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A magnetization system with active compensation of unbalanced magnetic pull for synchronous machines with rotating exciters is demonstrated. The system used switched power electronics and a digital control system to control the currents in four rotor pole groups, each consisting of 3 poles. It was mounted on the shaft of a synchronous machine, providing an interface between a permanent magnet outer-pole brushless exciter and the segmented field winding. Measurements of magnetic flux density on each pole face and current control made it possible to control the airgap magnetic flux density to balance the machine magnetically, thus removing flux density space harmonics in the airgap and also the unbalanced magnetic pull. The construction of the system is presented along with results from experiments and simulations. Tests were performed with the stator winding both in series and with two parallel circuits. Approximately 80% reduction of static forces and 60% reduction of dynamic forces between the stator and rotor were observed when the system was running.
Fredrik Evestedt; J. Jose Perez-Loya; C. Johan D. Abrahamsson; Urban Lundin. Mitigation of Unbalanced Magnetic Pull in Synchronous Machines With Rotating Exciters. IEEE Transactions on Energy Conversion 2020, 36, 812 -819.
AMA StyleFredrik Evestedt, J. Jose Perez-Loya, C. Johan D. Abrahamsson, Urban Lundin. Mitigation of Unbalanced Magnetic Pull in Synchronous Machines With Rotating Exciters. IEEE Transactions on Energy Conversion. 2020; 36 (2):812-819.
Chicago/Turabian StyleFredrik Evestedt; J. Jose Perez-Loya; C. Johan D. Abrahamsson; Urban Lundin. 2020. "Mitigation of Unbalanced Magnetic Pull in Synchronous Machines With Rotating Exciters." IEEE Transactions on Energy Conversion 36, no. 2: 812-819.
In this paper, a method to control the harmonic content of the magnetic flux density in the airgap of a synchronous machine is presented. Voltage harmonics in one phase as well as the exciting magnetic forces can be affected. Switched power electronics were used to provide the field current to a synchronous machine, the control added specific current harmonics to the DC field current in order to minimize either voltage harmonics or magnetic forces. The method is verified and compared with simulations and experiments on an existing electrical machine.
Fredrik Evestedt; J. José Pérez-Loya; C. Johan D. Abrahamsson; Urban Lundin. Controlling airgap magnetic flux density harmonics in synchronous machines using field current injection. Electrical Engineering 2020, 103, 195 -203.
AMA StyleFredrik Evestedt, J. José Pérez-Loya, C. Johan D. Abrahamsson, Urban Lundin. Controlling airgap magnetic flux density harmonics in synchronous machines using field current injection. Electrical Engineering. 2020; 103 (1):195-203.
Chicago/Turabian StyleFredrik Evestedt; J. José Pérez-Loya; C. Johan D. Abrahamsson; Urban Lundin. 2020. "Controlling airgap magnetic flux density harmonics in synchronous machines using field current injection." Electrical Engineering 103, no. 1: 195-203.
The working principle of the wave energy converter (WEC) developed at Uppsala University (UU) is based on a heaving point absorber with a linear generator. The generator is placed on the seafloor and is connected via a steel wire to a buoy floating on the surface of the sea. The generator produces optimal power when the translator's oscillations are centered with respect to the stator. However, due to the tides or other changes in sea level, the translator's oscillations may shift towards the upper or lower limit of the generator's stroke length, resulting in a limited stroke and a consequent reduction in power production. A compensator has been designed and developed in order to keep the generator's translator centered, thus compensating for sea level variations. This paper presents experimental tests of the compensator in a lab environment. The wire adjustments are based on online sea level data obtained from the Swedish Meteorological and Hydrological Institute (SMHI). The objective of the study was to evaluate and optimize the control and communication system of the device. As the device will be self-powered with solar and wave energy, the paper also includes estimations of the power consumption and a control strategy to minimize the energy requirements of the whole system. The application of the device in a location with high tides, such as Wave Hub, was analyzed based on offline tidal data. The results show that the compensator can minimize the negative effects of sea level variations on the power production at the WEC. Although the wave energy concept of UU is used in this study, the developed system is also applicable to other WECs for which the line length between seabed and surface needs to be adjusted.
