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Energy Conversion, IEEE Transactions on

Issue 2 • Date June 2011

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Displaying Results 1 - 25 of 37
  • Table of contents

    Page(s): C1 - C4
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    Freely Available from IEEE
  • IEEE Transactions on Energy Conversion publication information

    Page(s): C2
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    Freely Available from IEEE
  • Modeling of Salient-Pole Wound-Rotor Synchronous Machines for Population-Based Design

    Page(s): 381 - 392
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1259 KB) |  | HTML iconHTML  

    In recent years, population-based methods (evolutionary algorithms, particle swarm methods, etc.) have emerged as an effective tool for component and system design. Although relatively straightforward to apply, to capitalize on their potential, one must be able to explore a large design space. Herein, a magnetic equivalent circuit model is described to enable large-design-space exploration of salient-pole wound-rotor synchronous machine drive systems. Specifically, the model has been derived to evaluate machines with an arbitrary number of poles, stator slots (integer slots/pole/phase), winding layout, magnetic material, and a wide range of stator and rotor geometries. In addition, the model and solution technique have been structured to minimize the computational effort. An important attribute of the model is that saturation is handled with relatively few iterations and without the need for a relaxation factor to obtain convergence. View full abstract»

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  • An Adaptive Dynamic Matrix Control With Fuzzy-Interpolated Step-Response Model for a Drum-Type Boiler-Turbine System

    Page(s): 393 - 401
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (984 KB) |  | HTML iconHTML  

    In this paper, dynamic matrix control (DMC) is made adaptive for a boiler-turbine system by using online interpolated step-response model (SRM) with fuzzy inference. A plant is described as an SRM in a conventional DMC. However, a nonlinear boiler-turbine system cannot be effectively modeled as a single SRM. In this paper, the plant is modeled with nine SRMs at various operating points, and then they are interpolated with fuzzy inference rules. The interpolation is performed at every sampling step online in order to find the best SRM for an arbitrary operating point. Therefore, the proposed adaptive DMC can achieve a bumpless control for nonlinear systems. Simulation results show satisfactory result with a wide range operation of a boiler-turbine system. View full abstract»

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  • Voltage and Frequency Controllers for an Asynchronous Generator-Based Isolated Wind Energy Conversion System

    Page(s): 402 - 416
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3638 KB) |  | HTML iconHTML  

    This paper presents a state of art on voltage and frequency controllers (VFCs) for isolated asynchronous generators (IAGs) for standalone wind energy conversion systems. In wind turbine-driven IAG, magnitude and frequency of the generated voltage vary because of varying consumer loads and wide fluctuation in wind speeds. Therefore, new types of VF controllers based on a voltage source converter along with a battery energy storage system are proposed to maintain the voltage and frequency of IAG constant at varying wind speeds and varying consumer loads. A set of new VF controllers is designed and their performance is simulated in the MATLAB environment using Simulink and Sim-Power System toolboxes to study their behavior for standalone wind power generation. View full abstract»

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  • Design and Analysis of a High-Gain Observer for the Operation of SPM Machines Under Saturation

    Page(s): 417 - 427
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (822 KB) |  | HTML iconHTML  

    This paper presents a high-gain observer of the rotor position for the control of surface permanent magnet synchronous machines under loaded conditions, e.g., saturation. Determining the rotor flux position of permanent magnet AC machines under no load is simpler, since its flux and rotor position coincide. However under load and in the presence of saturation in particular, the flux is comprised of two components: one due to the rotor magnets and the other due to the stator current. This causes the magnetic axis to shift from the rotor position, which in turn causes an error in a control algorithm that uses conventional rotor position estimation. This paper characterizes this error through a nonlinear model of the machine and finite element analysis. Design and analysis of a general position observer algorithm for PMAC machines accounting for saturation is presented, along with its implementation for a control methods using back EMF measurement and high-frequency Injection. Experimental results validating the nonlinear model of the machine, existence of the saturation-induced error, and performance of the proposed observer are also given. View full abstract»

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  • Control and Interfacing of a Grid-Connected Small-Scale Wind Turbine Generator

