Application Of Bi-directional Quasi-Z-Source DC-DC Converter In Automotive 48V System

With the decrease of global fossil energy and the deterioration of environment caused by automobile exhaust emissions,and to consolidate the competitiveness of automobiles in the future,European and American and other countries have adopted various measures to energy-saving and emission-reduction.Automobile 48V system has become a research hot spot at home and abroad.Many large automotive companies have carried out research and development on automobile 48V system.The automobile 48V system retains the original 12V system,which is composed of 12V network and 48V network.The two networks are connected by DC-DC converter.It can be seen that the core component of the automobile 48V system is the bi-directional DC-DC converter,because it can ensure the bidirectional transmission of energy and realize power distribution between 12V network and 48V network.Although the traditional bi-directional DC-DC converter is simple and easy to control,its low boost capacity,low efficiency and high switching voltage stress limit its application in automobile system.In order to overcome the above shortcomings of traditional bi-directional DC-DC converters,a new bi-directional quasi-Z-source DC-DC converter topology is proposed in this paper.Based on the traditional quasi-Z-source topology,the circuit has high reliability and can meet the needs of automotive 48V system,which lays a foundation for the further development of DC-DC converters.Aiming at the shortcomings of traditional bi-directional DC-DC converter,a new bi-directional quasi-Z-source DC-DC converter is proposed.Firstly,its topology is analyzed,and its working mode are studied from both positive and negative directions.Based on the basic circuit principle and the principle of volt-second balance,the formulas of boost ratio and capacitor voltage stress are derived,and compared with the traditional DC-DC converter.Secondly,using the state space averaging method,a small signal model is established to determine the time domain behavior and operation process of the system.At the same time,the parameters of the electronic devices used in the circuit,such as inductance,capacitance and IGBT,are selected,which makes full preparations for the next simulation and experimental verification.Finally,the new quasi-Z-source DC-DC converter is simulated by matlab and verified by the experimental prototype,which proves the correctness of the theory,the application of quasi-Z-source converter in automobile 48V system has achieved some research results.