Mohd Nasir Ayob; Valeria Castellucci; Johan Abrahamsson; Rafael Waters. A Remotely Controlled Sea Level Compensation System for Wave Energy Converters. Energies 2019, 12, 1946 .
AMA StyleMohd Nasir Ayob, Valeria Castellucci, Johan Abrahamsson, Rafael Waters. A Remotely Controlled Sea Level Compensation System for Wave Energy Converters. Energies. 2019; 12 (10):1946.
Chicago/Turabian StyleMohd Nasir Ayob; Valeria Castellucci; Johan Abrahamsson; Rafael Waters. 2019. "A Remotely Controlled Sea Level Compensation System for Wave Energy Converters." Energies 12, no. 10: 1946.
Unbalanced magnetic pull (UMP) is typically caused by rotor or stator shape defects, electrical short circuits, eccentric rotor/stator bores as well as unreasonable pole-slot combinations. It leads to vibration and increases noise and energy losses of the machine. By actively controlling the magnetic fields and forces that arise between the rotor and stator by regulating the rotor field current of separated pole groups, it is possible to cancel it. In this contribution, we measured and calculated the currents induced in the damper bars for a synchronous machine test rig under 20% static eccentricity with and without active compensation of UMP. This was utilized to validate our finite element calculations. Afterwards, we performed loss calculations for a 74 MVA synchronous generator with and without stator parallel circuits. We found that, with active compensation of UMP for an eccentric machine, the damper bar currents and stator parallel circuit circulating currents can be eliminated and the electromagnetic efficiency of the machine which has a static eccentricity fault increases.
Jesus Jose Perez-Loya; C. Johan D. Abrahamsson; Urban Lundin; Johan Abrahamsson. Electromagnetic Losses in Synchronous Machines During Active Compensation of Unbalanced Magnetic Pull. IEEE Transactions on Industrial Electronics 2018, 66, 124 -131.
AMA StyleJesus Jose Perez-Loya, C. Johan D. Abrahamsson, Urban Lundin, Johan Abrahamsson. Electromagnetic Losses in Synchronous Machines During Active Compensation of Unbalanced Magnetic Pull. IEEE Transactions on Industrial Electronics. 2018; 66 (1):124-131.
Chicago/Turabian StyleJesus Jose Perez-Loya; C. Johan D. Abrahamsson; Urban Lundin; Johan Abrahamsson. 2018. "Electromagnetic Losses in Synchronous Machines During Active Compensation of Unbalanced Magnetic Pull." IEEE Transactions on Industrial Electronics 66, no. 1: 124-131.
This paper presents two wave energy concepts for small-scale electricity generation. In the presented case, these concepts are installed on the buoy of a heaving, point-absorbing wave energy converter (WEC) for large scale electricity production. In the studied WEC, developed by Uppsala University, small-scale electricity generation in the buoy is needed to power a tidal compensating system designed to increase the performance of the WEC in areas with high tides. The two considered and modeled concepts are an oscillating water column (OWC) and a heaving point absorber. The results indicate that the OWC is too small for the task and does not produce enough energy. On the other hand, the results show that a hybrid system composed of a small heaving point absorber combined with a solar energy system would be able to provide a requested minimum power of around 37.7 W on average year around. The WEC and solar panel complement each other, as the WEC produces enough energy by itself during wintertime (but not in the summer), while the solar panel produces enough energy in the summer (but not in the winter).
Mohd Nasir Ayob; Valeria Castellucci; Malin Göteman; Joakim Widen; Johan Abrahamsson; Jens Engstrom; Rafael Waters. Small-Scale Renewable Energy Converters for Battery Charging. Journal of Marine Science and Engineering 2018, 6, 26 .
AMA StyleMohd Nasir Ayob, Valeria Castellucci, Malin Göteman, Joakim Widen, Johan Abrahamsson, Jens Engstrom, Rafael Waters. Small-Scale Renewable Energy Converters for Battery Charging. Journal of Marine Science and Engineering. 2018; 6 (1):26.