    Page(s): 428 - 434
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (730 KB) |  | HTML iconHTML  

    An ac/dc/ac power converter is an important device used to extract power from variable speed permanent magnet wind generators and feed it into the grid. This paper describes how these converters incorporate maximum power point tracking based on its power feed to the grid at different wind speeds. Using the permanent magnet generator voltage, grid current, and grid voltage samples, the proposed system achieves an enhanced dynamic behavior. This feature effectively prevents the grid from “boost” charging the dc side of the H-bridge inverter at the start of operation. Since small wind turbines normally do not have expensive pitch control mechanisms, a thyristor-based “dump-load circuit” is employed to protect the turbine from high wind speed operation when disconnected from the grid. The thyristor controller also protects the inverter from high dc voltage input from the wind generator at high wind speed. Preliminary results are included using a laboratory 2-kW prototype converter. View full abstract»

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  • Recurrent Neural Network-Based Modeling and Simulation of Lead-Acid Batteries Charge–Discharge

    Page(s): 435 - 443
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1039 KB) |  | HTML iconHTML  

    This paper presents the main experiences and results obtained about the problem of the lead-acid battery modeling and simulation. A nonlinear mathematical model is presented as well as results of neuroprocessing of the charge-discharge experimental and simulated data. Recurrent neural networks were used to provide a state-of-charge observer and model parameter estimation and tuning. The simulation results are compared with those obtained by extensive lab tests performed on different batteries used for electric vehicle and photovoltaic application. View full abstract»

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  • Improved Superconducting Magnetic Energy Storage (SMES) Controller for High-Power Utility Applications

    Page(s): 444 - 456
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2133 KB) |  | HTML iconHTML  

    Superconducting magnetic energy storage (SMES) systems are getting increasing interest in applications of power flow stabilization and control in the transmission network level. This trend is mainly supported by the rising integration of large-scale renewable energy power plants into the high-power utility system and by major features of SMES units. In a SMES system, the power conditioning system (PCS) is the crucial component for controlling the power exchange between the superconducting coil and the ac system. The dynamics of the PCS directly influences the validity of the SMES in the dynamic control of the power system. This paper describes a novel PCS scheme of SMES to simultaneously perform both active and reactive power flow controls. Moreover, a detailed model of the SMES unit is derived and a three-level control scheme is designed, comprising a full decoupled current control strategy in the d-q reference frame with a novel controller to prevent PCS dc bus capacitors' voltage drift/imbalance. The dynamic performances of the proposed systems are fully validated by computer simulation. View full abstract»

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  • Multiphysic Modeling of a High-Speed Interior Permanent-Magnet Synchronous Machine for a Multiobjective Optimal Design

    Page(s): 457 - 467
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1121 KB) |  | HTML iconHTML  

    High-speed electric drive design is concerned with paying particular attention to thermal and mechanical design of the machine. Therefore, this paper proposes a multiphysic modeling of an interior permanent-magnet synchronous machine (IPMSM) dedicated to high speed, including magnetic, electric, thermal, and mechanical aspects. The proposed analytical models are verified using finite-element (FE) computations. These models are then subjected to a multiobjective optimization-based on genetic algorithm-to design an IPMSM for a high-speed compressor application that develops 30 kW at 20 000 r/min. The design is formulated as a constrained optimization problem consisting of maximizing the machine efficiency while minimizing its weight. The result of this process is a Pareto front between efficiency and weight of the machine allowing the designer to make a posteriori choice. A particular optimal machine is chosen and its performances are validated with FE analysis. This study carries out an optimal multiphysic and multiobjective design approach that allows rationalization of the design process in a realistic computation time thanks to the analytical models involved. View full abstract»

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  • Nonlinear, Optimal Control of a Wind Turbine Generator

    Page(s): 468 - 478
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (591 KB) |  | HTML iconHTML  

