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This work proposes a method to improve the estimation performance at standstill and low speed operations of an adaptive fuzzy logic speed‐sensorless field‐oriented control of an induction motor.

First, the speed estimation algorithm presented in Tursini et al., which it has been designed to consider constant speed operation, is modified in an attempt to reduce the estimation error. Second, the speed regulation by fuzzy logic controller (FLC) with fuzzy adapted gains (FAG) is proposed for speed regulation. The main features of the proposed algorithm are investigated and compared with those of the algorithm of (Tursini) considering different dynamic operating conditions.

Simulation results clearly show the performance of the proposed algorithm.

The proposed scheme is recommended for applications requiring robust speed control and field‐orientation even in the presence of some key parameter deviations.

This paper aims to analyze and investigate the performance of an improved fault detection and identification (FDI) method based on multiple criteria, applied to six-switch three-phase inverter (SSTPI)-fed induction motor (IM) drives under both single and multiple open insulated-gate bipolar transistors(IGBT) faults.

This paper proposes an advanced diagnostic method for both single and multiple open IGBT faults dedicated to SSTPI-fed IM drives considering five distinct faulty operating conditions as follows: a single IGBT open-circuit fault, a single-phase open-circuit fault, a non-crossed double fault in two different legs, a crossed double fault in two different legs and a three-IGBT open-circuit fault. This is achieved because of the introduction of a new diagnosis variable provided using the information of the slope of the current vector in (α-β) frame. The proposed FDI method is based on the synthesis and the analysis, under both healthy and faulty operations, of the behaviors of the introduced diagnosis variable, the three motor phase currents and their normalized average values. Doing so, the developed FDI method allows a best compromise of fast detection and precision localization of IGBT open-circuit fault of the inverter.

Simulation works, carried out considering the implementation of the direct rotor flux oriented control in an IM fed by the conventional SSTPI, have proved the high performance of the advanced FDI method in terms of fast fault detection associated with a high robustness against false alarms, against speed and load torque fast variations and against the oscillations of the DC-bus voltage in the case of both healthy and faulty operations.

This work should be extended considering the validation of the obtained simulation results through experiments.

Different from other FDI methods, which suffer from a low diagnostic effectiveness for low load levels and false alarms during transient operation, this method offers the potentialities to overcome these drawbacks because of the introduction of the new diagnosis variable. This latter, combined with the information provided from the three motor phase currents and their normalized average values allow a more efficient detection and identification of IGBT open-circuit fault.

The purpose of this paper is to develop a combined control (CC) technique based on the direct torque control (DTC) strategy and vector control (VC) method, to improve the overall performance of a three-phase induction machine (TPIM) drives.

The proposed control scheme includes a table-based DTC strategy in connection with a proportional-integral-sliding mode controller and pulse width modulation switching strategy. The control system has merits of DTC technique such as simple structure, less dependent on machine parameters, fast dynamic response and merits of VC technique such as high accuracy and constant switching frequency.

To validate the effectiveness of the proposed control system, simulation and experimental studies are carried out for a 0.75 kW TPIM in different operating conditions. The achieved results show the superiority of the proposed method in terms of fast dynamics and simple structure compared to the VC strategy and low speed and torque ripples and constant switching frequency compared to the DTC method.

Compared to the conventional CC strategies, the control law of the proposed method is based on DTC theory and modulation is established based on VC. In other words, the variable switching frequency which is one of the main disadvantages of the conventional CC strategies is rectified using the proposed CC scheme.