Study And Design On Bi-directional LLC Resonant Converter For Pulse Charging

With the development of electric-vehicles industry, the requirements of power battery charging methods and charger are also increasing. How to charge the battery quickly, safely and efficiently has become more important.To improve the efficiency and speed of battery charger, this thesis is studied in the pulse charging methods and LLC resonant topology which is very popular in recent years. The detail research work is as follows:First, in order to increase the battery charging speed, this thesis analyses the principles of fast charging and discharging and the polarization of the battery. By the comparison and analysis about the general battery charging methods, the method for positive and negative pulse charging is proposed.Second, researching on three common circuit topologies that can achieve positive and negative pulse charging for the purpose of raising the charging efficiency, and combining the LLC resonant soft-switching characteristics, then a bidirectional full-bridge LLC resonant converter is proposed with some partial modifications for meeting the implementation requirements of positive and negative pulse charging.Third, aim at setting up the steady-state model, this thesis analyses the basic circuit networks of the bi-directional full-bridge LLC and studies the impact of gain characteristics and the efficiency of the converter with the resonant tank parameters changing. A comparative analysis between unidirectional and bidirectional full-bridge LLC has given, then proposed the method how to design a bi-directional full-bridge LLC converter, and present the control strategy how to achieve positive and negative pulse charging.Finally, Saber simulation is used to verify the effectiveness of strategies proposed in this thesis.