Author: Siu-Wo ChanPublisher: Open Dissertation Press
ISBN: 9781361471371
Category :
Languages : en
Pages :
Book Description
This dissertation, "Design, Control and Application of Battery-ultracapacitor Hybrid Systems" by Siu-wo, Chan, 陳兆和, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract Rechargeable batteries have been widely adopted for many types of equipment, including mobile phones, notebook computers and electric vehicles (EVs). The off-line operation times of those devices depend on the energy storage capacities of batteries. Strictly speaking, the power densities as well as the energy densities of batteries determine the operation times. For most portable electronics devices, power management schemes have been implemented to save energy. Usually, auxiliary parts like screens will be deactivated first and then the microprocessors of those devices will also enter sleep-mode. Energy consumption of the systems in idle stage drops below one-tenth of the nominal ratings. However, such power management schemes could not effectively enhance the operation times of certain high power rating devices like EVs. High energy density batteries like lithium-ion battery and nickel cadmium battery have been commercialized, and the storage capacities are triple that of lead-acid cells invented long time ago. Certainly, they are beneficial to the operation times of portable equipment. However, the power densities of those batteries are inadequate under certain circumstance. Bursts of current are required for the normal operations of various kinds of loads, especially with systems consisting motors. Acceleration of an EV or starting of the motor will lead to sudden increase of current consumption. It should be noted that the usable capacities of batteries depend on the magnitudes of loading current as well as the storage capacities. Even worse, the life spans of batteries will be shortened under high rates of discharging. Hybridization of batteries and ultracapacitors mitigates the problem. The main aim of this project is to study and design new circuits for the application of battery-ultracapacitor hybrid system. Ultracapacitors have just entered the commercialization stage. These new kinds of electric power storage devices possess the great advantage of high power density. Other advantages include wide temperature range, long life, and high charging and discharging efficiency. When ultracapacitors are used in combination with other energy storages and sources like batteries and fuel cells, the hybrid systems can meet the goals of performance and cost better than a single VII energy storage device. The major applications of battery-ultracapacitor hybrid systems are for transportation and automotive domain. The repetitive acceleration and braking of vehicles, buses, mass transit trains, and metro systems are ideal for this technology. Since ultracapacitors are able to absorb and deliver a burst of current, they can capture regenerative breaking energy and re-applying the energy for acceleration later on. This not only saves energy, but also extends life spans and usable capacities of batteries. The characteristics of different kinds of batteries and ultracapacitors are brought out in the first part of the thesis. Since lithium-batteries possess higher energy capacities than other batteries, their performance was studied and a low cost hardware circuit for available capacity detection was built. The characteristic of a battery-ultracapacitor hybrid system was then appraised. A dedicated charger for ultracapacitors used for battery-ultracapacitor systems was developed, which exhibits distinct advantages over common chargers. Finally, an innovative switched-capacitor multilevel
