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This article presents a novel Direct Field-Oriented Control (DFOC) strategy for Fault-Tolerant Control (FTC) of wye-connected 3-Phase Induction Machine (3-PIM) drives under the stator winding open-phase failure. In the proposed control strategy, instead of flux measurement, an Extended Kalman Filter (EKF) for flux estimation is used. The introduced controller with minor modifications can be used during normal and stator winding open-phase failure conditions. With the proposed DFOC system, the speed and torque pulsations that normally happen during the open-phase failure can be reduced. The performances of the proposed EKF-based DFOC strategy and the conventional control strategy for a faulted machine using simulations and experiments under different operation conditions are compared. Simulation and experimental results demonstrated an important improvement in speed and torque pulsations through this type of fault. Results also confirmed the superiority of the proposed EKF-based DFOC scheme over the conventional control scheme to balance the faulted machine phase currents.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

The present study aims to propose an indirect field-oriented control (IFOC) strategy for star-connected three-phase induction machine (SCTPIM) drives against singlephase open-circuit fault. In the proposed IFOC method, transformation matrices (TMs) are applied to the faulty SCTPIM equations. Based on the results, the asymmetrical equations of the faulty SCTPIM can be transformed into symmetrical equations by using these matrices. The symmetrical equations have structures which are similar to healthy SCTPIM equations. Thus, a midfield IFOC strategy could be shared during both normal and open-phase fault operations. The performance of the proposed control system was confirmed based on the simulations and experiments for a vector controlled 0.75 kW SCTPIM drive. The results confirmed the effectiveness of the introduced controller in the speed and torque ripples decreasing of the faulty SCTPIM and eliminating the unbalances in the faulty SCTPIM currents.

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Background: 3ϕ Induction Machine (IM) drives are broadly used in different industrial applications. During failure conditions, 3ϕ IM drive systems cannot continue its optimal performance. Aims: The present study presents a method for indirect rotor field-orientated control (IRFOC) of star-connected 3ϕ IM drives during open-phase failure (OPF) condition. In addition, in this study the particle swarm optimization algorithm was used to determine the coefficients of proportional-integral (PI) controllers in the OPF mode. Materials & Methods: In the proposed method, two unbalanced currents and voltage rotational matrices are utilized to change the asymmetrical structure of the faulty 3ϕ IM equations to the equations with a symmetrical structure. Using these matrices, the speed control of the faulty 3ϕ IM can be realized with minor changes in the conventional IRFOC structure including control parameters, transformation matrices, and coefficients of PI controllers. Results: Experimental results were presented during various operating conditions on a 1 HP star-connected 3ϕ IM drive system. Discussion: The experimental tests in different operating conditions showed good performances of the proposed control system during both the steady-state and the transient periods. Conclusion: The proposed control method exhibited a significant improvement in reducing the speed, torque, and flux oscillations, compared to the

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