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A Double Wound Flywheel System under Standard Drive Cycles: Simulations and Experiments
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.ORCID iD: 0000-0002-4350-5194
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
2010 (English)In: International Journal of Emerging Electric Power Systems, ISSN 1553-779X, Vol. 11, no 4, Article 6.- p.Article in journal (Refereed) Published
Abstract [en]

Flywheel systems are attractive for use in electric vehicles, being able to efficiently handle the large power needed for acceleration and regenerative braking. A double wound flywheel machine, divided in two different voltage levels by the windings, acting like a rotating transformer, is studied. The flywheel stator windings have two sides: a low voltage side connected to the battery and a high voltage side connected to the wheel motor. The load variations on the high voltage side have minimal affect on the low voltage side of the system, in which the speed control of the machine is performed. In this paper the functionality of the system is investigated by means of simulations and experiments. Different standard drive cycles are applied on the high voltage side to assess the effect of load variations in the system as a whole and particularly in the speed control. The response of the speed control system is investigated with computer simulations and experimental verification. The energy storage in the flywheel allows a steady power supply from the battery via the inverter, proving the functionality of the system.

Place, publisher, year, edition, pages
2010. Vol. 11, no 4, Article 6.- p.
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
URN: urn:nbn:se:uu:diva-140340DOI: 10.2202/1553-779X.2487OAI: oai:DiVA.org:uu-140340DiVA: diva2:383451
Available from: 2011-01-05 Created: 2011-01-05 Last updated: 2015-12-08Bibliographically approved
In thesis
1. Power Control Systems in a Flywheel based All-Electric Driveline
Open this publication in new window or tab >>Power Control Systems in a Flywheel based All-Electric Driveline
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Flywheel systems are attractive in hybrid and electric vehicles due to their ability to handle power during acceleration and braking. The combination of a flywheel device with a battery source has several advantages such as high peak power capacity, high energy density and reduction in the number of charge/discharge cycles of the battery.

A flywheel based all-electric driveline is investigated in this thesis. The novelty of the system consists in the use of a double wound flywheel machine, which divides the system in two different power levels. Due to this configuration, the system becomes efficient and can handle the power developed during fast dynamical processes.

The complete driveline consists of three main components: the battery, the flywheel machine and the wheel motor. The High-Power (HP) side of the driveline connects the flywheel machine to the wheel motor, whereas the Low-Power (LP) side connects the flywheel machine to the battery. The connections of different components of the system are made electrically through power converter devices.

The present thesis focuses on the electrical converters and control strategies used in the flywheel based all-electric driveline. The control of power converters is responsible for the logic and functionality of the driveline, being a challenging step within this project.

Different power converter topologies have been investigated: a DC/DC plus a DC/AC converter on the LP side, and an AC/DC/AC converter on the HP side. The design and assembly of the power electronics and their control scheme have been successfully implemented. Different control strategies have been suggested and a complete scaled driveline has been assembled and tested based on previous simulation results.

Results have confirmed the functionality of the driveline, where smoothed output power has been obtained from the battery, whereas the flywheel handles power transients on the traction side. An average efficiency of about 87% (battery to wheels) has been obtained. The power converter systems have been shown to be efficient and robust, with control strategies able to handle the peak energy flow in the system. A regenerative braking strategy has been simulated and a wheel-to-wheel efficiency of about 80% has been estimated.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 102 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 844
Keyword
Flywheels, batteries, electric vehicles, control systems, power electronics, electric machines, efficiency.
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Science of Electricity
Identifiers
urn:nbn:se:uu:diva-157074 (URN)978-91-554-8133-9 (ISBN)
Public defence
2011-09-30, Polhemsalen, Ångström Laboratory, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2011-09-09 Created: 2011-08-15 Last updated: 2011-11-03Bibliographically approved
2. FEM Analysis Applied to Electric Machines for Electric Vehicles
Open this publication in new window or tab >>FEM Analysis Applied to Electric Machines for Electric Vehicles
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Electric vehicle technology is an interdisciplinary field in continuous development. It appears to be a margin for improvements. The Division for Electricity at Uppsala University is doing significant research in the field. The present thesis investigates electric machines for vehicular applications, both in the driveline and in the traction motor.

