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Energy Conversion, IEEE Transactions on

Issue 2 • Date Jun 2002

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Displaying Results 1 - 22 of 22
  • Steady-state performance of synchronous generators with AC and DC stator connections considering saturation

    Page(s): 176 - 182
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (305 KB) |  | HTML iconHTML  

    Synchronous generators with AC and DC stator connections are widely used in systems where simultaneous AC and DC power supplies are needed. For these systems the voltage harmonic distortion of AC voltage, DC voltage ripple and DC voltage varying range are of special interest. Because of the commutation of rectifier and the saturation of magnetic circuit, the accurate calculation of voltage harmonic distortion and DC voltage varying range is comparatively difficult. This paper describes a mathematical model on the basis of multiloop method and FEM, which aims at calculating the steady-state characteristics and the voltage waveforms of AC winding accurately. With this method, the full synergic effects of space harmonics resulting from the magnetic circuit geometry, saliency, saturation, winding layouts, and slotting are included. The calculated results are compared with those of experiments View full abstract»

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  • Analysis of the induction machine parameter identification

    Page(s): 183 - 190
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (332 KB) |  | HTML iconHTML  

    This paper analyzes the numerical identifiability of the electrical parameters of induction machines. Formulations of the single and double-cage induction machine, with and without core-losses in both models, are developed. The impossibility of identifying all the parameters of these models when only external measurements (voltage, current, speed and torque) are used is shown. One proposed solution is the formulation of machine equations by using the minimum number of parameters (which are identifiable parameters). As an application example, the parameters of a double-cage induction machine are identified using steady-state measurements corresponding to different angular speeds View full abstract»

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  • A novel multilayer switched reluctance motor

    Page(s): 217 - 221
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (253 KB) |  | HTML iconHTML  

    The switched reluctance motor is a simple and robust machine, which has found application over wide power and speed ranges in different shapes and geometries. This paper introduces a new configuration for a high starting torque switched reluctance motor (SRM). This configuration allows more space for coil windings in small size motors with a high number of stator and rotor poles. It also presents a centrifugal switch mounted on the motor shaft for a sudden advancement of current-pulses relative to rotor position after reaching a preset motor speed in order to develop higher torque at starting. To evaluate the motor performance, two types of analysis, namely numerical techniques and an experimental study have been utilized. In the numerical analysis, due to the highly nonlinear nature of the motor, a finite element analysis is employed, and for the experimental study, a prototype motor has been built and tested. Finally, the prototype motor is compared with a conventional SRM of the same size. The calculated results compare favorably with the test results. In comparison with the conventional SRM, the proposed motor in this paper seems to be very promising View full abstract»

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  • Analytical closed-form solution of a space-vector modulated VSI feeding an induction motor drive

    Page(s): 191 - 196
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (278 KB) |  | HTML iconHTML  

    The paper presents the analysis of the time response of the stator and rotor currents in induction motor fed by space-vector pulse-width modulated voltage source inverter. This mathematical model uses the Laplace and modified Z-transform. The solution is made in two steps: (a) finding the Laplace transform of the stator voltage space vectors; and (b) finding the inverse transform of the load currents (original function) using the modified Z-transform. The solution is not dependent on the number of the pulses of the PWM pattern. All the analytical waveforms were visualized from the derived relations with the program MATHCAD. Experimental results prove the feasibility of the proposed mathematical model View full abstract»

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  • An induction machine model for predicting inverter-machine interaction

    Page(s): 203 - 210
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (306 KB) |  | HTML iconHTML  

    The conventional qd induction motor model typically used in drive simulations is very inaccurate in predicting machine performance, except perhaps for the fundamental component of the current and the average torque near rated operating conditions. Predictions of current and torque ripple are often in error by a factor of two to five. This work sets forth an induction machine model specifically designed for use with inverter models to study machine-inverter interaction. Key features include stator and rotor leakage saturation as a function of current and magnetizing flux, distributed effects in the rotor circuits, and a highly computationally efficient implementation. The model is considerably more accurate than the traditional qd model, particularly in its ability to predict switching frequency phenomena. The predictions of the proposed model are compared with those of the standard qd model and to experimental measurements on a 37 W induction motor drive View full abstract»

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  • Synthesis of high performance PM motors with concentrated windings

