Vahid Faraji

  Abstract

  In thesis proposed a direct torque control (DTC) scheme for induction motor drive system fed by indirect matrix converter. DTC is a high performance motor control scheme with fast torque and flux response. However, the main disadvantage of conventional DTC is electromagnetic torque ripple. By suitably selecting switching pattern, conventional problem of DTC such as electromagnetic torque and flux ripple of the motor is effectively reduced. Using this switching strategy, the advantages of the DTC schemes and the benefits of the indirect matrix converter can be combined.

  New methods of improving torque ripple are introduced in this thesis. In the rectifier stage, in order to reduce losses caused by circuit snubber the rectifier four-step commutation method is employed. To improve the dynamic behavior of motor, Active Learning Method (ALM) is implemented on the DTC. The ALM uses its own modeling technique called the ink drop spread (IDS) method.

  Since the indirect matrix converter has an intermediate dc link, the control process can be separated into rectifier stage modulation and inverter stage modulation. Indirect space vector modulation (ISVM) for input current is applied on the rectifier bridge, while the inverter and motor can be seen as constant current load in DC link and ISVM for output voltage is applied on the inverter bridge. The modulation processes of rectifier stage and inverter stage are considered simultaneously.

  Date of Defense: Saturday: januery 29 2011