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A sensorless hybrid direct torque control (DTC) drive for high-volume low-cost industrial, domestic, and automotive applications has been developed using the inexpensive TMS329F243 digital signal processor controller. Under transient operating conditions, the drive is controlled using the classic bang-bang DTC. In the steady state, using linear torque and flux controllers, the control system generates a reference voltage vector for the inverter feeding the induction motor. The vector is then realized using the well-known space-vector pulsewidth modulation (SVPWM) technique. As a result, the irregular switching pattern typical for the classic DTC strategy is replaced with a quasi-optimal one, typical for the SVPWM. Description of the drive, including a novel motor state observer, is followed by selected experimental results confirming its excellent operating characteristics.
Date of Publication: Oct. 2004