Design of an Onboard Battery Charger for an Electric Vehicle
Total Page：16
File Type：pdf, Size：1020Kb
CODEN:LUTEDX/(TEIE-5148)/1 -66/(2001 ) Design of an Onboard Battery Charger for an Electric Vehicle Simon Heckford Department of Industrial Electrical Engineering and Automation Lund University DISCLAIMER Portions of this document may be illegible in electronic image products. Images are produced from the best available original document. .,, . ,., + I certify that all the material in this thesis which is not my own work has been identified and that no material is included for which a degree has previously been conferred upon me. Signed: .&x.... w.. .. .. Simon Heckford DESIGN OF AN ONBOARD BATTERY CHARGER FOR AN ELECTRIC VEHICLE SIMONHECKFORD 3m YEAR INDIVIDUALPROJECT 2000 Acknowledgements I would like to express my sincere thanks to Professor Mats Alakiila, my host supervisor for the project at the Department of Industrial Electrical Engineering and Automation, Lund Institute of Technology. Without his assistance, I would never have embarked upon the project, and he gave me invaluable support whilst undertaking the project. I must also express my gratitude to Per Karlsson, a Ph.D. Student at the department. Without his knowledge and continual support, undertaking the project would have been a near-impossible task since I had no previous knowledge of power electronics. He was always on hand to offer guidance and during the course of the project, it became very apparent that he has a high tolerance level!!! Other members of staff who have been of particular assistance during the project are H&an Skarrie, Bengt Simonsson, and Niklas Fridstrand,, although I must thank everyone at the department as a whole, for their constant support and goodwill. In addition, I must also thank Sabine Marksell, a student who was also working on the project and was always ready to give assistance. In Exeter, I would of course like to thank Dr Mike Hcmvood, my home supervisor. In addition, I am very grateful to Lorna Howe and Gavin Tabor, coordinators for the Erasmus scheme. Without their organization, it would not have been possible for me to obtain the added benefit of experiencing a different culture whilst carrying out my project. Contents f. Introduction ................................................................................... 1 1.1 Fast chargkg ...................................................................... 1 1.2 Impact on the @d .............................................................. 3 1.3 Selected solution ............................................................... 5 1.4 Specification ...................................................................... 6 1.5 Particular design problems ................................................ 7 1.6 Disposal of therepoti ......................................................... 7 2. Modulation and Control ............................. ...................................9 3. Design of Hardware ................................... ................................. 71 3.1 Semiconductors and DC-link capacitance ....................... 11 3.2 AC side inductance ......................................................... 11 3.2.1 Calculation of inductance using TFID ........................................ 17 3.2.2 Calculation of inductance using the IEC 1000-3-4 standard...... 19 3.3 Battery side inductance ................................................... 20 3.3.1 Calculation of inductance using fundamental component..........20 3.3.2 Calculation of inductance by summing of all components ........24 3.4 Parasitic capacitors on the DC and battery side ...............24 4. Analysis of Zero Sequence Current ..........................................27 5. Implementation of inductances .................................................32 6. Conclusions and Recommendations .........................................33 7. References ..................................................................................35 Appendices Appendixl: The Electric Sniper Appendix2: AC Propulsion tzero Appendix3: Similar products Appendix 4: A Dual Purpose Battery Charger for Electric Vehicles Appendix 5: Simulink models Appendix 6: IEC 1000-3-4 standard used for determining L& Appendix 7: Data sheet giving Fourier Series Appendix 8: Data Ilom Fourier series calculations Summary This report describes the design of an on-board battery charger for an electric sports car. There are already various battery charger units on the market. However, these are not specifically designed for this application, and consequently do not provide an ideal solution. Because these products are not specific to one application, and instead opt to cover a variety of briefs, they are not ideal. They also tend to be heavier and more expensive than if the charger was built specifically for one purpose. The main design considerations were that the charger should be compact and lightweight. It was also specified that the design should be able to operate using either the single- phase or three-phase AC supply. Before the design process for the battery charger COUIC[commence, it was necessary for the author to get an appreciation of power electronics, since he had no previous experience in the subject. The author focused his attention on areas of the subject most valuable to the project, including becoming familiar with the principle behind battery chargers. Once the required knowledge was obtained, the author could begin designing the charger. The majority of the design was actually undertaken using two soilware packages called MATLAB and Simulink, whilst also using the knowledge acquired. Regular discussions were had with the project team in order to ensure that the correct methodology was being used and a suitable design was duly developed. Possible further work was identified which could not be carried out within the time constraints of this project. 1. Introduction With the increasing concerns over environmental ismes, alternatives to the Internal Combustion Engine (ICE) are gaining greater popularity. The electrically driven vehicle is the main environmentally friendly alternative. The Industrial Electrical Engineering and Automation (IEA) department at the Lunds Tekniska Hogskola (or in English, Lund Institute of Technology and abbreviated to LTH) has been involved with a project designing and constructing an electric sports car - called the Electric Sniper - since autumn 1999. The car was originally built with a conventional engine fi-om Saab, but it was decided to make an electrically powered derivative. Information regarding the Sniper electric sports car is shown in Appendix 1. Various staff and another student from the university have been involved in the project, working on the tasks that were given to the IEA. Ths author’s role was to design the hardware for the charging unit, essentially a power converter. The concept of an electric sports car is a fairly recent initiative and, up until recently, a contradiction in terms, since the performance of electric vehicles is impaired by the weight penalty of the batteries. However, there is an electric sports car, soon to be released on the market, whose performance exceeds that of sports cars manufacturers renowned for producing performance cars, including Porsche and Ferrari. Information on this model can be found in Appendix 2. The design of the battery charger uses power electronics. This was a subject that was unfamiliar to the author at the start of the project. Power electronics can be defined as a process whereby the voltage and current are optimised to best suit a specific application, by controlling the flow of electric current. The IEEE (Institute of Electrical and Electronics Engineers) provide the following formal definition for Power Electronics by stating “This technology encompasses the use of electronic components, the application of circuit theor,y and design techniques, and the development of analytical tools toward efficient electronic conversion, control, and conditioning of electric power.” 1.1 Fast charging Charging of a battery is achieved by supplying a DC current. Through an electro- chemical process, the current provides electrical charge that is stored in the battery. Current is defined as the transport of electrical charge, per unit time. As a result, the energy delivered during the process of charging is determined by both the amount of DC 1 current supplied and the time elapsed. Electrical energy is transferred from a generator to the consumer in AC quantities. Consequently, such energy has to be converted into DC quantities. This is a primary role for the battery charger. There is one underlying problem regarding the Electric Vehicle (EV), dictating that is not yet a very practical alternative to cars fuelled by a combustion engine. Whereas, a vehicle with an Internal Combustion Engine (ICE) can be refbeled in a couple of minutes, recharging an EV inevitably takes longer. It is possible to charge an EV in approximately one or two hours. Charging by this method is called fast charging. In order to offer a realistic alternative to the ICE, fast charging is the only practical method of charging an EV. However, in order to provide 75 kW, a very large charger is required. This would mean that it could not be contained within the car, and hence it is mounted externally of the vehicle, and used at a “charger station”. Such a charger exists and is called the DUAL battery charger and two prototypes are in use in Sweden: one in Malmo and another in Stockholm. It is able to charge a bus using 375 V batteries, at a current of 2CIOA,corresponding