Section 1 presents a driveline with two galvanically isolated voltage levels. A low power side is operated at the optimum voltage of the batteries, while a high power side is operated at a higher voltage leading to higher efficiencies in the traction motor. Both sides are coupled through a flywheel that stabilizes the power transients inherent to a drive cycle.

A review of electric machine topologies for electric vehicles is presented in Section 2. The permanent magnet excited machine is the most suitable technology for an electric driveline.

Section 3 is devoted to numerical models applied to electric machines. The equivalent circuit of a motor/generator with two sets of windings is first presented. This machine couples both sides of the driveline and drives the rotor of the flywheel. The electric parameters are calculated with custom FEM models. A discussion on slotless machines concludes with a simple model to analyze the magnetic field from one static 3D simulation. The tooth ripple losses in solid salient poles are also analyzed with a novel FEM approach. A complete description of the losses in electric machines gives a proper background for further discussion on efficiency.

Section 4 presents the experimental work constructed to validate the theoretical models. The experiments include an axial flux, single wounded prototype, an axial flux, double wound prototype and a planed radial flux coreless prototype.

Section 5 focuses on traction motors for electric vehicles. A simulated prototype illustrates a design and calculation process. The loss theory and the numerical methods presented in Section 3 are applied.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Uppsaliensis, 2011. 54 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 845
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Vehicle Engineering
Identifiers
urn:nbn:se:uu:diva-157879 (URN)978-91-554-8136-0 (ISBN)
Public defence
2011-10-07, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1,, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2011-09-16 Created: 2011-08-24 Last updated: 2011-11-03Bibliographically approved
3. Flywheel in an all-electric propulsion system
Open this publication in new window or tab >>Flywheel in an all-electric propulsion system
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Energy storage is a crucial condition for both transportation purposes and for the use of electricity. Flywheels can be used as actual energy storage but also as power handling device. Their high power capacity compared to other means of storing electric energy makes them very convenient for smoothing power transients. These occur frequently in vehicles but also in the electric grid. In both these areas there is a lot to gain by reducing the power transients and irregularities.

The research conducted at Uppsala university and described in this thesis is focused on an all-electric propulsion system based on an electric flywheel with double stator windings. The flywheel is inserted in between the main energy storage (assumed to be a battery) and the traction motor in an electric vehicle. This system has been evaluated by simulations in a Matlab model, comparing two otherwise identical drivelines, one with and one without a flywheel.

The flywheel is shown to have several advantages for an all-electric propulsion system for a vehicle. The maximum power from the battery decreases more than ten times as the flywheel absorbs and supplies all the high power fluxes occuring at acceleration and braking. The battery delivers a low and almost constant power to the flywheel. The amount of batteries needed decreases whereas the battery lifetime and efficiency increases. Another benefit the flywheel configuration brings is a higher energy efficiency and hence less need for cooling.

The model has also been used to evaluate the flywheel functionality for an electric grid application. The power from renewable intermittent energy sources such as wave, wind and current power can be smoothened by the flywheel, making these energy sources more efficient and thereby competitive with a remaining high power quality in the electric grid.

Place, publisher, year, edition, pages
Uppsala: Uppsala universitet, 2011. 50 p.
Series
Licentiate Thesis, Division of Electricity, Department of Engineering Sciences, ISSN 0349-8352
Keyword
Flywheel, electric vehicle, hybrid vehicle, power management, energy storage
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-222030 (URN)
Presentation
2011-06-10, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2014-04-09 Created: 2014-04-07 Last updated: 2014-04-09Bibliographically approved

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Goncalves de Oliveira, JanaínaLundin, Johande Santiago, JuanBernhoff, Hans

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