An improved single-vector-based Duty Cycle Control Method for Direct Torque Control of Induction Motor

Duty cycle control (DCC) is a powerful solution to reduce the torque error in direct torque control method. According to this method, during a control cycle, the zero voltage vector is applied to adjust the length of the applied active voltage vector. In prior switching-table-based duty cycle methods, the selection of the active voltage vector is done according to the sign of the initial electrical torque and stator flux errors. whereas, in this strategy, the suitable voltage vector is not selected in some operation states. In this paper, a new solution is presented to find the best active voltage vector that reduces the torque and flux errors under all operating conditions. Next, the minimum-torque-error optimization is used to calculate the optimal value of duty cycle. Simulation results are presented to examine the proposed method performances and compare it with traditional DTC and prior duty cycle control methods.