Search

In this paper, an extended-horizon predictive torque control (PTC) method is proposed with computationally efficient implementation. Predictive control with extended horizon brings important advantages compared to single-horizon methods, such as better steady-state performance, reduced current THD, and lower ripples in torque and stator flux. However, the computational burden is a serious obstacle because the required calculations rise exponentially with the extension of the prediction horizon. This is due to a high number of candidate voltage vectors and also predicting the values of several machine variables for these vectors. Different approaches are employed in this work to make the control method computationally tractable. A voltage vector reduction technique is utilised that significantly decreases the total number of enumerated vectors. Moreover, the stator current prediction is eliminated in the proposed method, based on the inherent features of the PMSM. The proposed method is experimentally implemented and its good performance and advantages are verified. [ABSTRACT FROM AUTHOR]

Severe vibrations and an increase in structural component fatigue failures have been observed on a freight locomotive class operating on a heavy haul route within South Africa. The root cause of these severe vibrations were investigated experimentally and it was found that polygonised wheels were cuasing these severe vibrations. A coupled mode of vibration exists in the traction system that is a combination of traction motor pitching and wheelset axle torsion. Harmonics and interharmonics are features of an AC motor controlled by a variable frequency drive (VFD) and were confirmed to cause resonance of the coupled vibration mode. Interharmonics are a function of the fundamental frequency ( f m ) of the VFD and the input AC frequency ( f g) supplied to the VFD. It was found by experimentation that the 5 f g − 7 f m interharmonic caused resonance of the coupled mode while the locomotive operated at 40 km/h. This running speed and frequency of vibration was found to fix the wavelength of a 20th order polygon on the wheels during approximately 11% of the locomotive's load hauling time. [ABSTRACT FROM AUTHOR]

Computational Self-awareness can improve performance, robustness, and adaptivity of a system. As a key element of self-awareness, observation quality is critical to gain a correct and comprehensive understanding of the system, its own state, and the environment. This is of more importance in systems, where contextual information plays a crucial role in the functional operation of the system. In this paper, the authors introduce confidence as a quality metric of observation and leverage it to improve the correct identification of states of a system. To evaluate the impact of this factor on the context-aware monitoring system at hand and to show the generality of the approach, we conduct a series of tests with and without confidence for condition monitoring of an industrial AC motor and an experimental water pipe system. Our experiments show that confidence not only improves the quality of system performance but also simplifies the system architecture and enhances its robustness. These findings support the recent initiatives of paying more attention to observation as an important factor in self-awareness and, consequently, the performance of systems. The proposed system facilitates condition monitoring of various industrial systems and is easily deployable as it does not require a deep domain knowledge. [ABSTRACT FROM AUTHOR]

This article studies the efficacy of a time-scale technique based on DWT for both stator and rotor asymmetries faults detection in WRIMs. The preliminary effort on the RAF detection in IMs relied mainly on the energy evaluation of a known low frequency bandwidth through DWT analysis. It was illustrated that the SCSVM and the IMSC are both good indicators for the RAF monitoring in steady state working conditions of WRIMs. In this work, it will be shown that in the case of any load variation, there is a time-varying DC component that may affect the energy evaluation criterion, resulting in a false alarm. Thus, an efficient method is proposed to estimate and then, to remove this DC component from both SCSVM and IMSC, before the energy evaluation through DWT analysis. Furthermore, by introducing a new frequency bandwidth, associated with SAF in the rotor current signature, this method can be extended to a universal slip independent stator and rotor asymmetries faults detection technique in WRIMs. The proposed approach is validated by experimental tests using a 7.5kW WRIM test rig. [ABSTRACT FROM AUTHOR]

This paper presents the improved control strategy with optimal switching scheme to improve the bidirectional converter's power flow control capability and to allow for different modes of operation in hybrid AC/DC microgrid. Also, this improved control strategy eliminates the need of PI controller for independent reactive power control. With the improvements in digital controllers, it is possible to implement complex control circuitry easily. The performance of bidirectional converter with improved control strategy is verified first in simulation environment and then on lab scale experimental set-up with the control circuit is implemented using hardware in loop in the real-time digital simulation platform. The simulation and experimental results for all the cases show that the controller is highly capable for power transfer between AC and DC grid with very fast response and also control reactive power without additional PI controller. Also, it maintains the current total harmonic distortion (THD) within standard limits. [ABSTRACT FROM AUTHOR]

