Design Of Active Bidirectional DC-DC Battery Equalizer

Environmental pollution and energy crisis has gradually become the two major problems in the 21 st century.With the improvement of people's awareness of environmental protection and the government's strong support,for its energy saving and environmental protection characteristics,electric vehicles will lead the future direction of the development of the automotive industry.The battery,as the core of the electric car,the development of the status quo determines the possibility of further development of electric vehicles.Due to technical limitations,the power battery of an electric vehicle is a battery pack made up of multiple single cells in series.Due to the inconsistency of the individual performance of the battery and the severe overcharge and over discharge of the battery during use,t the battery life is greatly affect,therefore,battery balancing technology for the industrialization of electric vehicles is essential.The use of battery equalization technology to the charging pile,to ensure the safety of the battery pack e and effectiveness of charging is the way to solve the problem of battery life damage.The domestic and foreign research shows that non-dissipative equalization technology is a hot subject.On the circuit structure and control method,there are many options for equalization techniques.However,many equalization methods only stay in the theoretical research,and did not fully consider the battery under the actual working environment of the parameter changes,in addition,the proposed part of the equilibrium control strategy is too complex and difficult to apply to the actual.In this paper,based on the deep analysis of the domestic and foreign research on the power cell balance technology,the design method of the active bidirectional DC-DC battery equalizer is put forward under the condition of incomplete charging and overcharging when the electric vehicle is charged.The method can realize the full charge of the lithium battery pack,which can charge the battery pack of 24 lithium batteries.The design of the battery equalization system consists of balanced main circuit and equalization controller.Firstly,the circuit design of equalizing main circuit and controller is described in detail.The circuit design method of power supply circuit,power monitoring circuit,DSP peripheral circuit,SPI module and CAN module are discussed in order to design the product grade battery equalizer.Which balance controller to DSP as the control core,supplemented by Linear Technology's LTC6804-2 voltage acquisition module;Secondly,the design of a set of battery voltage from the battery to monitor the individual voltage balance of a complete program,The effective equalization strategy and the SOC estimation algorithm are designed.Then,the simulation model of the battery equalization system is established,and the equilibrium scheme is simulated and verified.Finally,the prototype of the battery equalizer was developed,and the electromagnetic compatibility and high and low temperature tests were carried out to verify the effectiveness and reliability of the whole system design.