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A direct-flux-vector-controlled scheme of induction generator has been proposed in this paper for future 42-V automobile application. The fundamental relationship between the rotating speed of the stator flux vector and torque is analyzed. A simple structure with only one proportional--integral (PI) controller is shown to implement the torque and flux controls adequately. By controlling the electromagnetic torque of the induction machine, the required dc-bus voltage can be well regulated within the 42-V PowerNet specifications. Fixed switching frequency and low torque ripple are obtained with space-vector modulation technique. Simulation and experimental results indicate that the proposed scheme provides a practical solution for an integrated starter alternator other than the widely applied field-orientedcontrol scheme. Index Terms--Direct-flux vector control (DFC), induction machine, integrated starter alternator (ISA), space-vector modulation (SVM), 42-V PowerNet.

This paper presents a new method of online estimation for the stator and rotor resistances of the induction motor for speed sensorless indirect vector controlled drives, using artificial neural networks. The error between the rotor flux linkages based on a neural network model and a voltage model is back propagated to adjust the weights of the neural network model for the rotor resistance estimation. For the stator resistance estimation, the error between the measured stator current and the estimated stator current using neural network is back propagated to adjust the weights of the neural network. The rotor speed is synthesized from the induction motor state equations. The performance of the stator and rotor resistance estimators and torque and flux responses of the drive, together with these estimators, are investigated with the help of simulations for variations in the stator and rotor resistances from their nominal values. Both resistances are estimated experimentally, using the proposed neural network in a vector controlled induction motor drive. Data on tracking performances of these estimators are presented. With this speed sensorless approach, the rotor resistance estimation was made insensitive to the stator resistance variations both in simulation and experiment. The accuracy of the estimated speed achieved experimentally, without the speed sensor clearly demonstrates the reliable and high-performance operation of the drive. Index Terms--Artificial neural networks (ANNs), induction motor drives, parameter identification, speed sensorlees vector control.

This paper presents a new observer for the rotor resistance of an indirect vector controlled induction motor drive using artificial neural networks supplemented by a fuzzy logic based stator resistance observer. The error between the rotor flux linkages based on a neural network model and a voltage model is back propagated to adjust the weights of the neural network model for the rotor resistance estimation. The error between the measured stator current and its corresponding estimated value is mapped to a change in stator resistance with a proposed fuzzy logic. The stator resistance observed with this approach is used to correct the rotor resistance observer using neural networks. The performance of these observers and torque and flux responses of the drive, together with these estimators, are investigated with the help of simulations. Both modeling and experimental data on tracking performances of these observers are presented. With this approach accurate rotor resistance estimation was achieved and was made insensitive to stator resistance variations both in modeling and experiment. Index Terms--Artificial neural networks (ANNs), fuzzy logic, induction motor drives, parameter identification.

This paper investigates problems associated with the implementation of a direct torque control (DTC) strategy for an interior permanent-magnet synchronous motor drive. The DTC technique is increasingly drawing attention because of elimination of current controllers and, hence, their inherent delays, and elimination of the rotor position sensor. The latter advantage perhaps is the main impetus for considering this new approach of torque control. Problems associated with this controller, namely, the offset in the current measurements, the stator resistance variation, and the requirement of initial rotor position are addressed in this paper. Ways of mitigating of these problems are also investigated in this paper. These are evaluated with modeling and experimental studies, results of which are also presented. Index Terms--Parameter estimation, permanent-magnet motors, position measurement, torque control.

A modified direct torque control (DTC) scheme for interior permanent magnet synchronous machine (IPMSM) is investigated in this paper, which features in very low flux and torque ripple and almost fixed switching frequency. It is based on the compensation of the error flux linkage vector by means of space vector modulation. Modeling and experimental results show that the flux and torque ripples are greatly reduced when compared with those of the basic DTC. With the new scheme, very short sampling time is not essential. All the advantages of the basic DTC are still retained. In addition, fixed switching frequency at different operating conditions becomes possible. The field-weakening control of this drive is also studied; an IPM DTC drive with a wider operation range and lower flux and torque ripple has been achieved experimentally. Index Terms--Drive, field weakening, interior permanent magnet synchronous machine, torque control.

This paper investigates a programmable cascaded low pass filter for the estimation of rotor flux of an induction motor, with a view to estimate the rotor time constant of an indirect field orientation controlled induction motor drive. Programmable cascaded low pass filters have been traditionally used in stator flux oriented vector control of the induction motor. This paper extends the use of this filter to estimate the rotor flux for the indirect field orientation control by generating rotor flux estimates from stator flux estimates. This is achieved by using a three-stage programmable cascaded low pass filter. The three-stage programmable cascaded low-pass filter investigated in this paper has resulted in excellent estimation of rotor flux in the steady-state and transient operation of an indirect field oriented drive. The estimated rotor flux data have also been used for the on-line rotor resistance identification with artificial neural network. Modeling and experiment results presented in this paper demonstrate this method of estimating rotor flux clearly. Index Terms--Induction motor drive, rotor flux, stator flux, steady-state, transient.