    In this paper, the design of a nonlinear rotor-side controller (RSC) is developed for a wind turbine generator based on nonlinear, H2 optimal control theory. The objective is to demonstrate the synthesis of a maximum power point tracking (MPPT) algorithm. In the case of a doubly fed induction generator, it is essential that the RSC and the MPPT algorithm are synthesized concurrently as the nonlinear perturbation dynamics about an operating point is either only just stable or unstable in most real generators. The algorithm is validated based on using nonlinear estimation techniques and maximizing an estimate of the actual power transferred from the turbine to the generator. The MPPT algorithm is successfully demonstrated both in the case when no disturbances were present, as it is a prerequisite for successful implementation, and in cases when significant levels of wind disturbances are present. View full abstract»

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  • Design, Analysis, and Control of DC-Excited Memory Motors

    Page(s): 479 - 489
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1756 KB) |  | HTML iconHTML  

    In this paper, a new type of memory motors, namely the dc-excited memory motor, is proposed and implemented. The concept of dc-excited memory is due to the nature that the magnetization level of permanent magnets (PMs) in the motor can be regulated by a temporary dc current pulse and be automatically memorized. Based on an outer-rotor doubly salient motor structure, the proposed dc-excited memory motor can offer effective and efficient online air-gap flux control. Hence, it possesses the advantages of mechanical robustness, high efficiency, and wide constant power operation region. Both simulation and experimentation are carried out to verify the validity of the proposed motor. View full abstract»

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  • Multiphysics Finite-Element Modeling for Vibration and Acoustic Analysis of Permanent Magnet Synchronous Machine

    Page(s): 490 - 500
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1031 KB) |  | HTML iconHTML  

    This paper aims to describe a numerical modeling process for estimating the electromagnetic noise radiated from a permanent magnet synchronous machines. The original contributions concern the inclusion of a complete evaluation of the electromagnetic forces acting on the stator teeth, a complete 3-D structural finite-element model and a point wise approximation for acoustic calculation. Structural and acoustic responses of the targeted machine have been derived and validated using experiments. Superior precision of the proposed method has been substantiated through experiments. View full abstract»

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  • Optimum Flux Distribution With Harmonic Injection for a Multiphase Induction Machine Using Genetic Algorithms

    Page(s): 501 - 512
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2162 KB) |  | HTML iconHTML  

    This paper investigates a nontriplen multiphase induction machine when fed with harmonic current injection with different sequences for an open loop optimized flux distribution that produce a quasi-square wave in the machine air gap. This maximizes iron utilization, giving more torque per ampere. The relation between the fundamental and other harmonic components can be determined for the best iron utilization using genetic algorithms where optimum flux distribution with different injected harmonic order can be obtained. This means, the target is to optimize the flux distribution during no-load to determine the optimum constants that guarantee approximate square wave air-gap flux. The paper focuses on an 11-phase machine that can be excited with harmonics up to the ninth. The technique is assessed using both winding function and finite element analysis methods. The prototype machine is fed from an 11-phase inverter. The system DSP control using genetic algorithm produces an optimum flux distribution by using winding sequence and harmonic current injection. Simulation results for the 11-phase dq model and prototype drive experimental results are presented. View full abstract»

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  • On Active/Reactive Power Modulation of DFIG-Based Wind Generation for Interarea Oscillation Damping

    Page(s): 513 - 521
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1304 KB) |  | HTML iconHTML  

    In this paper, the interactions of the torsional dynamics of the wind turbines and power modulation for oscillations in DFIG-based wind generators are investigated. One major concern of active power modulation is its interaction with wind turbine's torsional dynamics. A study case with wind turbine torsional dynamics modeled is derived from our earlier work. Both active power modulation and reactive power modulation controls are developed in this paper. The paper successfully demonstrates the presence of interaction between active power modulation and torsional dynamics and the absence of such interaction in the case of reactive power modulation. Linear system analysis and root loci approach are employed to demonstrate such interaction. Simulation results in MATLAB/Simulink further verifies the analysis. The major contribution of this paper is: 1) the demonstration of the potential disadvantage of wind generation's active power modulation; and 2) the identification of reactive power modulation in wind generation as an alternative for interarea oscillation damping. View full abstract»

