Showing papers on "Rotor (electric) published in 2010"
TL;DR: In this article, a combined experimental and computational study into the aerodynamics and performance of a small scale vertical axis wind turbine (VAWT) was presented, where wind tunnel tests were carried out to ascertain overall performance of the turbine and two-and three-dimensional unsteady computational fluid dynamics (CFD) models were generated to help understand the aerodynamic of this performance.
631 citations
TL;DR: A review of the state of the art and present status of active aeroelastic rotor control research for wind turbines is presented in this paper, where the authors discuss the potential of load reduction using smart rotor control concepts.
491 citations
TL;DR: In this article, the recent development and new topologies of flux-switching machines, with particularly emphasis on the permanent magnet (PM) type, have been discussed, including winding configurations, combinations of stator and rotor pole numbers, rotor pole width, split ratio, etc.
Abstract: This paper overviews the recent development and new topologies of flux-switching (FS) machines, with particularly emphasis on the permanent magnet (PM) type. Specific design issues, including winding configurations, combinations of stator and rotor pole numbers, rotor pole width, split ratio, etc., are investigated, while the torque capability of selected FSPM machines is also compared.
393 citations
TL;DR: In this article, a simple analytical method is developed to compare the combinations of stator and rotor pole numbers in flux-switching permanent magnet (PM) machines in terms of back electromotive force (EMF) and electromagnetic torque.
Abstract: A simple analytical method is developed to compare the combinations of stator and rotor pole numbers in flux-switching permanent magnet (PM) machines in terms of back electromotive force (EMF) and electromagnetic torque The winding connections and winding factors of machines having all poles and alternate poles wound, and different numbers of phases, from two to six, are determined by the coil-EMF vectors Their differences from analyzing the conventional fractional-slot PM machines with concentrated nonoverlapping windings are highlighted The general conditions are established for balanced symmetrical back-EMF waveform It shows that the optimized rotor pole number should be close to the number of stator poles, whereas larger torque can be obtained by the machine with relatively higher rotor pole number The analysis is validated by finite-element analyses and experiment
367 citations
TL;DR: The method of the optimization design with multi-objectives for switched reluctance motors (SRMs) in electric vehicles (EVs) is proposed and the results show that the proposed method meets the requirements of EVs on electric motors well.
Abstract: The method of the optimization design with multi-objectives for switched reluctance motors (SRMs) in electric vehicles (EVs) is proposed in this paper. It is desired that electric motors for EVs have high torque, high efficiency, and high torque density. Thus, the developed optimization function is selected as the correct compromise between the maximum average torque, maximum average torque per copper loss, and maximum average torque per motor lamination volume, by using three weight factors and three base values. The stator and rotor pole arc angles are selected as the optimized variables. Furthermore, the authors also discuss the design requirements and some constraints on the optimization design. The results of the optimization design show that the proposed method meets the requirements of EVs on electric motors well. A prototype of the optimally designed in-wheel SRM for EVs has been manufactured. This paper provides a valuable method to implement the optimal design of SRMs for EVs.
281 citations
TL;DR: In this paper, the authors proposed a coaxial magnetic gear that offers higher torque density, lower cogging torque, and lower iron losses than its counterparts, which employs a Halbach permanent magnet array to constitute the PM poles in the inner rotor and a partial Halbach array for the outer rotor.
Abstract: This paper proposes a coaxial magnetic gear that offers higher torque density, lower cogging torque, and lower iron losses than its counterparts. The key is to newly employ a Halbach permanent-magnet (PM) array to constitute the PM poles in the inner rotor and a partial Halbach array (two segments per pole) for the outer rotor. The corresponding magnetic field distributions, torque transmission, and torque ripples are analytically discussed. Then, the corresponding performances are quantitatively assessed by using the finite-element method.
268 citations
TL;DR: In this paper, the behavior of a doubly fed induction generator under unbalanced grid voltage conditions is analyzed theoretically as a function of stator active and reactive instantaneous power exchange by the stator of the DFIG and the grid-side converter (GSC).