Chicago/Turabian StyleMohd Nasir Ayob; Valeria Castellucci; Malin Göteman; Joakim Widen; Johan Abrahamsson; Jens Engstrom; Rafael Waters. 2018. "Small-Scale Renewable Energy Converters for Battery Charging." Journal of Marine Science and Engineering 6, no. 1: 26.
Flywheel Energy Storage Systems (FESS) are a good alternative for power handling and energy storage in hybrid and electric vehicles. The combination of a FESS and a battery has several advantages, such as higher peak power capacity and reduced number of charging/discharging cycles in the battery. Nevertheless, batteries have a significant effect on the performance of the system and the control of the flywheel-battery link should be optimized in order to increase the system efficiency.
Janaína Gonçalves De Oliveira; Johan Abrahamsson; Hans Bernhoff. Battery Discharging Power Control in a Double-Wound Flywheel System Applied to Electric Vehicles. ENERGYO 2018, 1 .
AMA StyleJanaína Gonçalves De Oliveira, Johan Abrahamsson, Hans Bernhoff. Battery Discharging Power Control in a Double-Wound Flywheel System Applied to Electric Vehicles. ENERGYO. 2018; ():1.
Chicago/Turabian StyleJanaína Gonçalves De Oliveira; Johan Abrahamsson; Hans Bernhoff. 2018. "Battery Discharging Power Control in a Double-Wound Flywheel System Applied to Electric Vehicles." ENERGYO , no. : 1.
Synchronous motors are reliable and efficient, but it is relatively difficult to start them. In some cases, a variable frequency drive is utilized. In some other, asynchronous start is achieved by virtue of induced currents in a solid rotor, or a rotor damper cage installed for this purpose. In this contribution, a method to start a synchronous machine without a damper cage is presented. The starting was achieved by inverting the polarity of the rotor field winding in a timely manner with respect to the rotating stator field. The technique was verified with experiments performed on a 200 kVA experimental test rig and also simulated on a 20 MVA machine.
J. J. Perez-Loya; C. J. D. Abrahamsson; Fredrik Evestedt; Urban Lundin. Demonstration of Synchronous Motor Start by Rotor Polarity Inversion. IEEE Transactions on Industrial Electronics 2017, 65, 8271 -8273.
AMA StyleJ. J. Perez-Loya, C. J. D. Abrahamsson, Fredrik Evestedt, Urban Lundin. Demonstration of Synchronous Motor Start by Rotor Polarity Inversion. IEEE Transactions on Industrial Electronics. 2017; 65 (10):8271-8273.
Chicago/Turabian StyleJ. J. Perez-Loya; C. J. D. Abrahamsson; Fredrik Evestedt; Urban Lundin. 2017. "Demonstration of Synchronous Motor Start by Rotor Polarity Inversion." IEEE Transactions on Industrial Electronics 65, no. 10: 8271-8273.
The static exciter is dominating among large grid-connected generators due to the weak dynamic performance of conventional brushless exciters. In this paper, a six-phase outer pole permanent magnet rotating brushless exciter is evaluated with different active rectification topologies. Both thyristor-based and chopper-based topologies are considered. A fast-response brushless excitation system is obtained by replacing the conventional rotating diode bridge rectifier with the proposed active rectification topologies on the shaft. The given two-stage system generates its own excitation power directly from the shaft, contrary to static exciters. The selection of an appropriate rectification topology could minimize the rotor armature phase currents for a given generator field current. The objective is a high power factor and a high utilization of the exciter machine. An optimal rectification topology makes higher ceiling currents possible, improving the transient behavior of the synchronous generator. In this paper we show that six-phase topologies add complexity, but improve exciter redundancy, increase the available ceiling voltage and reduce the steady state torque ripple. Experimental results are given for validating the models implemented for the analysis.
Jonas Kristiansen Noland; Fredrik Evestedt; J. Jose Perez-Loya; Johan Abrahamsson; Urban Lundin. Testing of Active Rectification Topologies on a Six-Phase Rotating Brushless Outer Pole PM Exciter. IEEE Transactions on Energy Conversion 2017, 33, 59 -67.
