This paper proposes a novel direct torque control (DTC) strategy for induction motor (IM) drives fed by a four-switch three-phase inverter (FSTPI). The introduced strategy is based on the emulation of the operation of the conventional six-switch three-phase inverter (SSTPI). This has been achieved thanks to a suitable combination of the four unbalanced voltage vectors intrinsically generated by the FSTPI, leading to the synthesis of the six balanced voltage vectors of the SSTPI. This approach has been adopted in the design of the vector selection table of the proposed DTC strategy which considers a subdivision of the Clarke plane into six sectors. Simulation results have revealed that, thanks to the proposed DTC strategy, FSTPI-fed IM drives exhibit interesting performance. These have been experimentally validated and compared to the ones yielded by the Takahashi and the basic DTC strategies dedicated to the SSTPI and to the FSTPI, respectively.

Currently, road vehicles are more equipped with permanent magnet synchronous motors. Particularly interesting are brushless dc (BLDC) motors, which, due to their inherently sensorless operation, are considered as viable candidates in large-scale production industries such as the automotive one. Within this trend, this paper deals with the synthesis and implementation of a novel direct torque control (DTC) strategy dedicated to the control of BLDC motor drives. Compared with the most recent and highly performed DTC strategy, the proposed one offers improved reliability due to the achievement of balanced switching frequencies of the inverter upper and lower insulated-gate bipolar transistors, on one hand, and the reduction in the average value of the motor common mode voltage, on the other hand. Furthermore, the torque ripple is significantly damped during sector-to-sector commutations using a three-level hysteresis torque controller. An experientially based comparative study of the most recent and highly performed DTC strategy from one side and the introduced one from the other side clearly highlights the potentialities exhibited by the latest one.

This paper deals with a new direct torque control (DTC) strategy based on the bus-clamping technique dedicated to induction motor drives. The proposed strategy consists in the synthesis of two vector selection tables suitably arranged considering the bus-clamping technique. Such synthesis depends on the rotation direction of the stator flux vector. The resulting DTC strategy leads to clamp each motor phase during 60° interval in every half cycle of the reference stator flux vector. Therefore, a reduction of the inverter switching losses is gained. Furthermore, it has been found that the proposed DTC strategy offers a lower harmonic distortion of the motor phase currents and a higher capability to operate at low levels of the dc-bus voltage, which could be of interest for electric vehicle (EV) and hybrid electric vehicle (HEV) applications. These performances are confirmed by simulation and validated by experiments.

This paper deals with an investigation of the steady-state and transient performance of the direct rotor flux-oriented control (RFOC) strategies implemented in symmetrical two-phase induction motors (2PIMs). Such an investigation is structured within a comparison study considering: 1) the case of a two-leg voltage source inverter (B4-inverter), and 2) the case of a three-leg voltage source inverter (B6-inverter), in the stator of the 2PIM. Following a presentation of both drives, the principle of the RFOC is briefly recalled. Then, a special attention is paid to the implementation of the direct RFOC on current-regulated B4- and B6-inverters. The control of the power switches is achieved by two two-level hysteresis regulators in the B4-inverter rather than three in the B6-inverter. Initiated by a simulation-based analysis of the selected steady-state features of both 2PIM drives under direct RFOC strategies, the comparison study is then extended to a deep experimental investigation of the steady-state operation with emphasis on the dc-link capacitor voltages, the stator line-to-line and phase voltages, stator phase currents, the rotor flux, and the electromagnetic torque. The established results reveal three major limitations of the B4-inverter fed 2PIM drive, such as: 1) unbalanced dc-link capacitor voltages at low speeds; 2) a reduced speed range due to the low level of the phase voltages; and 3) an injection of harmonics due to the d-q transformation. While the B6-inverter exhibits balanced dc-link capacitor voltages in the total constant torque region with higher ripple of the stator phase currents and of the electromagnetic torque, the experiment-based comparison is achieved by an investigation of the dynamic behaviors of both drives under step- and ramp-shaped reversals of the reference speed. It highlights the poor dynamic behavior of the B4-inverter fed 2PIM drive under both shapes of speed reversal.

Purpose – The purpose of this paper is to analyze the performance of a new direct torque control (DTC) strategy dedicated to four-switch three-phase inverter (FSTPI)-fed induction motor drives with extended speed range. Design/methodology/approach – The approach is based on the synthesis of a suitable vector selection table in order to reduce torque ripple. The performance analysis is carried out based on three criteria: the total harmonic distortion; the switching loss factor; and the quality factor. Findings – It has been clearly shown that the introduced DTC strategy offers high performance during both transient and steady-state operations of the FSTPI-fed induction motor drive, which are almost the same as those yielded by the Takahashi DTC strategy implemented in the same motor fed by a conventional six-switch three-phase inverter (SSTPI). Research limitations/implications – The work should be extended by an experimental validation of the simulation results. Practical implications – The established results open up crucial benefits from the point of view of cost-effectiveness and volume-compactness of induction motor drives especially in large-scale industries such as the automotive, where electric and hybrid propulsion systems are currently regarded as an interesting alternative to substitute or to assist the thermal propulsion systems. Originality/value – The paper presents the implementation of a dedicated DTC strategy in FSTPI-fed induction motor drives with extended speed range. The proposed DTC strategy offers interesting performance compared with that yielded by the Takahashi DTC strategy implemented in the same motor fed by an SSTPI.