    Page(s): 248 - 253
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (287 KB)  

    The windings concentrated around the teeth offer obvious advantages for the electrical machines with radial air-gap, because the volume of copper used in the end-windings can be reduced. The Joule losses are decreased, and the efficiency is improved. These machines are still limited to applications of sub-fractional power and they generally present a reduced number of phases. In the three-phase machines, the concentrated winding is too often restricted to a winding with a short pitch of 120 electrical degrees, i.e., to a winding with performances reduced compared to the traditional structures. But there is a significant number of three-phase structures which can support a concentrated winding if the number of poles is increased. In this article, the authors present a synthesis of the structures of three-phase machines with concentrated windings. (1) In the first part, the structures with a regular distribution of the slots are presented. A systematic method is proposed to determine the windings and the performances are discussed. (2) In the second part, the authors present original structures of three-phase machines with concentrated windings which use an irregular distribution of the slots. A specific method to identify these structures is described, and a comparative analysis of the performances of the original and traditional structures is performed by using a field calculation software View full abstract»

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  • A space vector modulation algorithm for torque control of inverter fed induction motor drive

    Page(s): 222 - 228
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB) |  | HTML iconHTML  

    After a short review of the vectorial torque control (VTC) strategy, the design and setup of a dedicated modulation hardware unit is described in detail. Experimental comparisons with traditional induction motor control techniques fully confirm the validity of the proposed system View full abstract»

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  • Automatic generation control of a wind farm with variable speed wind turbines

    Page(s): 279 - 284
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (257 KB) |  | HTML iconHTML  

    Wind farms are considered to be negative loads from the point of view of a utility manager. Modern variable-speed wind turbines offer the possibility for controlling active and reactive power separately. This paper presents a new integrated control system of a wind farm according to the utility manager's requirements. This control system is based on two control levels: a supervisory system controls active and reactive power of the whole wind farm by sending out set points to all wind turbines, and a machine control system ensures that set points at the wind turbine level are reached. The system has been validated by numerical simulation using data from a wind farm with 37 variable-speed wind turbine situated in the North of Spain. An automatic generation control of these characteristics promises improved performance of the system and a better grid integration of the wind energy without significant extra costs View full abstract»

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  • Propagation of flicker in electric power networks due to wind energy conversions systems

    Page(s): 267 - 272
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (246 KB) |  | HTML iconHTML  

    Wind energy conversion systems (WECS) produce fluctuating output power, which may cause voltage fluctuations and flicker. Flicker assessment in networks may be difficult since its evaluation requires long computing time and special procedures to calculate the flicker severity index, Pst. In this paper, a frequency domain method to study flicker propagation is presented. This method is based on propagation of frequency components from WECS output currents throughout the grid. In this way, a fast flicker analysis in a network of any size can be performed. Also, an algorithm for flicker measurement in the frequency domain, which allows Pst calculation, is proposed. Several study cases have been performed, and results have been compared with time domain simulations, showing good agreement between them View full abstract»

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  • Control-based reduction of pulsating torque for PMAC machines

    Page(s): 169 - 175
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (338 KB) |  | HTML iconHTML  

    Control methods in torque pulsating reduction for surface-mounted permanent magnet motors are discussed in this paper. The pulsating torque is a consequence of the nonsinusoidal flux-density distribution caused by the interaction of the rotor's permanent magnets with the changing stator reluctance. The proposed control method is estimator based. To assure parameter convergence, Lyapunov's direct method is used in estimator design for the flux Fourier's coefficients. A novel nonlinear torque controller based on flux/torque estimate is introduced to reduce the influence of the flux harmonics. The influence of the cogging torque is considerably reduced at lower motor speed using the internal model principle and adaptive feedforward compensation technique. The overall control scheme and experimental results are also presented View full abstract»

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  • Questionable system grounding practices at nuclear power plants

    Page(s): 295 - 298
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (166 KB) |  | HTML iconHTML  

    A number of questionable system grounding practices have been identified at nuclear power plants. These practices could result in unforeseen degradation of the ac Class 1E Power System. (Class 1E is the safety classification of the electrical systems and equipment utilized to mitigate accidents at nuclear power plants.) The paper provides an overview of system grounding with emphasis on the challenges faced with ungrounded and high-resistance grounded systems. It explains how design deficiencies are to be treated with respect to the single failure criterion, then gives a few examples of questionable system grounding practices that have been observed at nuclear power plants in the United States, categorizing these as potential design deficiencies View full abstract»