AMA StyleJonas Kristiansen Noland, Fredrik Evestedt, J. Jose Perez-Loya, Johan Abrahamsson, Urban Lundin. Testing of Active Rectification Topologies on a Six-Phase Rotating Brushless Outer Pole PM Exciter. IEEE Transactions on Energy Conversion. 2017; 33 (1):59-67.
Chicago/Turabian StyleJonas Kristiansen Noland; Fredrik Evestedt; J. Jose Perez-Loya; Johan Abrahamsson; Urban Lundin. 2017. "Testing of Active Rectification Topologies on a Six-Phase Rotating Brushless Outer Pole PM Exciter." IEEE Transactions on Energy Conversion 33, no. 1: 59-67.
Magnus Hedlund; Johan Abrahamsson; Jesús José Pérez-Loya; Johan Lundin; Hans Bernhoff. Eddy currents in a passive magnetic axial thrust bearing for a flywheel energy storage system. International Journal of Applied Electromagnetics and Mechanics 2017, 54, 389 -404.
AMA StyleMagnus Hedlund, Johan Abrahamsson, Jesús José Pérez-Loya, Johan Lundin, Hans Bernhoff. Eddy currents in a passive magnetic axial thrust bearing for a flywheel energy storage system. International Journal of Applied Electromagnetics and Mechanics. 2017; 54 (3):389-404.
Chicago/Turabian StyleMagnus Hedlund; Johan Abrahamsson; Jesús José Pérez-Loya; Johan Lundin; Hans Bernhoff. 2017. "Eddy currents in a passive magnetic axial thrust bearing for a flywheel energy storage system." International Journal of Applied Electromagnetics and Mechanics 54, no. 3: 389-404.
A hollow cylinder flywheel rotor with a novel outer rotor switched reluctance machine (SRM) mounted on the interior rim is presented, with measurements, numerical analysis and analytical models. Practical experiences from the construction process are also discussed. The flywheel rotor does not have a shaft and spokes and is predicted to store 181 Wh/kg at ultimate tensile strength (UTS) according to simulations. The novel SRM is an axial flux machine, chosen due to its robustness and tolerance for high strain. The computed maximum tip speed of the motor at UTS is 1050 m/s. A small-scale proof-of-concept electric machine prototype has been constructed, and the machine inductance has been estimated from measurements of voltage and current and compared against results from analytical models and finite element analysis (FEA). The prototype measurements were used to simulate operation during maximal speed for a comparison towards other high-speed electric machines, in terms of tip speed and power. The mechanical design of the flywheel was performed with an analytical formulation assuming planar stress in concentric shells of orthotropic (unidirectionally circumferentially wound) carbon composites. The analytical approach was verified with 3D FEA in terms of stress and strain.
Magnus Hedlund; Tobias Kamf; Juan De Santiago; Johan Abrahamsson; Hans Bernhoff. Reluctance Machine for a Hollow Cylinder Flywheel. Energies 2017, 10, 316 .
AMA StyleMagnus Hedlund, Tobias Kamf, Juan De Santiago, Johan Abrahamsson, Hans Bernhoff. Reluctance Machine for a Hollow Cylinder Flywheel. Energies. 2017; 10 (3):316.
Chicago/Turabian StyleMagnus Hedlund; Tobias Kamf; Juan De Santiago; Johan Abrahamsson; Hans Bernhoff. 2017. "Reluctance Machine for a Hollow Cylinder Flywheel." Energies 10, no. 3: 316.
