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Single-ended primary-inductor converter (SEPIC) was considered a good alternative to a DC-DC converter for photovoltaic (PV) systems. The SEPIC converter can operate with an input voltage greater or less than the regulated output voltage, or as a step-up or step-down. As a step-up converter, SEPIC boosts PV voltage to specific levels. However, gain limitation and voltage stress continue to reduce the efficiency of conventional SEPIC converters. Because of this, researchers created a modified SEPIC converter to improve performance. In this paper, six modified SEPIC converters were compared and evaluated. To compare fairly, all modified SEPIC converters are nonisolated and use a single switch. Power simulator (PSIM) software was used to simulate each converter with a BISOL BMO-250 PV module and maximum power point tracking (MPPT) P&O controller. The converter with the highest static voltage gain and lowest duty cycle has been identified. It results in up to ten times voltage increment with a 0.8-duty ratio. All topologies have the same voltage stress, with maximum and minimum values of 30.1 and 29.5 V, respectively. On the other hand, each topology produces different average efficiencies, with the highest and lowest efficiency at 99.5% and 97.2%, respectively. [ABSTRACT FROM AUTHOR]

Direct torque control (DTC) of induction machines is known to have a simple control structure with comparable performance to that of the field-oriented control technique. Two major problems that are usually associated with DTC drives are: 1) switching frequency that varies with operating conditions and 2) high torque ripple. To solve these problems, and at the same time retain the simple control structure of DTC, a constant switching frequency torque controller is proposed to replace the conventional hysteresis-based controller. In this paper, the modeling, averaging, and linearization of the torque loop containing the proposed controller followed by simulation and experimental results are presented. The proposed controller is shown to be capable of reducing the torque ripple and maintaining a constant switching frequency. Index Terms--AC motor drives, induction motor drives, torque control.

This paper presents an improved stator flux estimation technique based on a voltage model with some form of low-pass (LP) filtering. In voltage-model-based stator flux estimation, an LP filter is normally used instead of a pure integrator to avoid integration drift problem due to dc offset, noise, or measurement error present in the back electromotive force. In steady-state condition, the LP filter estimator will degrade the performance and efficiency of the direct torque control (DTC) drive system since it introduced magnitude and phase errors, thus resulting in an incorrect voltage vector selection. The stator flux steady-state error between the LP filter and a pure integrator estimator technique is derived and its effect on the steady-state DTC drive performance is analyzed. A simple method is proposed to compensate for this error which results in a significant improvement in the steady-state drive performance. Simulation based on this technique is given and it is verified by experimental results. Index Terms--Direct torque control, induction machines, stator flux, torque ripple.

This paper proposes a novel vector control method based on Rotor flux Field-Oriented Control (RFOC) for single-phase Induction Motor (IM) drives. It is shown that in a rotating reference frame, the single-phase IM equations can be separated into forward and backward equations with balanced structures. In order to accommodate for these forward and backward equations, a drive system consisting of two RFOCs that are switched interchangeably, is proposed. Alternatively, these two RFOC algorithms can be simplified as a single FOC algorithm. The analysis, controller design and simulation of the proposed technique showed that it is feasible for single-phase IM drive for high performance applications. [ABSTRACT FROM AUTHOR]

This paper proposes a novel flux observer based on Extended Kalman Filter (EKF) for high performance vector control of 3-phase Induction Motor (IM) drives under stator winding open-phase fault. The presented flux estimation combines the Indirect Rotor Field-Oriented Control (IRFOC) method. The rotor flux is obtained from two modified EKF with two different stator currents (forward and backward stator currents). The proposed technique can significantly reduce the DC-offset problem on the pure integrator associated with the basic IRFOC method. The Matlab simulation results confirm the validity of the proposed strategy. [ABSTRACT FROM AUTHOR]

This paper proposes a novel method for vector control of faulty three-phase Induction Motor (IM) drives based on Field-Oriented Control (FOC) method. The performance characteristics of the presented drive system are investigated at healthy and open-phase fault conditions. The simulation of the case study is carried out by using the Matlab/M-File software for a starconnected three-phase IM. The results show the better performance of the proposed drive system especially in reduction of motor speed and torque oscillations during open-phase fault operating. [ABSTRACT FROM AUTHOR]

An accurate model of balanced and unbalanced three-phase Induction Motor (IM) under balanced and unbalanced supply conditions based on Winding Function Method (WFM) is presented in this work. In this paper, the unbalanced condition in three-phase IM is limited to stator winding openphase fault. The analysis of presented models is shown in details which allow predicting the performance of 3-phase IM under different conditions. Computer simulations were obtained using the MATLAB software for a three-phase squirrel cage IM. MATLAB simulation results show that the oscillation of the speed and electromagnetic torque has increased considerably due to the open-phase fault in stator windings. [ABSTRACT FROM AUTHOR]

The industrial requirements for the control of an induction motor (IM) under fault conditions continue to be of attention, as evidenced by the majority current publications. The focus is on developments of control methods which can be used for faulty IM. A novel vector control technique based on stator field-oriented control (SFOC) for a 3-phase IM under open-phase fault is proposed in this paper. MATLAB simulation results are presented to illustrate the improvement in performance of the proposed algorithm. It has shown that for providing an appropriate algorithm to control faulty machine with one opened phase, the modification in the conventional controller is possible. [ABSTRACT FROM AUTHOR]