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  • Performance enhancement of an induction motor by secondary impedance control

    Page(s): 211 - 216
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (267 KB) |  | HTML iconHTML  

    The paper demonstrates the use of nonresistive secondary control of an induction motor to improve efficiency, power factor and torque. A mathematical algorithm is presented to predict the control requirements in terms of secondary capacitance. The required secondary capacitance is implemented by a novel electronic switching technique that effectively increases the value of the used capacitor. This overcomes the high-capacitance demand and provides a feasible solution. Experimental verification is presented in the results obtained from a small induction motor drive View full abstract»

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  • Techniques to control the electricity generation in a series hybrid electrical vehicle

    Page(s): 260 - 266
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (276 KB) |  | HTML iconHTML  

    In a series hybrid electric vehicle (SHEV), an electric generator feeds a DC busbar (containing an electrochemical accumulator), which, in turns, feeds the vehicle traction system. A very important part of the vehicle is its control system, which has to maximize the vehicle efficiency while keeping the emissions within predetermined limits. To attain this goal, it can act in two ways: (1) it can switch the electric generator ON or OFF, and (2) when in the ON state, it can impose a given power to be delivered. To choose the control actions to perform it needs (a) an algorithm to understand the behavior of the battery (determine the state-of-charge, maximum power, losses) and (b) an algorithm to make some forecast of the system load (i.e., the power required in the future of the trip, as a function of time). This paper discusses the main problems that arise when trying to synthesize the control system of the vehicle, taking into account issues (a) and (b). Some lab tests are also presented in which some of the proposed control techniques are experimentally checked View full abstract»

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  • Identification of synchronous machine parameters using load rejection test data

    Page(s): 242 - 247
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (225 KB) |  | HTML iconHTML  

    This work shows a computational methodology for the determination of synchronous machines parameters using load rejection test data. By machine modeling one can obtain the quadrature parameters through a load rejection under an arbitrary reference, reducing the present difficulties. The proposed method is applied to a real machine View full abstract»

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  • A rule-based acceleration control scheme for an induction motor

    Page(s): 254 - 259
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (301 KB)  

    This paper presents a rule-based acceleration control scheme that aims to give an inverter-fed induction motor excellent dynamic performance. In every time interval of the control process, the acceleration increments produced by two different voltage vectors are compared, yielding one optimum stator voltage vector which is selected and retained. The online inference control is built using a rule-based system and some heuristic knowledge about the relationship between the motor voltage and acceleration. Because evaluation of integrals is not required and the motor parameters are not involved, the new controller has no accumulation error due to the integrals as in the conventional vector control schemes and the same controller can be used for different motors without modification View full abstract»

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  • Investigation of back-to-back starting of pumped storage hydraulic generating units

    Page(s): 273 - 278
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (220 KB) |  | HTML iconHTML  

    In the present paper, the procedure of back-to-back starting of pumped-storage hydraulic generating units is investigated and analyzed. The results from simulation as well as from real on-site measurements are presented and compared for a case study of a Greek power station. Main parameters influencing this phenomenon are analyzed, and information is given on the physical laws underlying the process. In particular, the effects of excitation and gate valve opening procedure are discussed, along with the torque-speed characteristic of the driving machine. Guidance is developed for the proper selection of the main parameters for a successful start View full abstract»

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  • Model reference neural network controller for induction motor speed control

    Page(s): 157 - 163
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (273 KB)  

    This paper proposes a novel robust speed control method for induction motor drives based on a two-layered neural network plant estimator (NNPE) and a two-layered neural network PI controller (NNPIC). The NNPE is used to provide a real-time adaptive estimation of the unknown motor dynamics. The widely used projection algorithm is used as the learning algorithm for these neural networks to automatically adjust the parameters of the NNPIC and to minimize the differences between the motor speed and the speed predicted by the NNPE. The simulation and experimental results demonstrate that the proposed robust control scheme can improve the performance of an induction motor drive and reduce its sensitivity to parameter variations and load disturbances View full abstract»

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  • Investigation of torsional instability, bifurcation, and chaos of a generator set