Generally, PM machines are used as PMG pre-exciters in 3-stage brushless excitations systems. This paper presents the design, characterization, and prototyping of a rotating brushless PM exciter used in a proposed 2-stage excitation system for a synchronous generator. The proposed design reduces the number of components compared with conventional systems. A comparison with the state-of-the-art conventional excitation systems is given. The design of a fast-response, or high initial response, brushless exciter requires active rectification on the rotating frame, replacing the noncontrollable diode bridge. The objective was to construct an exciter with the capability of a 50 A output field current, as well as a high value of the available ceiling voltage and ceiling current. The final exciter was constructed to be fitted into an in-house synchronous generator test setup. A finite element model of the exciter was validated with experimental measurements. The exciter prototype is also compared with an alternative armature design with nonoverlapping single-layer concentrated windings, but with the same main dimensions. The paper includes a general design procedure suitable for optimization of PM brushless exciters that fulfill the requirements of their synchronous generators and the grid.
Jonas Kristiansen Noland; Fredrik Evestedt; J. Jose Perez-Loya; Johan Abrahamsson; Urban Lundin. Design and Characterization of a Rotating Brushless Outer Pole PM Exciter for a Synchronous Generator. IEEE Transactions on Industry Applications 2017, 53, 2016 -2027.
AMA StyleJonas Kristiansen Noland, Fredrik Evestedt, J. Jose Perez-Loya, Johan Abrahamsson, Urban Lundin. Design and Characterization of a Rotating Brushless Outer Pole PM Exciter for a Synchronous Generator. IEEE Transactions on Industry Applications. 2017; 53 (3):2016-2027.
Chicago/Turabian StyleJonas Kristiansen Noland; Fredrik Evestedt; J. Jose Perez-Loya; Johan Abrahamsson; Urban Lundin. 2017. "Design and Characterization of a Rotating Brushless Outer Pole PM Exciter for a Synchronous Generator." IEEE Transactions on Industry Applications 53, no. 3: 2016-2027.
This paper investigates the performance of different power electronic interfaces for a rotating brushless permanent magnet exciter, designed for a synchronous generator test setup. A passive rotating diode bridge is commonly used as the rotating interface on conventional brushless excitation systems. Those systems are known to be slow dynamically, since they cannot control the generator field voltage directly. Including active switching components on the rotating shaft, like thyristors or transistors, brushless excitation systems can be comparable to static excitation systems. Brushless excitation systems has the benefit of less regular maintenance. With permanent magnets on the stator of the designed exciter, the excitation system improves its field forcing capability. Results show that modern power electronic interfaces utilize the exciter machine optimally, increase the power factor, reduce the torque pulsations, maintain the available field winding ceiling voltage and improve the field winding controllability.
Jonas Kristiansen Noland; Fredrik Evestedt; J. Jose Perez-Loya; Johan Abrahamsson; Urban Lundin. Evaluation of different power electronic interfaces for control of a rotating brushless PM exciter. IECON 2016 - 42nd Annual Conference of the IEEE Industrial Electronics Society 2016, 1924 -1929.
AMA StyleJonas Kristiansen Noland, Fredrik Evestedt, J. Jose Perez-Loya, Johan Abrahamsson, Urban Lundin. Evaluation of different power electronic interfaces for control of a rotating brushless PM exciter. IECON 2016 - 42nd Annual Conference of the IEEE Industrial Electronics Society. 2016; ():1924-1929.
Chicago/Turabian StyleJonas Kristiansen Noland; Fredrik Evestedt; J. Jose Perez-Loya; Johan Abrahamsson; Urban Lundin. 2016. "Evaluation of different power electronic interfaces for control of a rotating brushless PM exciter." IECON 2016 - 42nd Annual Conference of the IEEE Industrial Electronics Society , no. : 1924-1929.
This paper deals with the characterization and construction of a rotating brushless PM exciter intended for synchronous generator excitation purposes. Traditionally, PM exciters are used as pre-exciters in synchronous generator excitations systems. In order to reduce the number of components and to increase the step time response of the system, a PM exciter is designed as an outer pole PM machine, with permanent magnets on the stator and armature windings on the rotor. The exciter was constructed electrically and mechanically to be fitted into an in-house synchronous generator test setup. A finite element model of the exciter was validated with no-load measurements of voltages and magnetic flux densities. The exciter was then characterized with unsaturated and saturated parameters.