A novel direct torque control (DTC) scheme for an interior permanent magnet synchronous machine (IPMSM) is proposed in this paper, which features low torque and flux ripple and almost fixed switching frequency. The torque and flux ripples have been significantly reduced compared with those of the basic DTC reported in the literature. A speed estimation scheme is integrated with the proposed DTC scheme in order to achieve a fully sensorless high-performance IPMSM drive. Index Terms--Drive, permanent-magnet (PM) machine, torque control.

In direct torque control (DTC) scheme, the requirement of the continuous rotor position sensor and coordinate transformation is eliminated since all the calculation is done in stator reference frame. However, the DTC scheme requires the position sensor to determine the initial position of the rotor at starting. Elimination of the shaft-mounted position encoder is a very desirable objective in many applications since this sensor is often one of the most expensive and fragile components in the entire drive system. This paper presents a sensorless method of determining the initial rotor position of a direct torque controlled interior permanent magnet (IPM) synchronous motor drive. The method consists of injecting a high frequency voltage to the windings and examining the effects of the saliency on the amplitude of the corresponding stator current components. This method does not depend on the level of static load and on any motor parameters. The magnet polarity of the rotor at its initial position is also identified using the effect of saliency. Modeling and experimental results verify the effectiveness of the proposed method. Index Terms--Direct torque control, interior permanent magnet synchronous motor drive, sensorless initial rotor position estimation.

This paper presents the effect of magnetizing inductance on self-excitation. It also describes the loading analysis of an isolated induction generator, and how the operating frequency and generated voltage are affected by the change in operating slip value for regulated and unregulated rotor speed. Wind-powered self-excited induction generators have an input wind which is not controllable, but they can be set to operate within a given variation of speed. The experimental and simulated results for a dynamic generated voltage, frequency, and power are presented. The dynamic electromagnetic torque produced by the induction generator is also given. A dSPACE DS1102 digital signal processor card is used for data acquisition and for control of the driven speed. Index Terms--Induction generators, modeling, wind energy.

This paper reports results of further investigation of the so-called direct torque control (DTC) technique to an interior permanent magnet (IPM) synchronous motor drive. This torque control technique for IPM motors requires no dq-axes current controllers and coordinate transformation networks. A completely sensorless IPM motor drive with DTC, which uses a new speed estimator from the stator flux linkage vector and the torque angle, is presented. It is shown that including the torque angle in the estimation process results in a far more accurate transient speed estimator than what is reported in the existing literature. Index Term--Coordinate transformation, current control, direct torque control, interior permanent magnet motor, mechanical shaft sensor, rotor flux linkage, rotor reference frame, speed estimator, stator flux linkage.

Conventional model predictive control (MPC) for three-level active neutral point clamped converter (ANPC) utilizes weighting factors to achieve the optimal control of multiple control objectives in a single cost function. However, the selection of these weighting factors has an impact on the performance of the controlled objectives significantly. Tuning of weighting factors is usually tedious and lacks theoretical background. Moreover, the predictive and evaluation process for multiple objectives optimization have to be carried out by enumerating all admissible switching states within one loop. To simplify the complexity of this process and eliminate the effect of weighting factors, this paper proposes a cascaded predictive control scheme for a 3L-ANPC inverter fed induction machine (IM) drive. With the proposed approach, three separate cost functions for three control objectives, stator flux vector, neutral point voltage and device loss distribution are evaluated in a cascaded way, so that the optimization of these control objectives is performed independently. A 3L-ANPC inverter driven IM drive is studied in this paper to verify the effectiveness of the proposed algorithm. Experimental results in different operating conditions confirm that the proposed method achieves satisfactory steady-state and transient performances comparable to the conventional predictive control approach. The weighting factors used in the conventional method are eliminated and the computational effort is reduced by 68% compared to the conventional method without any sacrifice in the drive performance. [ABSTRACT FROM AUTHOR]

This paper presents a new control scheme for wide speed range operation of interior permanent magnet synchronous motor drives, where both torque and stator flux linkage are directly controlled. The proposed scheme possesses some attractive features when compared to the conventional current-controlled drives. Current controllers followed by pulsewidth modulation or hysteresis comparators and coordinate transformation are not used. This eliminates the delays through these networks and offers the possibility of dispensing with the rotor position sensor for the electronic commutator, if the initial rotor position is known only approximately. The scheme incorporates all the usual control regimes, such as the maximum torque per ampere operation in constant torque region, the flux-weakening region, and operates the drive within the voltage and current limits of the motor/inverter. The control scheme has been verified by simulation and experimental tests with a prototype interior magnet motor. This paper describes the scheme in detail, followed by results of its implementation. Index Terms - Direct torque control, field weakening, interior permanent magnet motor, maximum torque per ampere trajectory, stator flux linkage vector, stator voltage vectors, torque-angle characteristic, voltage-source inverter.

