Torque and Speed Response Differences Between Deadbeat-Direct Torque and Flux Control and Indirect Field Oriented Control for Induction Machine Drives

Abstract

Indirect field oriented control (IFOC) is widely used in induction machine (IM) drives. IFOC controls torque and rotor flux linkage by using an embedded current regulator. The torque and speed response are limited by current regulator bandwidth. Different from IFOC, without any current regulator, deadbeat-direct torque and flux control (DB-DTFC) calculates the voltage commands directly, which can achieve torque commands within just one switching period. However, high frequency torque and speed response have not been systematically discussed. First, IFOC, DB-DTFC algorithm and implementation issues are discussed in details. Then, the metric for evaluating the high frequency torque and speed response are proposed and evaluated. In the torque response, the DB-DTFC drive shows higher torque command tracking bandwidth with linear phase lag compared to IFOC drive. In the speed response, parameter sensitivities of high frequency speed command tracking for the two control algorithms are compared with encoder feedback. Finally, the speed response in the self-sensing mode for the two control algorithms are also compared.