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  • 1.
    Asef, Pedram
    et al.
    Univ Politecn Cataluna, BarcelonaTech, Dept Elect Engn, EEBE, Barcelona 08019, Spain..
    Bargallo Perpina, Ramon
    Univ Politecn Cataluna, BarcelonaTech, Dept Elect Engn, EEBE, Barcelona 08019, Spain..
    Barzegaran, M. R.
    Lamar Univ, Renewable Energy Microgrid Lab, Beaumont, TX 77705 USA..
    Lapthorn, Andrew
    Univ Canterbury, Dept Elect & Comp Engn, Christchurch 8041, New Zealand..
    Mewes, Daniela
    KTH, School of Industrial Engineering and Management (ITM).
    Multiobjective Design Optimization Using Dual-Level Response Surface Methodology and Booth's Algorithm for Permanent Magnet Synchronous Generators2018In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 33, no 2, p. 652-659Article in journal (Refereed)
    Abstract [en]

    This paper studies a dual-level response surface methodology (DRSM) coupled with Booth's algorithm using a simulated annealing (BA-SA) method as a multiobjective technique for parametric modeling and machine design optimization for the first time. The aim of the research is for power maximization and cost of manufacture minimization resulting in a highly optimized wind generator to improve small power generation performance. The DRSM is employed to determine the best set of design parameters for power maximization in a surface-mounted permanent magnet synchronous generator with an exterior-rotor topology. Additionally, the BA-SA method is investigated to minimize material cost while keeping the volume constant. DRSM by different design functions including mixed resolution robust design, full factorial design, central composite design, and box-behnken design are applied to optimize the power performance resulting in very small errors. An analysis of the variance via multilevel RSM plots is used to check the adequacy of fit in the design region and determines the parameter settings to manufacture a high-quality wind generator. The analytical and numerical calculations have been experimentally verified and have successfully validated the theoretical and multiobjective optimization design methods presented.

  • 2.
    Divshali, Poria Hasanpor
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Söder, Lennart
    KTH, School of Electrical Engineering and Computer Science (EECS), Electric Power and Energy Systems.
    Improving PV Dynamic Hosting Capacity Using Adaptive Controller for STATCOMs2019In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 34, no 1, p. 415-425Article in journal (Refereed)
    Abstract [en]

    High penetrations of renewable energy sources (RES) in distribution grids lead to new challenges in voltage regulation. These challenges are not just limited to the steady-state voltage rise, but they are extended to rapid voltage changes due to wind speed variations and moving clouds, casting shadows on photovoltaic panels. According to EN50160 in low-voltage (LV) grids, the steady-state voltage should not exceed 1.1 pu (static characteristic), and rapid voltage changes should be kept less than 0.05 pu (dynamic characteristic). These two characteristics may limit the maximum amount of RES that can be installed in LV grids, called, respectively, the static hosting capacity (SHC) and dynamic hosting capacity (DHC). Although existing research just evaluated SHC in distribution grids, high-penetrated RES grids can be faced with such large voltage changes, which cause a smaller DHC than the SHC. This paper studies both SHC and DHC in distribution grids and proposes an adaptive controller for static synchronous compensators to regulate the steady-state and dynamic voltage while avoiding the unnecessary increase in the reactive power. The simulation results in some German distribution grids show considerable effects of the proposed adaptive controller on improving both SHC and DHC.

  • 3.
    Nategh, Shafigh
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Huang, Zhe
    Krings, Andreas
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Thermal Modeling of Directly Cooled Electric Machines Using Lumped Parameter and Limited CFD Analysis2013In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 28, no 4, p. 979-990Article in journal (Refereed)
    Abstract [en]

    This paper presents a practical approach to model thermal effects in directly cooled electric machines. The main focus is put on modeling the heat transfer in the stator winding and to the cooling system, which are the two critical parts of the studied machines from a thermal point of view. A multisegment structure is proposed that divides the stator, winding, and cooling system into a number of angular segments. Thereby, the circumferential temperature variation due to the nonuniform distribution of the coolant in the cooling channels can be predicted. Additionally, partial computational fluid dynamics (CFD) simulations are carried out to model the coolant flow in the cooling channels and also on the outer surface of the end winding bodies. The CFD simulation results are used as input to the analytical models describing the convective heat transfer to the coolant. The modeling approach is attractive due to its simplicity since CFD simulations of the complete machine are avoided. The proposed thermal model is evaluated experimentally on two directly cooled induction machines where the stator winding is impregnated using varnish and epoxy, respectively. A good correspondence between the predicted and measured temperatures under different cooling conditions and loss levels is obtained.