This paper presents a new active approach in order to design a model-based fault-tolerant control (FTC) system for three-phase induction motors (IMs) subjected to mechanical faults caused by stator and rotor failures. In this approach, a nominal controller achieves control objectives in fault-free case. The main part of this approach is related to design a fault/state observer for simultaneous estimation of additive faults which model the mechanical faults and axial fluxes in any operating conditions. For trade-off between robustness and performance in the presence of uncertainties and faults, this fault/state observer design problem is reduced to a well-known mixedoptimisation problem by using polytopic linear parameter-varying approach. The FTC system consists of a nominal controller together with an observer which provides auxiliary inputs using the estimation of additive faults in order to compensate their undesirable effects on IM performance. The simulation results are shown to illustrate the effectiveness of the proposed approach to compensate the mechanical faults in IM. [ABSTRACT FROM AUTHOR]

Copyright of Automatika: Journal for Control, Measurement, Electronics, Computing & Communications is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A novel control algorithm devoted to remove undesired low-order current harmonics in AC motor drives is presented in this article. The proposed control algorithm combines a suitable multiple reference frame synchronous harmonic estimator and multiple reference frame vector control implementation to suppress the undesired harmonics contained in the motor stator currents. This control technique can handle positive-, negative-, and zero-sequence sets, keeping a satisfying dynamic behavior. The control technique has been evaluated by numerical simulations and experimentally tested on a permanent magnet synchronous motor drive. [ABSTRACT FROM PUBLISHER]

Phase-resolved partial discharge patterns of an inter-turn insulation specimen for a stator winding are investigated at different aging times under continuous square-wave pulse voltage. Comparing phase-resolved partial discharge patterns after square-wave pulse-voltage aging to those after sinusoidal-voltage aging, obvious independent clusters of discharge numbers occur with increases in the aging time of pulse voltage, whereas no similar phenomenon is observed after sinusoidal-voltage aging. Based on detailed analysis, partial discharge activity in a larger void is more intense, because the larger void has a larger memory effect, which is related to the number of residual charges. The enhanced electric field of the larger void accelerates the increase in void size. Furthermore, when the phase-resolved partial discharge patterns are measured under 50 Hz of sinusoidal voltage, since sinusoidal voltage creates less memory effect due to less residual charges, the corresponding partial discharges of different-sized voids occur at distinctly different phases of the sinusoidal voltage. For this reason, the independent clusters occur and become obvious with pulse-voltage aging. As a result, for pulse-width-modulated motors in industry, it is possible to evaluate the insulation condition through phase-resolved partial discharge patterns using 50 Hz partial discharge measurement. [ABSTRACT FROM AUTHOR]

In this article, the control technique of an AC variable-speed drive is presented using a modified direct torque control method. The AC motor of the drive is an induction motor, and the modified scheme of the direct torque control uses the space vector modulation technique to create the switching pattern of the inverter. The steady state of operation is investigated in depth as well as the dynamic performance of the system. The results of this modified control scheme are compared to the corresponding results of the classical direct torque control method, leading to the conclusion that the modified scheme is more robust and smoother in comparison to the classical one. [ABSTRACT FROM AUTHOR]

Copyright of Automatika: Journal for Control, Measurement, Electronics, Computing & Communications is the property of Taylor & Francis Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The model reference adaptive system is one of the methods for speed estimation of a sensorless induction motor drive. The model reference adaptive system comprises of tee blocks—the reference model, the adjustable model, and the adaptation mechanism. A proportional-integral controller is commonly used in the adaptation mechanism. In this article, an alternative structure of the adaptation mechanism is proposed. The model reference adaptive system with the proposed adaptation mechanism is simulated and experimentally validated tough a laboratory developed prototype. [ABSTRACT FROM AUTHOR]

