PUBLICATIONS

A direct torque control algorithm for 3-level inverter-fed induction motors is presented. Conventional voltage selection methods

provoke some problems such as stator flux drooping phenomenon and undesirable torque control appeared especially at the low

speed operation. To overcome these problems, a proposed method uses intermediate voltage vectors, which are inherently

generated in 3-level inverters. In the proposed algorithm, both subdivision of the basic switching sectors and applications of

intermediate voltages improve the low speed operation characteristics. This algorithm basically considers applications in which

direct torque controlled induction motors are fed by 3-level inverters with low switching frequency around 500Hz. An adaptive

observer is also employed to bring better response at the low speed operation, by estimating some state-variables, motor speed

and motor parameters which take a deep effect on the performance of the low speed operation. Simulation and experiment results

verify effectiveness of the proposed algorithm.