Closed-loop hybrid direct torque control for medium voltage induction motor drive for performance improvement

This study presents the hybrid direct torque control (HDTC) method for medium voltage-range induction motor (IM) drive. The control method comprising the torque control by rotor-reference frame quadrature-axis current instead-of conventional DTC and speed control similar as in space-vector-modulation (SVM)-DTC is proposed. Hence the scheme is referred as HDTC. A carrier-based space-vector-modulation controlled five-level diode-clamped multilevel inverter with proposed control scheme is providing promising-step towards performance enhancement of IM drive in respect of torque ripple contents and steady-state performance over wide speed-range. The effectiveness of the proposed control scheme is confirmed by comparison with DTC in matlab-simulink. A prototype is fabricated for three-phase, 3-HP IM. A 32-bit fixed-point DSP-based control algorithm is developed for DTC and the proposed control scheme. Experimental results show qualitative improvement in performance in terms of reduction in torque ripple by 30%, fast dynamic response even at low speed and improvement in steady state characteristics.