Due to their robust structure, low and constant starting current, constant torque, and smooth and noiseless operation, small- and medium-sized power rating hysteresis motors are commonly employed in high-speed applications. However, hysteresis motors, in general, have a comparatively low power factor, efficiency, and torque density. In this article, a new structure, the coreless dual-rotor disc hysteresis motor, is introduced. Electromagnetic field analysis of the machine is performed, and its steady-state equivalent circuit is deduced. An algorithm employed in a computer simulation predicts the operating characteristics of the new machine. In comparison with common hysteresis machines, the superiority of the coreless dual-rotor disc hysteresis motor in regards to efficiency and power factor is revealed. Moreover, a sensitivity analysis is accomplished, and impacts of some structural parameters on the performance of the machine are illustrated. Simulation and a few experimental results for a prototype machine are given, and these validate the equivalent circuit and proposed model of the coreless dual-rotor disc hysteresis motor. [ABSTRACT FROM AUTHOR]

The d-q harmonic balance technique is utilized to extract the closed-form expressions for currents induced in the rotor cage of a line-start single-phase synchronous reluctance motor under steady-state conditions as a function of load angle and auxiliary winding run-capacitor value. The equations show a non-negligible amount of current flow in the rotor of the machine, even at synchronous speed operation; there is, therefore, an added I2R loss. The calculated I2R loss in the rotor d-axis circuit is higher and diminishes rapidly with increase in load angle, while the q-axis circuit loss increases slightly with load angle. A rapid increase in loss is also observed in both the d- and q-axes with increase in run-capacitor values. [ABSTRACT FROM AUTHOR]

This article presents the modeling and transient analysis of a 3-φ self-excited induction generator (SEIG) feeding an induction motor and a rectifier-controlled DC motor as dynamic loads with a static volt ampere reactive (VAR) compensator. It also deals with the necessary steps and guidelines to decide the parameters of a static VAR compensator (STATCOM) for a SEIG feeding an induction motor and controlled rectifier-fed DC motor loads. The STATCOM (an insulated gate bipolar transistor-based current-controlled voltage source inverter) provides the additional VAR required by the load and, thus, results in good voltage regulation. With consideration of the designed STATCOM parameters, the system is studied for switching of the static compensator and startup and loading of both an induction motor and a rectifier-fed DC motor. With the STATCOM, the performance of a SEIG feeding an induction motor and a controlled rectifier-fed DC motor is found commendable, as far as startup, voltage dip, and total harmonic distortion are concerned. [ABSTRACT FROM AUTHOR]

This article presents the design and implementation of a digital signal processor (DSP)-based induction generator controller (IGC) to regulate the voltage and frequency of a single-phase self-excited induction generator (SEIG), which employs a three-phase squirrel-cage induction machine that is suitable for the stand-alone power mode and employing an unregulated turbine, such as micro-hydro power generation. A three-phase induction machine can be used to generate single-phase supply at constant voltage and frequency if the electrical load is constantly maintained at its terminals. A prototype model of a single-phase SEIG is developed, such that the load on the SEIG remains constant despite a change in the consumer load. The transient behavior of the developed DSP-based SEIG-IGC system at different operating conditions, such as application and removal of static (resistive and reactive) and dynamic (single-phase induction motor) load, is investigated to demonstrate the capabilities of the proposed IGC. [ABSTRACT FROM AUTHOR]

This article models the simultaneous presence of broken rotor bars and static eccentricity (mixed fault) faults in a three-phase squirrel-cage induction motor using the time-stepping finite element method. A stator current signal is then used for the noninvasive diagnosis of mixed fault. The major problem in the analysis of an induction motor under mixed fault is the determination of the number of broken rotor bars and static eccentricity degree. Broken bars cause an asymmetrical rotor cage and influence the amplitude of the harmonic components. On the other hand, these harmonics are normally used to diagnose the static eccentricity degree independently. Also, static eccentricity leads to asymmetrical air gap flux and flux density distribution, which influence the amplitude of the harmonic components. Therefore, it is not easy to discriminate the contribution of each fault in the mixed-fault motor. Spectrum analysis of the stator current around the main component is used to diagnose the mixed fault and to determine the number of broken rotor bars. It is shown that this spectrum cannot be used to precisely detect the static eccentricity. Therefore, the spectrum analysis of current around the principle slot harmonic is used to diagnose the static eccentricity degree in the mixed-fault case. [ABSTRACT FROM AUTHOR]