This paper describes a novel method of estimating the position of a plunger inside a solenoid. The solenoid is a single-phase variable reluctance actuator, with a highly nonlinear magnetic circuit. For the proposed method, position is estimated indirectly through the solenoid's incremental inductance in the high current region. It exploits the advantage that motional electromotive force (EMF) is negligible under normal operating condition. The incremental inductance is obtained from the rate of current rise of the pulse-width modualed (PWM) waveform, which in turn, is measured by a dedicated current rise measurement circuit. Position is estimated from a two dimensional look up table of incremental inductance and current. The method is simulated and then implemented on a typical industrial solenoid valve. Factors which affect the accuracy of the estimation and methods of overcoming them are also described in the paper.

Three-phase four-leg inverter is a well-known solution to handle unbalanced and nonlinear loading conditions in three-phase transformerless uninterruptible power supply applications. For such power converters, finite control set model predictive control (FCS-MPC) is considered as a promising control alternative due to its simplicity, fast dynamic response, and capability to include nonlinearities and constraints. However, the absence of modulator in FCS-MPC implementation leads to several shortcomings, such as higher load voltage total harmonic distortion (THD), large tracking error of control objectives, and variable switching frequency. Furthermore, the fourth leg operates with a higher average switching frequency than the other three main legs, which complicates the LC filter design. To overcome the aforementioned shortcomings, a new predictive duty cycle control is proposed in this article. Extensive experimental results are shown to verify that the proposed method can achieve enhanced steady-state performance with significant reduced load voltage THD and tracking error under different operating conditions, such as nonlinear single-/three-phase unbalanced load and single-phase short-circuit fault, while preserving the fast dynamic performance of FCS-MPC. Steady-state and dynamic performances of the proposed method are compared to FCS-MPC and double-vector MPC approaches to validate the superiority of the proposed scheme. [ABSTRACT FROM AUTHOR]

Modulated model predictive control (M2PC) approaches have been widely investigated owing to their improved steady-state performance and constant switching frequency operation. However, most of these methods either increase control complexity or cannot obtain optimal solutions under certain operating conditions such as lower modulation index and near the boundary of linear and over-modulation regions. To overcome these limitations, this study proposes a new modulated predictive current control technique based on a novel virtual vector synthesis. The optimal duty cycle is obtained by solving the optimisation problem defined by the cost function. To minimise the tracking error of the input current, a simple non-linearity compensation method for the converter is also demonstrated. The experimental results confirm that the proposed technique significantly reduces the steady-state error of the controlled objective and the ripples in the input current without sacrificing the transient performance compared to other existing M2PC methods. [ABSTRACT FROM AUTHOR]

The battery energy storage system has become an indispensable part of the current electricity network due to the vast integration of renewable energy sources (RESs). This paper proposes an optimal charging method of a vanadium redox flow battery (VRB)-based energy storage system, which ensures the maximum harvesting of the free energy from RESs by maintaining safe operations of the battery. The VRB has a deep discharging capability, long cycle life, and high energy efficiency with no issues of cell-balancing, which make it suitable for large-scale energy storage systems. The proposed approach determines the appropriate charging current and the optimal electrolyte flow rate based on the available time-varying input power. Moreover, the charging current is bounded by the limiting current, which prevents the gassing side-reactions and protects the VRB from overcharging. The proposed optimal charging method is investigated by simulation studies using MATLAB/Simulink. [ABSTRACT FROM AUTHOR]

The computational burden in Finite State Predictive torque control (FS‐PTC) increases with the number of voltage vectors and number of variables in the cost function. The conventional FS‐PTC for three level neutral‐point clamped voltage source inverter (3L‐NPC VSI) fed motor drive has a disadvantage of long execution time since all available vectors are evaluated in the prediction stage. This paper proposes a new method for reducing the number of voltage vectors from 27 to 17 in the prediction stage, which reduces the computational burden of conventional FS‐PTC. The performance of the proposed voltage selection method is investigated for an induction motor drive in terms of electromagnetic torque and stator flux responses (transient and ripple), total harmonic distortion of stator currents, neutral point voltage variations, average switching frequency reduction and robustness of the drive. Experimental results confirm that the execution time is reduced by 30% compared to conventional FS‐PTC while similar dynamic and steady‐state performances are preserved. [ABSTRACT FROM AUTHOR]

A finite-state predictive torque control system for a speed-sensorless induction motor drive supplied from a three-level neutral-point clamped inverter is proposed. For sensorless operation, the controller requires estimated speed and rotor/stator flux. In this study, the rotor speed and the rotor flux are estimated accurately by using an extended Kalman filter. Due to the large number of available voltage vectors, the control algorithm for a multilevel inverter-fed drive is computationally expensive. As a consequence, the controller requires longer execution time that yields worse torque, flux, and speed responses, especially at low-speed. In order to reduce the computational burden, a reduced number of voltage vectors for prediction and optimization in the control algorithm is proposed in this paper. The sign of the stator flux deviation and the position of the stator flux are predicted to lessen the number of voltage vectors tested. Experimental results illustrate that the proposed encoderless strategy can estimate the speed accurately over a wide speed range including field-weakening region while maintaining robustness and excellent torque and flux responses. [ABSTRACT FROM PUBLISHER]