Enhanced direct torque control and predictive torque control strategies of an open-End winding induction motor drive to eliminate common-mode voltage and weighting factors

Abstract

Direct torque control (DTC) and predictive torque control (PTC) strategies emerged as powerful tools for speed control of variable frequency drives (VFD). The limitations in classical DTC and PTC are: higher ripple in torque, flux, variable switching frequency, and higher common-mode voltage (CMV). High dv/dt and CMV results in shaft voltages, bearing currents, malfunction of power electronic devices and electromagnetic interference (EMI). To eliminate the CMVs and also to reduce the switching frequency, voltage vector selection-based DTC and PTC strategies are introduced to an open-end winding induction motor (OEWIM) drive. Another limitation of classical PTC is cumbersome tuning of weighting factors. To address this limitation, modified cost function-based PTC strategy has been developed to eliminate weighting factors. OEWIM drive operates with dual inverter configuration and the two inverters are operated with equal DC-link voltages; therefore, it delivers three-level output voltage. This article introduces various DTC and PTC strategies to an OEWIM drive to reduce torque, flux ripples, switching frequency, elimination of CMV, and weighting factors. The effectiveness of proposed DTC and PTC strategies is tested by dspace-1104 real-time interface controller and comparing the obtained results with classical DTC and PTC.