Testing the Frame-Angle-Based Direct Torque Control for $3\phi$ Induction Motor Drives

This article presents the performance evaluation of the frame-angle-based (FAB) direct torque controller (DTC) for 3φ induction motor drives (IMDs), which are fed by 3 six-pulse wavelet-modulated (WM) dc-ac power electronic converters (PECs). The tested DTC is designed to adjust the d^e- and q^e-axis components of the voltages (v^e_ds and v^e_qs) applied to a 3 IMD. The adjustments in v^e_ds and v^e_qs are created in response to changes in the load torque, command torque, drive speed, and/or system parameters. Desired adjustments in v^e_ds and v^e_qs are set by regulating the angle ϑ of the frame created by v^e_ds and v^e_qs. This frame produces reference modulating signals that are required to generate WM switching pulses for operating the 3 dc-ac PEC in the IMD. The complete IMD system, incorporating the FAB-DTC, is implemented for a 10-hp IMD system for performance evaluation. Tests of the FAB-DTC for the 10-hp IMD are conducted for various changes in the load torque, command torque, drive speed, and system parameters. Simulation and experimental test results demonstrate fast, accurate, reliable, and dynamic responses with minor sensitivity to variations in system parameters.

I. Introduction

High-Performance three-phase () induction motor drives (IMDs) are widely employed in traction systems, steel mills, cranes, pulp and paper mills, etc. In such applications, IMDs are operated by several controllers, among which is the direct torque controller (DTC) [1]–[5]. The DTC is generally designed to decouple and regulate the electromagnetic torque and flux through direct modifications of the voltages applied to the stator of a induction motor. The regulation of the electromagnetic torque () and flux, via the DTC, is achieved without current controllers that are key requirements in vector- and field-oriented controls. This nature of DTC ensures its ability to initiate accurate and fast responses that are complimented by simple implementation and minor sensitivity parameter uncertainties [1]–[11]. The DTCs for IMDs have been implemented by the voltage vector selection using switching tables, direct self-control, and space vector modulation (SVM). These methods have been featured with flux observers or estimators to support the DTC accuracy and dynamics [9]–[14].