  • 4.
    Nategh, Shafigh
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Zhao, Shuang
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Thermal Analysis of a PMaSRM Using Partial FEA and Lumped Parameter Modeling2012In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 27, no 2, p. 477-488Article in journal (Refereed)
    Abstract [en]

    This paper presents an advanced lumped parameter (LP) thermal model for a permanent-magnet assisted synchronous reluctance machine (PMaSRM) developed for propulsion in a hybrid electric vehicle. Particular focus is put on the stator winding and a thermal model is proposed that divides the stator slot into a number of elliptical copper and impregnation layers. The model is enabled by the derivation of an approximate analytical expression for the thermal resistance of an elliptical cylinder with constant thickness. The approach is attractive due to its simplicity and the fact that it closely models the actual temperature distribution for common slot geometries. Additionally, an analysis, using results from a proposed simplified thermal finite element model representing only one slot of the stator and its corresponding end winding, is presented in which the number of layers and the proper connection between the parts of the LP thermal model representing the end winding and the active part of winding is determined. The presented thermal model is evaluated experimentally on a PMaSRM equipped with a water cooling jacket, and a good correspondence between the predicted and measured temperatures is obtained.

  • 5.
    Nilsson, Julia
    et al.
    KTH, School of Electrical Engineering (EES), Electromagnetic Engineering.
    Bertling, Lina M.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Maintenance management of wind power systems using condition monitoring systems - Life cycle cost analysis for two case studies2007In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 22, no 1, p. 223-229Article in journal (Refereed)
    Abstract [en]

    The large growth in the wind power industry in the past years. mainly focuses on a growing market and the development of large turbines and offshore farms. The high technical availability of wind turbines comes with a greater need for frequent maintenance. Current maintenance planning is not optimized, and it is possible to make maintenance more efficient. Condition monitoring systems (CMS) could resolve the growing wind power industry's need for better maintenance management and increased reliability. Such systems are commonly used in other industries. CMS could continuously monitor the performance of the wind turbine parts and could help determine specific maintenance timing. This paper presents a life cycle cost (LCC), analysis with strategies where CMS improved maintenance planning for a single wind turbine onshore and a wind farm offshore. Case studies are based on real data from Olsvenne2 at Nasudden (Gotland, Sweden) and Kentish Flats, in the U.K. The main conclusion is that CMS benefits maintenance management of wind power systems. Improvements can be especially shown for offshore wind farm maintenance planning.

  • 6.
    Petrov, Ilya
    et al.
    Department of Electrical Engineering, LUT University, Lappeenranta, Finland.
    Lindh, Pia
    Department of Electrical Engineering, LUT University, Lappeenranta, Finland.
    Niemelä, Markku
    Department of Electrical Engineering, LUT University, Lappeenranta, Finland.
    Scherman, Eero
    Saimaa University of Applied Sciences, Lappeenranta, Finland.
    Wallmark, Oskar
    KTH, School of Electrical Engineering and Computer Science (EECS), Electrical Engineering, Electric Power and Energy Systems.
    Pyrhönen, Juha
    Department of Electrical Engineering, LUT University, Lappeenranta, Finland.
    Investigation of a direct liquid cooling system ina permanent magnet synchronous machine2019In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059Article in journal (Refereed)
    Abstract [en]

    A high demand for electrification of the transportsector has resulted in a need to provide compact and reliableelectric power trains where the electric machine is a key element.The cooling system has a strong impact on the specific torqueand power capability of the machine. The selection of thecooling solution should not be based on the steady-state coolingperformance only but also on the transient characteristics owingto the typical operational load nature of the propulsion system,where the load is not continuous (as it usually is in industrialapplications), but it frequently varies in time depending on thevehicle type and the driving style. This paper investigates indetail the cooling capabilities of a direct winding liquid coolingsolution and compares it with a traditional frame liquid coolingarrangement in the transient condition. As a result of thecomparison, it was found that the location of heat removal closeto the heat source makes the temperature transient time faster,which allows to apply overload operating points more frequently.

  • 7. Ribrant, Johan
    et al.
    Bertling, Lina M. M.
    Survey of failures in wind power systems with focus on Swedish wind power plants during 1997-20052007In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 22, no 1, p. 167-173Article in journal (Refereed)
    Abstract [en]

    The wind power industry has expanded greatly during the past few years, has served a growing market, and has spawned the development of larger wind turbines. Different designs and technical advances now make it possible to erect wind turbines offshore. The fast expansion of the wind power market faces some problems. The new designs are not always fully tested, and the designed 20-year lifetime is typically never achieved before the next generation of turbines are erected. This paper presents results from an investigation of failure statistics from four sources, i.e., two separate sources from Sweden, one from Finland, and one from Germany. Statistics reveal reliability performance of the different components within the wind turbine. The gearbox is the most critical, because downtime per failure is high compared to the other components. The statistical data for larger turbines also show trends toward higher, ever-increasing failure frequency when compared to small turbines, which have a decreasing failure rate over the operational years.