Jonas Kristiansen Noland; Fredrik Evestedt; J. Jose Perez-Loya; Johan Abrahamsson; Urban Lundin. Design and characterization of a rotating brushless PM exciter for a synchronous generator test setup. 2016 XXII International Conference on Electrical Machines (ICEM) 2016, 259 -265.
AMA StyleJonas Kristiansen Noland, Fredrik Evestedt, J. Jose Perez-Loya, Johan Abrahamsson, Urban Lundin. Design and characterization of a rotating brushless PM exciter for a synchronous generator test setup. 2016 XXII International Conference on Electrical Machines (ICEM). 2016; ():259-265.
Chicago/Turabian StyleJonas Kristiansen Noland; Fredrik Evestedt; J. Jose Perez-Loya; Johan Abrahamsson; Urban Lundin. 2016. "Design and characterization of a rotating brushless PM exciter for a synchronous generator test setup." 2016 XXII International Conference on Electrical Machines (ICEM) , no. : 259-265.
A low-cost method, which integrates distance sensing functionality into a switched electromagnet by using a hybrid switching mode and current ripple measurements, is proposed. The electromagnet is controlled by a micro-controller via a MOSFET H bridge, utilizing a comparator-based current control. Additionally, a method for calculating the inductance of the electromagnet and approximating the magnetic contact between the electromagnet and its target is also presented. The resulting tool is attached to an industrial robot, and the system performance using this setup is evaluated. Distance sensing in the range of 0 mm to 5.2 mm is demonstrated. It is also shown that the relation between magnetic contact, coil current and calculated inductance can be reduced to a predictive look-up table, enabling the quality of the magnetic contact to be estimated using minimal computational effort.
Tobias Kamf; Johan Abrahamsson. Self-Sensing Electromagnets for Robotic Tooling Systems: Combining Sensor and Actuator. Machines 2016, 4, 16 .
AMA StyleTobias Kamf, Johan Abrahamsson. Self-Sensing Electromagnets for Robotic Tooling Systems: Combining Sensor and Actuator. Machines. 2016; 4 (3):16.
Chicago/Turabian StyleTobias Kamf; Johan Abrahamsson. 2016. "Self-Sensing Electromagnets for Robotic Tooling Systems: Combining Sensor and Actuator." Machines 4, no. 3: 16.
A review of flywheel energy storage technology was made, with a special focus on the progress in automotive applications. We found that there are at least 26 university research groups and 27 companies contributing to flywheel technology development. Flywheels are seen to excel in high-power applications, placing them closer in functionality to supercapacitors than to batteries. Examples of flywheels optimized for vehicular applications were found with a specific power of 5.5 kW/kg and a specific energy of 3.5 Wh/kg. Another flywheel system had 3.15 kW/kg and 6.4 Wh/kg, which can be compared to a state-of-the-art supercapacitor vehicular system with 1.7 kW/kg and 2.3 Wh/kg, respectively. Flywheel energy storage is reaching maturity, with 500 flywheel power buffer systems being deployed for London buses (resulting in fuel savings of over 20%), 400 flywheels in operation for grid frequency regulation and many hundreds more installed for uninterruptible power supply (UPS) applications. The industry estimates the mass-production cost of a specific consumer-car flywheel system to be 2000 USD. For regular cars, this system has been shown to save 35% fuel in the U.S. Federal Test Procedure (FTP) drive cycle.
Magnus Hedlund; Johan Lundin; Juan De Santiago; Johan Abrahamsson; Hans Bernhoff. Flywheel Energy Storage for Automotive Applications. Energies 2015, 8, 10636 -10663.
AMA StyleMagnus Hedlund, Johan Lundin, Juan De Santiago, Johan Abrahamsson, Hans Bernhoff. Flywheel Energy Storage for Automotive Applications. Energies. 2015; 8 (10):10636-10663.
Chicago/Turabian StyleMagnus Hedlund; Johan Lundin; Juan De Santiago; Johan Abrahamsson; Hans Bernhoff. 2015. "Flywheel Energy Storage for Automotive Applications." Energies 8, no. 10: 10636-10663.