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  • Transient Response of a Wind Energy Conversion System Used as Active Filter

    Page(s): 522 - 531
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1424 KB) |  | HTML iconHTML  

    This paper details the transient operation of a wind energy conversion system (WECS) used simultaneously as an active filter and power generator. This study is intended to address the system response to two types of transient phenomena: voltage dips (fast transients) and wind speed variations (slow transients). The system response to voltage dips is governed by the electrical system dynamics and control method and results in the evaluation of the WECS low-voltage ride through capability. The study of the system response to wind speed variations requires a complete mechanical model to be included. Simulation results are presented for a typical WECS, and a discussion is carried out dealing with the generalization of the present work to other configurations. View full abstract»

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  • Validation of Single- and Multiple-Machine Equivalents for Modeling Wind Power Plants

    Page(s): 532 - 541
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1507 KB) |  | HTML iconHTML  

    This paper presents an exhaustive simulation study performed to validate the adequacy of the equivalencing method promoted by the National Renewable Energy Laboratory for modeling wind power plants by single- and multiple-machine equivalents. The main simulation results are presented for a number of steady state and transient wind turbine generator operating conditions following various faults and a typical low-voltage ride through. The impact of protection systems such as the crowbar is also taken into account. The aggregation technique has shown to be adequate for load flow, stability, and electromagnetic transient studies with limitations, as presented in the paper. View full abstract»

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  • Generic Equivalent Collector System Parameters for Large Wind Power Plants

    Page(s): 542 - 549
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1068 KB) |  | HTML iconHTML  

    This paper provides a set of generic equivalent collector system (ECS) parameters for power system studies of large wind power plants (WPPs) represented by single-machine equivalents. They are intended to be used when actual collector system data are not available for calculating specific ECS parameters. The accuracy that can be expected with the generic ECS is quantified for a sample of 17 actual WPPs in the range of 50-300 MW. Generic ECS parameters have shown to provide active and reactive powers at the ECS output whose accuracies are adequate for prospective or preliminary studies. View full abstract»

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  • A Coordinated Control Method to Smooth Wind Power Fluctuations of a PMSG-Based WECS

    Page(s): 550 - 558
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1219 KB) |  | HTML iconHTML  

    This paper presents an output power smoothing method by a simple coordinated control of DC-link voltage and pitch angle of a wind energy conversion system (WECS) with a permanent magnet synchronous generator (PMSG). The WECS adopts an AC-DC-AC converter system with voltage-source converters (VSC). The DC-link voltage command is determined according to output power fluctuations of the PMSG. The output power fluctuationsin low- and high-frequency domains are smoothed by the pitch angle control of the WECS, and the DC-link voltage control, respectively. By using the proposed method, the wind turbine blade stress is mitigated as the pitch action in high-frequency domain is reduced. In addition, the DC-link capacitor size is reduced without the charge/discharge action in low-frequency domain. A chopper circuit is used in the DC-link circuit for stable operation of the WECS under-line fault. Effectiveness of the proposed method is verified by the numerical simulations. View full abstract»

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  • A Frequency-Control Approach by Photovoltaic Generator in a PV–Diesel Hybrid Power System

    Page(s): 559 - 571
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1856 KB) |  | HTML iconHTML  

    A photovoltaic (PV) system's output power fluctuates according to the weather conditions. Fluctuating PV power causes frequency deviations in the power utilities when the penetration is large. Usually, an energy storage system (ESS) is used to smooth the PV output power fluctuations and then the smoothed power is supplied to the utility. In this paper, a simple fuzzy-based frequency-control method is proposed for the PV generator in a PV-diesel hybrid system without the smoothing of PV output power fluctuations. By means of the proposed method, output power control of a PV generator considering the conditions of power utilities and the maximizing of energy capture are achieved. Here, fuzzy control is used to generate the PV output power command. This fuzzy control has average insolation, change of insolation, and frequency deviation as inputs. The proposed method is compared with a maximum power point tracking control-based method and with an ESS-based conventional control method. The numerical simulation results show that the proposed method is effective in providing frequency control and also delivers power near the maximum PV power level. View full abstract»