  • 8.
    Shisha, Samer
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Sadarangani, Chandur
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Loss Distribution on Solid Pole Plates of Wound-Rotor Synchronous Motors Fed From Inverters Using Direct Torque Control2012In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 27, no 1, p. 63-70Article in journal (Refereed)
    Abstract [en]

    The use of VSD (variable speed drives) is becoming prominent in industry as it has the benefit of being more energy efficient than conventional process-control mechanisms (such as throttling). VSD usually rely on the use of inverters to produce the required frequency output, which contains time harmonics that eventually induce excess losses in the machine. These losses are the subject of analysis in this study. The results show that it is possible to influence the induced current magnitude (due to the space and time harmonics) through proper design modifications, as to reduce the consequent losses. The paper focuses specifically on DTC (direct torque control) VSD application on solid pole plate synchronous machines. One of the observed effects is that the time and space harmonics are distributed differently on the pole plates.

  • 9.
    Shisha, Samer
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion. Scania.
    Sadarangani, Chandur
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Nee, Hans-Peter
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    The Effect of Copper Coating on the Losses in the Solid Pole-Plates of Inverter-Fed Wound Rotor Synchronous Machines2013In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 28, no 2, p. 298-307Article in journal (Refereed)
    Abstract [en]

    The use of solid rotor and pole-plate synchronous machines has several advantages, among which is the fact that it provides a more robust rotor compared to laminated equivalents. This paper investigates the time and space harmonic losses in solid rotor synchronous machines. The work considers the use of copper coating on the pole-plates, studying the effect that this design modification has on the losses. A recommendation is given based on this study, which is considered to reduce the time harmonic losses without detrimental effects as far as the space harmonic losses are considered.

  • 10.
    Söder, Lennart
    et al.
    KTH, School of Electrical Engineering (EES), Electric Power Systems.
    Hofmann, Lutz
    Orths, Antje
    Holttinen, Hannele
    Wan, Yih-huei
    Tuohy, Aidan
    Experience from wind integration in some high penetration areas2007In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 22, no 1, p. 4-12Article in journal (Refereed)
    Abstract [en]

    The amount of wind power in the world is increasing quickly. The background for this development is improved technology, decreased costs for the units, and increased concern regarding environmental problems of competing technologies such as fossil fuels. The amount of wind power is not spread equally over the world, so in some areas, there is comparatively a high concentration. The aims of this paper are to overview some of these areas, and 3: briefly describe consequences of the increase in wind power. The aim is also to try to draw some generic conclusions, in order to get some estimation about what will happen when the amount of wind power increases for other regions where wind power penetration is expected to reach high values in future.

  • 11.
    Wallmark, Oskar
    et al.
    KTH, School of Electrical Engineering (EES), Centres, Swedish Centre of Excellence in Electric Power Engineering, EKC2.
    Kjellqvist, Peter
    Analysis of a Low-Cost Air-Gap Winding for Permanent Magnet Synchronous Motors2009In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 24, no 4, p. 841-847Article in journal (Refereed)
    Abstract [en]

    This paper presents an analysis of a concentrated air-gap winding concept intended for low-cost, high-speed applications where the reduced winding construction cost can motivate its use. Expressions for magnet flux linkage, torque, winding inductance, and unbalanced magnetic pull are derived and compared, with good agreement, to measurements and results obtained from finite-element simulations.

  • 12.
    Yao, Yanmei
    et al.
    KTH, School of Electrical Engineering (EES), Electric power and energy systems.
    Cosic, Alija
    KTH, School of Electrical Engineering (EES), Electric power and energy systems.
    Sadarangani, Chandur
    KTH, School of Electrical Engineering (EES), Electric power and energy systems.
    Power Factor Improvement and Dynamic Performance of an Induction Machine With a Novel Concept of a Converter-Fed Rotor2016In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 31, no 2, p. 769--775Article in journal (Refereed)
    Abstract [en]

    This paper investigates an induction machine with a novel concept of the rotor fed by a converter. The stator is Y-connected and directly connected to the grid, while the rotor windings are open-ended and fed by a back-to-back converter with a floating capacitor. Power factor and efficiency improvements of the induction motor are studied with different settings of phase-shift angle between the two converters. Moreover, the dynamic performance of the induction machine is explored in MATLAB/Simulink and verified experimentally on a 1.8-kW induction machine in the laboratory. The result shows good agreement between simulation and experiment. At a constant speed, variable load operation of the induction machine is obtained by setting the frequency of the rotor voltage.