The power production of the linear generator wave energy converter developed at Uppsala University is affected by variations of mean sea level. The reason is that these variations change the distance between the point absorber located on the surface and the linear generator located on the seabed. This shifts the average position of the translator with respect to the center of the stator, thereby reducing the generator output power. A device mounted on the point absorber that compensates for tides of small range by regulating the length of the connection line between the buoy at the surface and the linear generator has been constructed and tested. This paper describes the electro-mechanical, measurement, communication and control systems installed on the buoy and shows the results obtained before its connection to the generator. The adjustment of the line was achieved through a linear actuator, which shortens the line during low tides and vice versa. The motor that drives the mechanical device was activated remotely via SMS. The measurement system that was mounted on the buoy consisted of current and voltage sensors, accelerometers, strain gauges and inductive and laser sensors. The data collected were transferred via Internet to a Dropbox server. As described within the paper, after the calibration of the sensors, the buoy was assembled and tested in the waters of Lysekil harbor, a few kilometers from the Uppsala University research site. Moreover, the performance of the sensors, the motion of the mechanical device, the power consumption, the current control strategy and the communication system are discussed.
Valeria Castellucci; Johan Abrahamsson; Tobias Kamf; Rafael Waters. Nearshore Tests of the Tidal Compensation System for Point-Absorbing Wave Energy Converters. Energies 2015, 8, 3272 -3291.
AMA StyleValeria Castellucci, Johan Abrahamsson, Tobias Kamf, Rafael Waters. Nearshore Tests of the Tidal Compensation System for Point-Absorbing Wave Energy Converters. Energies. 2015; 8 (4):3272-3291.
Chicago/Turabian StyleValeria Castellucci; Johan Abrahamsson; Tobias Kamf; Rafael Waters. 2015. "Nearshore Tests of the Tidal Compensation System for Point-Absorbing Wave Energy Converters." Energies 8, no. 4: 3272-3291.
Valeria Castellucci; Johan Abrahamsson; Olle Svensson; Rafael Waters. Algorithm for the calculation of the translator position in permanent magnet linear generators. Journal of Renewable and Sustainable Energy 2014, 6, 063102 .
AMA StyleValeria Castellucci, Johan Abrahamsson, Olle Svensson, Rafael Waters. Algorithm for the calculation of the translator position in permanent magnet linear generators. Journal of Renewable and Sustainable Energy. 2014; 6 (6):063102.
Chicago/Turabian StyleValeria Castellucci; Johan Abrahamsson; Olle Svensson; Rafael Waters. 2014. "Algorithm for the calculation of the translator position in permanent magnet linear generators." Journal of Renewable and Sustainable Energy 6, no. 6: 063102.
This paper presents the design and optimization of a high-speed (30 000 r/min) kinetic energy storage system. The purpose of the device is to function as an energy buffer storing up to 867 Wh, primarily for utility vehicles in urban traffic. The rotor comprises a solid composite shell of carbon and glass fibers in an epoxy matrix, constructed in one curing. The shell is optimized using a combined analytical and numerical approach. The radial stress in the shell is kept compressive by integrating the electric machine, thereby avoiding delamination. Radial centering is achieved through eight active electromagnetic actuators. The actuator geometry is optimized using a direct coupling between SolidWorks, Comsol, and Matlab for maximum force over resistive loss for a given current density. The optimization results in a system with 300% higher current stiffness than the reference geometry with constant flux area, at the expense of 33% higher power loss. The actuators are driven by semipassive H bridges and controlled by an FPGA. Current control at 20 kHz with a noise of less than 5 mA (95% CI) is achieved, allowing position control at 4 kHz to be implemented.
Johan Abrahamsson; Magnus Hedlund; Tobias Kamf; Hans Bernhoff. High-Speed Kinetic Energy Buffer: Optimization of Composite Shell and Magnetic Bearings. IEEE Transactions on Industrial Electronics 2013, 61, 3012 -3021.
AMA StyleJohan Abrahamsson, Magnus Hedlund, Tobias Kamf, Hans Bernhoff. High-Speed Kinetic Energy Buffer: Optimization of Composite Shell and Magnetic Bearings. IEEE Transactions on Industrial Electronics. 2013; 61 (6):3012-3021.
