discrete space vector modulation. A novel vector synthesis sequence is proposed to solve the problems caused by the topology of the 3-level inverter, such as neutral point unbalance and excessive voltage jump, while maintaining the merits of simplicity and robustness. Fuzzy logic control and speed adaptive flux observer are introduced to enhance the performance of system. The problem of large starting current is investigated and solved by introducing the technique of pre-excitation. A 32-bit fixed-point DSP based 3-level motor drive has been developed and a series of experimental results are presented to confirm the effectiveness of the proposed techniques.
Date of Conference: 27-30 Sept. 2009