Abstract: In this paper, the behavior of a doubly fed induction generator (DFIG) is studied under unbalanced grid voltage conditions. It is shown that if no special control efforts are employed, the behavior of the generator is deteriorated, basically due to two reasons: electromagnetic torque oscillations and nonsinusoidal current exchange with the grid. These phenomena are first analyzed theoretically as a function of the stator active and reactive instantaneous power exchange by the stator of the DFIG and the grid-side converter (GSC). This analysis provides the main ideas for generation of the active and reactive power references for the rotor-side converter (RSC) and the GSC, controlled by means of direct power control techniques. Therefore, this paper proposes a new algorithm that generates the RSC power references, without the necessity of a sequence component extraction, in order to eliminate torque oscillations and achieve sinusoidal stator currents exchange. On the contrary, the GSC power references are provided by means of voltage and current sequence extraction. Finally, simulation and experimental results successfully validate the proposed power reference generation methods.
251 citations
TL;DR: A new family of SRMs which have higher number of rotor poles than stator poles is presented, using a newly defined pole design formula, and several novel combinations of the stator-rotor poles have been proposed.
Abstract: There is a great demand for efficient, quiet, reliable, and cost-effective motor drives for propulsion systems in hybrid and plug-in hybrid electric vehicles. Owing to a rigid structure and the absence of magnetic source on the rotor, a switched reluctance machine (SRM) is inherently robust and cost effective. In spite of these advantages, several challenges in the control of this machine remain an issue, including high levels of torque ripple, acoustic noise, and a relatively low torque density. This paper presents a new family of SRMs which have higher number of rotor poles than stator poles. Using a newly defined pole design formula, several novel combinations of the stator-rotor poles have been proposed. From the simulation and experimental analysis of a prototype 6/10 configuration, it has been observed that this machine produces higher torque per unit volume and comparable torque ripple when compared to a conventional 6/4 SRM with similar number of phases and constraints in volume. The results presented in this paper make this family of machines a strong contender for survivable high-performance applications for automotive propulsion systems. The simulation and experimental results for the prototype 6/10 configuration have been presented and compared to a conventional 6/4 design for verification.
244 citations
TL;DR: In this article, the authors identify and provide an understanding of the principal parameters that govern the downstream wake structure and its recovery to the free-stream velocity profile, and demonstrate that there are a number of interdependent variables that affect the rate of wake recovery and will have a significant impact on the spacing of marine current turbines within an array.
239 citations
28 May 2010
TL;DR: In this paper, the authors present a model design method for the flight control of an autonomous quad rotor, which is an under-actuated aircraft with fixed four pitch angle rotors.
Abstract: This paper presents the modelling of a four rotor vertical take-off and landing (VTOL) unmanned air vehicle known as the quadrotor aircraft. The paper presents a new model design method for the flight control of an autonomous quad rotor. The paper describes the controller architecture for the quadrotor as well. The dynamic model of the quad-rotor, which is an under actuated aircraft with fixed four pitch angle rotors, will be described. The Modeling of a quadrotor vehicle is not an easy task because of its complex structure. The aim is to develop a model of the vehicle as realistic as possible. The model is used to design a stable and accurate controller. This paper explains the developments of a PID (proportionalintegral-derivative) control method to obtain stability in flying the Quad-rotor flying object. The model has four input forces which are basically the thrust provided by each propeller connected to each rotor with fixed angle. Forward (backward) motion is maintained by increasing (decreasing) speed of front (rear) rotor speed while decreasing (increasing) rear (front) rotor speed simultaneously which means changing the pitch angle. Left and right motion is accomplished by changing roll angle by the same way. The front and rear motors rotate counter-clockwise while other motors rotate clockwise so that the yaw command is derived by increasing (decreasing) counter-clockwise motors speed while decreasing (increasing) clockwise motor speeds.
236 citations
TL;DR: The developments of a PID (proportional-integral-derivative) control method to obtain stability in flying the Quad-rotor flying object are explained.