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  • New On-Line Rotor Ground Fault Location Method for Synchronous Machines With Static Excitation

    Page(s): 572 - 580
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1283 KB) |  | HTML iconHTML  

    This paper presents a novel on-line rotor ground fault location method for synchronous machines, which, combined with rotor ground fault protection, can detect and locate faults in the rotor. This method is suitable for synchronous machines with static excitation systems, whose excitation field winding is fed by rectifiers through an excitation transformer. The main contribution of this new technique is that it can locate the position of a ground fault in the rotor winding online, reducing the repair time. The proposed technique is based on the analysis of the ac and dc components of the excitation voltage and the voltage measured in a grounding resistance located in the neutral terminal of the excitation transformer. This technique has been validated through computer simulations and experimental laboratory tests. View full abstract»

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  • Impacts of Hysteresis and Magnetic Couplings on the Stability Domain of Ferroresonance in Asymmetric Three-Phase Three-Leg Transformers

    Page(s): 581 - 592
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2408 KB) |  | HTML iconHTML  

    This paper investigates the stability domain of ferroresonance in asymmetric three-phase three-leg transformers considering magnetic couplings and hysteresis effects of the core. A newly developed and accurate time-domain transformer model capable of simulating dynamic and transient operating conditions is implemented in this study. The model is based on electromagnetic circuit theory and considers dynamic hysteresis effects (major and minor loops) as well as core topology, asymmetry, and magnetic flux cross-coupling interactions of the core legs. Unbalanced switching with series and shunt capacitances, which is known to increase the risk of ferroresonance, is studied with the developed model. The validity of the model under ferroresonant conditions is confirmed by comparisons with extensive experimental data. The main contribution is a new analysis of (a)symmetric three-phase transformer ferroresonance behavior with an accurate core model capable of predicting ferroresonance modes. View full abstract»

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  • A Simulation Model for a Linear Variable Gap-Reluctance Drive With Resonant Load

    Page(s): 593 - 602
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1432 KB) |  | HTML iconHTML  

    A simulation model for a linear variable gap-reluctance drive with resonant load, a device widely used in automobile horns, is developed. The model, simulable with common electrical simulators, allows fast and accurate computation of: current and voltage waveforms, gap-width; and supplied, lost, and delivered power. A method to obtain model parameters is described. The model is validated comparing simulations against measurements upon real devices. The model can be used to ascertain the behavior of new devices prior to manufacturing and also to guide later device developments. View full abstract»

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  • Generator Selection and Comparative Performance in Offshore Oscillating Water Column Ocean Wave Energy Converters

    Page(s): 603 - 614
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1097 KB) |  | HTML iconHTML  

    In the field of wind energy, electrical generator solutions have converged on a small number of technologies for specific technical and economic reasons. This paper investigates whether a similar rationale exists within the field of oscillating water column, wave energy converters. The suitability or otherwise of the various generator options in the offshore marine environment is examined in detail. Each generator configuration is then modeled and the annual energy output for a typical wave climate assessed with consideration being given to the impact of speed control on the energy output. Finally, some conclusions are drawn regarding the relative suitability of the different generator options. View full abstract»

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  • Diode-Based HVdc Link for the Connection of Large Offshore Wind Farms

    Page(s): 615 - 626
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1629 KB) |  | HTML iconHTML  

    This paper includes a technical feasibility study on the use of diode-based HVdc links for the connection of large offshore wind farms based on synchronous generators. A technique for the voltage and frequency control of the offshore ac grid is presented. The proposed control technique allows the operation of the rectifier end of the HVdc link in current or voltage control mode. Fault response to onshore voltage sags of up to 80% has been shown to be comparable to that of thyristor-based rectifiers. Moreover, the complete system shows an adequate fault-ride-through operation to solid short circuits at onshore inverter terminals. PSCAD® simulations are used to prove the technical feasibility of the proposed control techniques both in steady state and during transients. 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.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Juri Jatskevich
University of British Columbia