Chicago/Turabian StyleJohan Abrahamsson; Magnus Hedlund; Tobias Kamf; Hans Bernhoff. 2013. "High-Speed Kinetic Energy Buffer: Optimization of Composite Shell and Magnetic Bearings." IEEE Transactions on Industrial Electronics 61, no. 6: 3012-3021.
This paper presents experimental results on an innovative electric driveline employing a kinetic energy storage device as energy buffer. A conceptual division of losses in the system was created, separating the complete system into three parts according to their function. This conceptualization of the system yielded a meaningful definition of the concept of efficiency. Additionally, a thorough theoretical framework for the prediction of losses associated with energy storage and transfer in the system was developed. A large number of spin-down tests at varying pressure levels were performed. A separation of the measured data into the different physical processes responsible for power loss was achieved from the corresponding dependence on rotational velocity. This comparison yielded an estimate of the perpendicular resistivity of the stranded copper conductor of 2.5 × 10−8 ± 3.5 × 10−9. Further, power and energy were measured system-wide during operation, and an analysis of the losses was performed. The analytical solution was able to reproduce the measured distribution of losses in the system to an accuracy of 4.7% (95% CI). It was found that the losses attributed to the function of kinetic energy storage in the system amounted to between 45% and 65%, depending on usage.
Johan Abrahamsson; Janaína Gonçalves De Oliveira; Juan De Santiago; Johan Lundin; Hans Bernhoff. On the Efficiency of a Two-Power-Level Flywheel-Based All-Electric Driveline. Energies 2012, 5, 2794 -2817.
AMA StyleJohan Abrahamsson, Janaína Gonçalves De Oliveira, Juan De Santiago, Johan Lundin, Hans Bernhoff. On the Efficiency of a Two-Power-Level Flywheel-Based All-Electric Driveline. Energies. 2012; 5 (8):2794-2817.
Chicago/Turabian StyleJohan Abrahamsson; Janaína Gonçalves De Oliveira; Juan De Santiago; Johan Lundin; Hans Bernhoff. 2012. "On the Efficiency of a Two-Power-Level Flywheel-Based All-Electric Driveline." Energies 5, no. 8: 2794-2817.
Flywheel Energy Storage Systems (FESS) are a good alternative for power handling and energy storage in hybrid and electric vehicles. The combination of a FESS and a battery has several advantages, such as higher peak power capacity and reduced number of charging/discharging cycles in the battery. Nevertheless, batteries have a significant effect on the performance of the system and the control of the flywheel-battery link should be optimized in order to increase the system efficiency.The FESS investigated in this paper has its novelty in the use of a double wound flywheel machine which divides the system in two different voltage/power levels. High-Voltage/Power (HV) side connects the flywheel machine to the wheel motor and Low-Voltage/Power (LV) side connects the flywheel machine to the battery.The present paper focuses on the converter system and the control logic which regulates battery discharging process and the flywheel rotational speed. Emphasis has been given to the overall power/energy management of the system. Simulations and experimental results show that an ON/OFF battery control allows a highly efficient system, requiring a robust speed control and high energy density for the flywheel machine.
Janaína Goncalves De Oliveira; Johan Abrahamsson; Hans Bernhoff. Battery Discharging Power Control in a Double-Wound Flywheel System Applied to Electric Vehicles. International Journal of Emerging Electric Power Systems 2011, 12, 1 .
AMA StyleJanaína Goncalves De Oliveira, Johan Abrahamsson, Hans Bernhoff. Battery Discharging Power Control in a Double-Wound Flywheel System Applied to Electric Vehicles. International Journal of Emerging Electric Power Systems. 2011; 12 (1):1.
Chicago/Turabian StyleJanaína Goncalves De Oliveira; Johan Abrahamsson; Hans Bernhoff. 2011. "Battery Discharging Power Control in a Double-Wound Flywheel System Applied to Electric Vehicles." International Journal of Emerging Electric Power Systems 12, no. 1: 1.