  • 13.
    YAO, YANMEI
    et al.
    KTH, School of Electrical Engineering (EES), Electric power and energy systems.
    Sadarangani, Chandur
    Efficiency Improvement of a 12-Pole 17.5 kWInduction Motor Using Converter-fed Wound RotorIn: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059Article in journal (Other academic)
    Abstract [en]

    This paper investigates an induction machine usinga novel concept of a converter-fed rotor. The stator is directlyconnected to the grid while the rotor is fed by a converter with afloating capacitor over the dc-link. In earlier work this topologyhas shown to be capable of improving the power factor andefficiency of a 4-pole induction machine. This paper exploresthe possibility to improve the power factor and efficiency of asquirrel-cage 12-pole 17.5 kW induction machine by redesigningthe cage rotor to a wound rotor to enable connection of therotor windings to the converter. A standard 12-pole squirrelcageinduction machine (SCIM) with an inherent low powerfactor is studied. An analytical model to design the wound rotorinduction machine (WRIM) is then developed. The performanceof the designed WRIM using the analytical model is shown toagree with the results from the finite element (FEM) simulations,thus verifying the correctness of the model. The analyticalmodel is then further used to design different WRIMs withdifferent dimensions and rotor slot numbers. Performances ofthese designed WRIMs show good potential for power factorand efficiency improvement. Particularly, an optimum efficiencyimprovement of 6.8%, compared with the original SCIM, hasbeen achieved.

  • 14.
    Zhao, Shuang
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Damping of Torsional Drive-Train Oscillationsusing a Position Sensorless PMSynRel DriveIn: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059Article in journal (Other academic)
  • 15.
    Zhao, Shuang
    et al.
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Wallmark, Oskar
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Leksell, Mats
    KTH, School of Electrical Engineering (EES), Electrical Energy Conversion.
    Low-Speed Sensorless Control With Reduced Copper Losses for Saturated PMSynRel Machines2013In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 28, no 4, p. 841-848Article in journal (Refereed)
    Abstract [en]

    Permanent-magnet-assisted synchronous reluctance (PMSynRel) machines are generally well suited for sensorless operation at all speeds since the rotor topology possesses a magnetic saliency. However, magnetic saturation can result in a vanishing differential saliency which renders sensorless control at certain operating points difficult (or even impossible) at low speed. In this paper, an optimization procedure, based on results from finite-element (FEM)-based simulations, is proposed. As output, current reference trajectories are obtained in which copper losses are kept at minimum, while the capability for sensorless control is still maintained. The results from the FEM-based simulations are in good agreement with the corresponding experimental results. For the experimental prototype in consideration, the torque limit when operating sensorless at low speed is increased substantially from below 45% to around 95% of its rated value with only slightly increased copper losses. Additionally, the impact of position-dependent harmonics on the magnetic cross saturation (affecting the steady-state position estimation error) is found to be substantial. This highlights that this spatial variation should be taken into consideration for accurate prediction of performance during sensorless operation even if the winding of the machine is of the conventional distributed type.

  • 16. Zheng, Ping
    et al.
    Liu, Ranran
    Thelin, Peter
    Nordlund, Erik
    Sadarangani, Chandur
    KTH, School of Electrical Engineering (EES), Electrical Machines and Power Electronics.
    Research on the cooling system of a 4QT prototype machine used for HEV2008In: IEEE transactions on energy conversion, ISSN 0885-8969, E-ISSN 1558-0059, Vol. 23, no 1, p. 61-67Article in journal (Refereed)
    Abstract [en]

    A four-quadrant transducer (4QT.) is a hybrid electric vehicle (HEV) power train concept. It can enable the internal combustion engine (ICE) to operate at optimum efficiency during all driving conditions with both torque and speed control. The thermal property is a vital problem due to its special configuration. Aiming to find the hot spot and investigate the cooling system of the 4QT, the thermal field is calculated with finite-element method (FEM). The simulation is validated by the comparisons with the experiment. The influences of the forced-air cooling, water cooling, and the distribution of the cooling channels on the cooling performance are discussed, respectively. The stator air ducts; are removed, and 12 water channels evenly distributed in the housing are employed. The design principle of the cooling system is presented. The speed impacts of air flow and water flow are discussed and provide a parameter reference for choosing the forced-air cooling fan and water pump properly.

1 - 16 of 16
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