Abstract: This paper presents the modeling of a four rotor vertical take-off and landing (VTOL) unmanned air vehicle known as the quad rotor aircraft. The paper presents a new model design method for the flight control of an autonomous quad rotor. The paper describes the controller architecture for the quad rotor as well. The dynamic model of the quad-rotor, which is an under actuated aircraft with fixed four pitch angle rotors was described. The Modeling of a quad rotor vehicle is not an easy task because of its complex structure. The aim is to develop a model of the vehicle as realistic as possible. The model is used to design a stable and accurate controller. This paper explains the developments of a PID (proportional-integral-derivative) control method to obtain stability in flying the Quad-rotor flying object. The model has four input forces which are basically the thrust provided by each propeller connected to each rotor with fixed angle. Forward (backward) motion is maintained by increasing (decreasing) speed of front (rear) rotor speed while decreasing (increasing) rear (front) rotor speed simultaneously which means changing the pitch angle. Left and right motion is accomplished by changing roll angle by the same way. The front and rear motors rotate counter-clockwise while other motors rotate clockwise so that the yaw command is derived by increasing (decreasing) counter-clockwise motors speed while decreasing (increasing) clockwise motor speeds.
Key words: Quadrotor, proportional-integral-derivative (PID) controller, vertical take-off and landing (VTOL), unmanned aerial vehicles (UAV), MATLAB / Simulink.
TL;DR: A new outer-rotor permanent-magnet vernier machine for direct-drive wind power generation is proposed, which can offer low-speed operation to directly capture wind power, and enable high-speed rotating field design to maximize the power density.
Abstract: This paper proposes a new outer-rotor permanent-magnet (PM) vernier machine for direct-drive wind power generation, which can offer low-speed operation to directly capture wind power, and enable high-speed rotating field design to maximize the power density. Compared with its mechanical gear counterpart, the proposed machine can eliminate the mechanical wear and tear as well as gear transmission loss, thus improving the generation reliability and efficiency. The key is to newly introduce the flux-modulation poles which can effectively modulate the high-speed rotating field of the armature windings and the low-speed rotating field of the PM outer rotor. By using the time-stepping finite-element method, the proposed machine can be accurately analyzed. Hence, its performances are quantitatively compared with other PM vernier machines, thus verifying its validity.
TL;DR: In this article, a feed-forward transient current control (FFTCC) scheme was proposed for the rotor side converter (RSC) of a DIF to enhance its low-voltage ride-through capability.
Abstract: High penetration of wind power requires reliable wind energy generation. A successful low-voltage ride-through (LVRT) scheme is a key requirement to achieve reliable and uninterrupted electrical power generation for wind turbines equipped with doubly fed induction generators (DFIGs). This paper proposes a feed-forward transient current control (FFTCC) scheme for the rotor side converter (RSC) of a DFIG to enhance its LVRT capability. This new control scheme introduces additional feed-forward transient compensations to a conventional current regulator. When three phase faults occur, these compensation terms correctly align the RSC ac-side output voltage with the transient-induced voltage, resulting in minimum transient rotor current and minimum occurrence of crowbar interruptions. With little additional computational effort, the proposed control scheme helps relieve the transient current stress on the RSC and helps maintain an uninterrupted active and reactive power supply from the wind turbines to the power grid. Simulation results are shown to demonstrate the effectiveness of the proposed FFTCC scheme in suppressing transient rotor currents.
TL;DR: In this paper, the authors proposed topologies of hybrid-excited flux-switching permanent magnet machines incorporating iron flux bridges to enhance the effectiveness of the field coil excitation, and a simple lumped parameter magnetic circuit model was developed to predict the effect of adjusting various parameters.
Abstract: Hybrid-excited machines utilize the synergies of permanent magnet (PM) and wound field machines. Flux-switching PM machines have emerged as an attractive machine type due to the fact that the excitation sources are located in the stator allowing a simple robust rotor whilst providing high torque density. This paper proposes topologies of hybrid-excited flux-switching PM machines incorporating iron flux bridges to enhance the effectiveness of the field coil excitation. A simple lumped parameter magnetic circuit model is developed to predict the effect of adjusting various parameters. Two-dimensional finite-element analysis has also been used to predict the machine performance, while a prototype machine has been built and tested to validate the predicted results.
TL;DR: In this paper, a mathematical model of the interaction between the flow field and the rotor blades was developed and validated by comparing its results with data obtained at Environmental Wind Tunnel (EWT) laboratory of the “Polytechnic University of Marche”.