    Page(s): 164 - 168
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (260 KB) |  | HTML iconHTML  

    In this paper, the nonlinear phenomenon known as Hopf bifurcation, chaos and asynchronous operation of a simple power system are explored. Firstly, taking into account the nonlinearity of the generator shaft and the interaction of mechanics and electrics in the generator sets, the authors obtain a transient model by combining Park equations and mechanics equations. Then the Hopf bifurcation, period-doubling bifurcation and chaos caused by too large a line resistance are investigated with nonlinear mode and Floquet theory. The bifurcation figure of the system is also given. Further study shows that the chaos attractor breaks up into asynchronous operation when the resistance becomes larger. This way of loss-of-stability is different from that caused by loss-of-excitation View full abstract»

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  • Steady-state characteristics of synchronous machine-line-commutated converter systems

    Page(s): 234 - 241
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (334 KB) |  | HTML iconHTML  

    A steady-state model of a synchronous machine-line-commutated converter pair is obtained from a dynamic average-value model of the system that accurately accounts for subtransient saliency of the machine. This steady-state model is comprised exclusively of linear and nonlinear algebraic equations that relate key variables of the system. Various algorithms for solving these equations to generate characteristics that relate two or three of these variables at a time are described. Specific characteristics that are illustrated include machine torque versus firing angle for constant DC current and DC voltage versus DC current for constant firing angle View full abstract»

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  • Simplified steady-state model of an SCR-inverter-based load-commutated commutatorless series motor

    Page(s): 197 - 202
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (255 KB) |  | HTML iconHTML  

    This paper presents a simplified analytical model of a silicon-controlled-rectifier based, load-commutated inverter driven, commutatorless series motor to predict its speed-current, torque-current and torque-speed characteristics. The model has been formulated, keeping in view the steady state equivalent circuit of a conventional DC series motor. The proposed analytical expressions relating torque and current with speed are found to follow an inverse law and that relating torque and current is found to be parabolic, as is expected in a "series" machine. The drive has been implemented, loaded with a DC generator and experimentally similar characteristics have been obtained, as predicted by the analytical model. The characteristics obtained experimentally are seen to follow the ones, predicted by the analytical model closely View full abstract»

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  • In-wheel permanent-magnet brushless DC motor drive for an electric bicycle

    Page(s): 229 - 233
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (247 KB) |  | HTML iconHTML  

    This paper presents the design of an axial-field PM brushless DC motor drive for use on an electric bicycle. Details of the motor and the electronic converter are given. Performance analysis using the finite element method is briefly discussed. A prototype motor was constructed for verifying the actual performance. Good correlation between the theoretical and experimental results hs been obtained. Test results confirmed the feasibility of the proposed motor design View full abstract»

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  • Dynamic multiphysics model for solar array

    Page(s): 285 - 294
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (511 KB) |  | HTML iconHTML  

    An approach to model the solar cell system with coupled multiphysics equations (photovoltaic, electro-thermal, direct heating and cooling processes) within the context of the resistive-companion method in the Virtual Test Bed computational environment is presented.. Appropriate across and through variables are defined for the thermal terminal of the system so that temperature is properly represented as a state variable, rather than as a parameter of the system. This allows enforcement of the system power conservation through all terminals, and allows simultaneous solutions for both the electrical potentials and the system temperature. The thermal port built accordingly can be used for natural thermal coupling. The static and dynamic behaviors of the solar array model based on the approach are obtained and validated through comparison of simulation results to theoretical predictions and other reported data. The electro-thermal modeling method developed here can be generally used in the modeling of other devices, and the method to define the across and through variables can also be generalized to any other interdisciplinary processes where natural coupling is required View full abstract»

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Aims & Scope

The IEEE Transactions on Energy Conversion includes in its venue the research, development, design, application, construction, installation, operation, analysis and control of electric power generating and energy storage equipment (along with conventional, cogeneration, nuclear, distributed or renewable sources, central station and grid connection). The scope also includes electromechanical energy conversion, electric machinery, devices, systems and facilities for the safe, reliable, and economic generation and utilization of electrical energy for general industrial, commercial, public, and domestic consumption of electrical energy.

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Meet Our Editors

Editor-in-Chief
Juri Jatskevich
University of British Columbia