A novel modulation technique for optimizing the performances of voltage source inverter feeding induction motor drives is presented. It is based on a variable frequency modulation technique, changing step-by-step the switching frequency of the power modules in order to achieve a reduction both of the switching losses and of the output voltage distortion. In addition, this technique is combined with the "single switch commutation" one, which allows to reduce the blank time imposition during the switches commutations. The proposed modulation strategy has been implemented by means of a digital modulator and several tests have been performed in order to verify its validity and feasibility. [ABSTRACT FROM AUTHOR]

A novel sliding mode observer for current-based sensorless speed control of induction motors is presented in this article. The control objective is to guarantee asymptotic tracking of prespecified references for speed and rotor flux magnitude, without sensors measuring the mechanical speed and the flux, and assuming to have some kind of uncertainties on the value of the rotor resistance. To this end, the proposed observer is designed by coupling a second-order sliding mode observer of the stator current with a nonlinear flux and speed observer, adaptive with respect to the rotor resistance. Estimation of unknown inputs is based on a different and original approach with respect to the widely used equivalent control-based techniques. As for the control aspects, in the present proposal, the problem of chattering, typical of sliding mode controllers, is made less critical since the derivative of the stator currents are used as discontinuous forcing actions, while the actual control signals are continuous, thus limiting the mechanical stress. [ABSTRACT FROM AUTHOR]

This paper presents the static eccentricity fault diagnosis using time stepping finite element (TSFE) method. In the previous publications on induction motor fault diagnosis by a finite-element method (FEM), steady-state analysis was proposed. White noise, large unbalanced magnetic pull (UMP), and even arc appear during the starting of a faulty induction motor. These phenomena particularly for large induction motor which have longer starting time are very important. In this paper, transient analysis of induction motor under fault is presented. In addition to the static eccentricity fault diagnosis, torque and speed due to the fault are also investigated. In order to show the significant effect of saturation on a faulty induction motor, simulations are carried out for a core with a constant permeability. The results of applying TSFE method and those obtained by application of winding function (WF) theory are compared. [ABSTRACT FROM AUTHOR]

Statistics show that 80% of faults are due to eccentricity in induction motors, promoting many research efforts still devoted to the eccentricity in these motors. This paper classifies different common faults in the stator and rotor. It then presents analysis techniques for faulty induction motors. Four more applied methods in the diagnosis and detection of faults in induction motors are investigated and critiqued. The finite difference method is introduced, and its drawbacks are noted. An equivalent magnetic circuit method is then discussed as a fast but less accurate method. The reduced accuracy of the latter method is due to neglect of the spatial harmonics, the relationship between these harmonics, and time harmonics, and particularly non-linearity of the magnetic materials. An analytical method of winding functions is investigated for the analysis of faulty induction motors. This method also neglects the spatial harmonics and their relationship with time harmonics, which could considerably influence the instant of the fault event. Therefore the finite element method (FEM) is used as a powerful numerical method for analysis of faulty induction motors. However, all the previously methods have the two following drawbacks: There is no modeling algorithm that compensates the base fault error data.There is no algorithm that could diagnose and distinguish between the levels of faults. Therefore, a combination of FEM and other methods (such as state-space, which can compensate the above-mentioned drawbacks) can be used as a precise, flexible and widely applicable technique for fault diagnosis of faulty induction motors. It is shown that this combination is implemented as an iterative process for prediction and analysis of induction motors. It concludes with some suggestions for future study. [ABSTRACT FROM AUTHOR]