TL;DR: In this paper, a direct-drive double rotor Vernier panent magnet (DR-VPM) machine is proposed and analyzed, and its steady and transient performances are analyzed using circuit-field-motion coupled time-stepping finite element method (CFM-TS-FEM).
Abstract: In this paper, a novel direct-drive double rotor Vernier panent magnet (DR-VPM) machine is proposed and analyzed. The key of the design is to incorporate two concentric rotors and the Vernier structure within one permanent magnet (PM) machine, while keeping the machine volume and slot number unchanged. The main merits of this proposed machine are its compact structure, improved torque density, reduced stator end winding length, and reduced copper loss. The operating principle of the machine is discussed and its steady and transient performances are analyzed using circuit-field-motion coupled time-stepping finite element method (CFM-TS-FEM). A dual-excitation PM Vernier (DE-VPM) machine and a single outer rotor PM Vernier (SR-VPM) machine are designed and compared with this proposed Vernier PM machine using CFM-TS-FEM. Comparison results as reported are used to confirm and validate the advantageous performance of the proposed machine.
TL;DR: Novel rotor designs of interior-permanent-magnet motors are developed in order to reduce harmonic iron losses at high rotational speeds under field-weakening control using an optimization method combined with an adaptive finite-element method.
Abstract: In this paper, we develop novel rotor designs of interior-permanent-magnet motors in order to reduce harmonic iron losses at high rotational speeds under field-weakening control. First, an optimization method, combined with an adaptive finite-element method, is applied to automatically determine the shapes of the magnets and rotor core. The optimized motor is manufactured to confirm the validity of the calculation. It is clarified that the iron loss of the optimized motor is reduced to nearly half of that of the conventional motor, without a significant decrease in maximum torque. Next, the contribution of each part of the rotor to the iron-loss reduction is analyzed by the experimental design method. Finally, several designs of the rotors are proposed from the viewpoints of manufacturing cost and performance.
TL;DR: In this paper, the authors proposed coordination of the selection of stators with odd number of slots per pole pair and IPM rotors with multiple layers of flux barriers in order to reduce torque ripple.
Abstract: This paper develops analytical principles for torque ripple reduction in interior permanent magnet (IPM) synchronous machines. The significance of slot harmonics and the benefits of stators with odd number of slots per pole pair are highlighted. Based on these valuable analytical insights, this paper proposes coordination of the selection of stators with odd number of slots per pole pair and IPM rotors with multiple layers of flux barriers in order to reduce torque ripple. The effectiveness of using stators with odd number of slots per pole pair in reducing torque ripple is validated by applying a finite-element-based Monte Carlo optimization method to four IPM machine topologies, which are combinations of two stator topologies (even or odd number of slots per pole pair) and two IPM rotor topologies (one- or two-layer). It is demonstrated that the torque ripple can be reduced to less than 5% by selecting a stator with an odd number of slots per pole pair and the IPM rotor with optimized barrier configurations, without using stator/rotor skewing or rotor pole shaping.
TL;DR: In this paper, the influence of stator and rotor pole numbers on the electromagnetic performance of three-phase flux-switching permanent magnet (FSPM) machines with all and alternate poles wound is investigated.
Abstract: The influence of stator and rotor pole numbers, viz. 6/5, 6/7, 12/10, 12/11, 12/13, and 12/14 stator/rotor poles, etc., on the electromagnetic performance of three-phase flux-switching permanent-magnet (FSPM) machines with all and alternate poles wound is investigated in this paper. It shows that the back-EMF waveform, winding inductance, unbalanced magnetic force, and torque density in an FSPM machine are all significantly affected by the stator and rotor pole numbers and winding configurations, as confirmed by both finite-element analyses and measurements.
TL;DR: In this article, a method to estimate the magnet temperature in surface permanent-magnet machines using high-frequency carrier signal injection is proposed. But the method is limited to the case of a single rotor.
Abstract: This paper proposes a method to estimate the magnet temperature in surface permanent-magnet machines using high-frequency carrier signal injection. The injection of a high-frequency signal, superimposed on the fundamental excitation, allows the estimation of the stator high-frequency impedance, which is a function of both the stator and rotor impedances. The temperature of the magnets is shown to have a significant weight on the overall stator high-frequency impedance, from which it can be estimated. The high-frequency carrier signal is injected intermittently in order to minimize potential adverse effects on the normal operation of the machine. This paper first explains the physics behind the magnet temperature dependence. Then, the principles of the method, as well as its practical implementation, are discussed. Experimental verification of the method is provided.
03 Aug 2010
TL;DR: In this paper, a compressible Reynolds-averaged Navier-Stokes solver is used to investigate the aerodynamics of a microscale coaxial-rotor configuration in hover.
Abstract: In this work, a compressible Reynolds-averaged Navier-Stokes solver is used to investigate the aerodynamics of a microscale coaxial-rotor configuration in hover, to evaluate the predictive capability of the computational approach and to characterize the unsteadiness in the aerodynamic flowfield of the microscale coaxial systems. The overall performance is well-predicted for a range of rpm and rotor spacing. As the rotor spacing increases, the top-rotor thrust increases and the bottom-rotor thrust decreases, while the total thrust remains fairly constant. The thrusts approach a constant value at very large rotor spacing. Top rotor contributes about 55 % of the total thrust at smaller rotor spacing, which increases to about 58% at the largest rotor separation. The interaction between the rotor systems is seen to generate significant impulses in the instantaneous thrust and power. Unsteadiness is mainly caused due to blade loading and wake effect. Additional high-frequency unsteadiness was also seen due to shedding near the trailing edge. The phasing of the top vortex impingement upon the bottom rotor plays a significant role in the amount of unsteadiness for the bottom rotor. Interaction of the top-rotor tip vortex and inboard sheet with the bottom rotor results in a highly three-dimensional shedding on the upper surface of the blade in the outboard region and a two-dimensional shedding on the lower surface at the inboard portion of the blade. The wake of the top rotor contracts faster compared with that of the bottom rotor because of the vortex-vortex interaction. Further, the top-rotor wake convects vertically down at a faster rate due to increased inflow.
TL;DR: In this article, a multi-objective optimal controller design of a doubly-fed induction generator (DFIG) wind turbine system using differential evolution (DE) is presented, where objective functions addressing the steady-state stability and dynamic performance at different operating conditions are implemented to optimise the controller parameters of both the rotor and grid-side converters.
Abstract: Multi-objective optimal controller design of a doubly-fed induction generator (DFIG) wind turbine system using differential evolution (DE) is presented. A detailed mathematical model of DFIG wind turbine with a closed-loop vector control system is developed. Based on this, objective functions addressing the steady-state stability and dynamic performance at different operating conditions are implemented to optimise the controller parameters of both the rotor and grid-side converters. A superior ?-constraint method and method of adaptive penalties are applied to handle the multi-objective problem and the constraint with DE, respectively. Eigenvalue analysis and time-domain simulations are performed on a single machine infinite bus system as well as a nine-bus multi-machine system with two DFIG wind turbines to illustrate the control performance of the DFIG wind turbine with the optimised controller parameters. The electric energy productions of the studied DFIG wind turbine system with and without optimised controller parameters under turbulent wind speed are also demonstrated.
TL;DR: In this article, the authors investigated the magnetic pull in ferrite-magnet fractional-slot brushless permanent magnet motors due to either magnetic asymmetry or static rotor eccentricity.
Abstract: We report on an investigation into the unbalanced magnetic pull (UMP) in ferrite-magnet fractional-slot brushless permanent-magnet motors due to either magnetic asymmetry or static rotor eccentricity. We justify the work in terms of the establishment of total indicated runout (TIR) tolerance and use 10% eccentricity as the nominal tolerance. The UMP will generate force and vibration, which causes wear. We investigated several machines with different pole numbers, slot numbers, and winding arrangements. Some of the windings contain sub-harmonics, and we found these to be more susceptible to UMP when there is rotor eccentricity and also to produce vibrating UMP. We found that consequent rotor poles produce high UMP under centered and rotor eccentricity conditions. We conducted detailed finite-element studies to calculate the UMP.
TL;DR: In this article, a curtain design has been arranged so as to improve the low performance levels of the Savonius wind rotors, and performance experiments have been carried out when the rotor is with and without curtain.