A model reference adaptive fuzzy controller (MRAFC) consisting of a reference model and self-learning fuzzy logic controller and its application as a power system stabilizer (PSS) is described in this article. Off-line model identification is used to obtain a dynamic equivalent model for the synchronous machine with respect to the rest of the system. This model is used as the basis for defining a reference model for the generating unit. A fuzzy controller with self-learning capability is then used to adapt the system performance to track the reference model. The self-learning ability of the fuzzy controller is based on the steepest descent algorithm. The effectiveness of the proposed adaptive PSS based on this technique is demonstrated. Results obtained show improvement in the overall system damping characteristics using the proposed adaptive PSS. [ABSTRACT FROM AUTHOR]

To improve the efficiency of an induction motor (IM), an algorithm has been developed in terms of slip frequency. A discrete-time multi-input and multi-output (MIMO) optimal regulator is proposed to achieve the desired speed with efficiency optimization. Furthermore, a full-order observer is proposed to estimate rotor flux and magnetizing current because these states of IM are feedback to design the proposed controller. The performances of the efficiency optimized speed control and observer system have been verified by simulation. Regarding the simulation study, it can be stated that the proposed controller and observer system are suitable for the implementation of efficiency optimized speed control of IM. [ABSTRACT FROM AUTHOR]

In this article, the most common behavior of motor's motion is roughly classified into two categories: normal mode (NM) and continuous mode (CM). By the categories, we can concurrently transform the independent command data such as position, velocity and acceleration (å, V *, and D *) ordered by user into the dependent command signal (θ r *, ω r * r , and ω r *). Then we apply a cerebellar-model-articulation-controller (CMAC) as an auxiliary controller with a dominant proportional-integral (PI) controller to accomplish the position, velocity and acceleration motion control of a permanent-magnet synchronous motor (PMSM). At this time, we do not need to optimize the gain of the PI controller. In fact, when the system is stable, users can order any independent command data to control the behavior of a motor's motion. It is seen that the tracking error performance of the system with CMAC-based controller is always better than systems without it. Especially in the early period of the response, the tracking error performance of the system without CMAC-based controller is always larger than the systems with it. [ABSTRACT FROM AUTHOR]

In this article, a simplified thermal model for variable speed total enclosed fan cooled (TEFC) induction motors is proposed and experimentally verified. The thermal model is based on simple equations that are compared with more complex equations reported in literature. The proposed thermal model allows to predict the over temperature in the main parts of the motor, starting from the measured or the estimated losses in the machine. The description of the thermal model set up is reported in detail. Finally, the model is used to define the correct power derating for a variable speed PWM induction motor drive. In fact, if variable speed PWM drive employ general purpose self cooled induction motors, a torque derating is required due to motor efficiency and cooling effect reduction. This article presents in detail a procedure to preview the derating of self cooled induction motors, based on the proposed simplified thermal model, but accurate enough for practical applications. The obtained results ate experimentally verified on five standard industrial motors of the same series (4-7.5-15-30-55 kW, 4 poles, 380 V, 50 Hz). The previewed overtemperatures match the measured ones with an average accuracy better then 10% (absolute error less than ± 5° C). [ABSTRACT FROM AUTHOR]

A naturally commutated six-pulse cycloconverter working in the inverting mode is used to feed power to a single phase AC motor at 400 Hz. The motor is connected at the input side of the cycloconverter while the three-phase mains is connected at its output. Three-phase mains feeds power to the input side of the cycloconverter which is arranged as a tuned load at 400 Hz. The effect of the single-phase induction motor on system performance is discussed. The principle of voltage and frequency control for proper operation of the induction motor is presented. The results are experimentally verified. [ABSTRACT FROM AUTHOR]

Vector control scheme has been well adopted for higher performance applications of AC motor. Therefore, this paper presents an extensive development and investigation of vector control scheme for asymmetrical six-phase synchronous motor in a new two-axis (M–T) coordinate system. Phasor diagram has also been developed in a simplified way, followed by its implementation technique. Analytical results have been presented for four-quadrant operation of synchronous motor, employing the developed vector control scheme. In analytical control model, common mutual leakage reactance between the two winding sets occupying same stator slot has been considered. [ABSTRACT FROM PUBLISHER]