TL;DR: The shape memory alloy (SMA) technology has been used in a number of large-scale SMA-based programs, such as the SAMPSON smart inlet and variable geometry chevron as discussed by the authors.
Abstract: In order to continue the current rate of improvements in aircraft performance, aircraft and components which are continuously optimized for all flight conditions, will be needed. Toward this goal morphing-capable, adaptive structures based on shape memory alloy (SMA) technology that enable component and system-level optimization at multiple flight conditions are being developed. This paper reviews five large-scale SMA based technology programs initiated by The Boeing Company. The SAMPSON smart inlet program showed that fully integrated SMA wire bundles could provide a fighter aircraft with a variable engine inlet capability. The reconfigurable rotor blade program demonstrated the ability of highly robust, controlled 55-Nitinol tube actuators to twist a rotor blade in a spin stand test to optimize rotor aerodynamic characteristics. The variable geometry chevron (VGC) program, which was the first use of 60-Nitinol for a major aerospace application, included a flight test and static engine test of the GE90-115B engine fitted with controlled morphing chevrons that reduced noise and increased engine efficiency. The deployable rotor tab employed tube actuators to deploy and retract small fences capable of significantly reducing blade-vortex interaction generated noise on a rotorcraft. Most recently, the variable geometry fan nozzle program has built on the VGC technology to demonstrate improved jet engine performance. Continued maturation of SMA technology is needed in order to develop innovative applications and support their commercialization.
TL;DR: In this paper, a framework for analysis of harmonics in a doubly fed induction generator (DFIG) caused by nonsinusoidal conditions in rotor and unbalance in stator was developed.
Abstract: This paper develops a framework for analysis of harmonics in a doubly fed induction generator (DFIG) caused by nonsinusoidal conditions in rotor and unbalance in stator. Nonsinusoidal rotor voltages are decomposed into harmonic components and their corresponding sequences are identified. Induced harmonics in stator are analyzed and computed, from which the torques produced by these interactions between stator and rotor harmonic components can be found. During unbalanced stator conditions, symmetric component theory is applied to the stator voltage to get positive-, negative-, and zero-sequence components of stator and rotor currents. The steady-state negative-sequence equivalent circuit for a DFIG is derived based on the reference frame theory. Harmonic currents in the rotor are computed based on the sequence circuits. In both scenarios, the harmonic components of the electromagnetic torque are calculated from the interactions of the harmonic components of the stator and rotor currents. Three case studies are considered, namely: 1) nonsinusoidal rotor injection; 2) an isolated unbalanced stator load scenario; and 3) unbalanced grid-connected operation. The analysis is verified with results from numerical simulations in Matlab/Simulink. For illustration, the second case is verified using experiments. The simulation results and experimental results agree well with the results from analysis.
TL;DR: Considerations are given regarding the winding arrangements so as to avoid excessive torque ripple and unbalanced radial forces in faulty operating conditions, and various winding configurations of dual three-phase windings are taken into account.
Abstract: In order to increase the fault tolerance of a motor drive, multiphase systems are adopted. Since custom solutions are expensive, machines with dual three-phase windings supplied by two parallel converters seem to be more convenient. In the event of a fault, one of the two three-phase windings (the faulty winding) is disconnected, and the motor is operated by means of the healthy winding only. A fractional-slot permanent-magnet (PM) motor with 12 slots and 10 poles is considered with two different rotor topologies: the interior PM (IPM) rotor and the surface-mounted PM rotor. Various winding configurations of dual three-phase windings are taken into account, comparing average torque, torque ripple, mutual coupling among phases, overload capability, and short-circuit behavior. Considerations are given regarding the winding arrangements so as to avoid excessive torque ripple and unbalanced radial forces in faulty operating conditions. An IPM motor prototype has been built, and experimental results are carried out in order to verify the numerical predictions.
TL;DR: This paper is a review of various effective Hamiltonians, methods and codes dealing with asymmetric-top molecules containing one internal rotor with C 3 v symmetry, aimed at helping high-resolution spectroscopists to find the most appropriate method and code to assign and fit their internal rotor spectra.
TL;DR: In this paper, the authors investigated the low voltage ride-through (LVRT) control of wind turbines with doubly fed induction generators (DFIGs) under symmetrical voltage dips.