Research Of Parallel Current-Sharing Technique Of Electric Vehicle Power Supply

In present times,serious environmental pollution and energy crisis make electric vehicle has gradually become the focus. electric vehicle as a environmental, non-polluting transportation tool, will have great advantages in the market, meanwhile, the charging technology for electric vehicle is also constantly and continuously improved. Electric vehicle power supply usually adopte parallel current sharing technology in order to achieve high power output.However, As the technological level and characteristics of different component, if each module parallels directly, it is difficult to achieve current sharing. Therefore, parallel system must bo introduced current sharing technology in order to balance the load current distribution. At precent, charger commonly adopte analogy control technology such as voltage droop control method, master slave control method Etc.to achieve current sharing. These technologies have the the advantages of mature technology and low price. In recent years, digital control technology has widely used in high-power converter. Digital control technology can achieve complex control strategy and has higher stability, reliability and flexibility.The thesis deeply researchs and designs the current-sharing technique based on 75kW electric vehicle power supply. This thesis composes of five sections:The first part summarizes the commonly used current-sharing control techniques include voltage droop control method, master slave control method, average current method, largest current method. The second part designs the power supply'system structure and calculates the main circuit' parameters. The third part presents a dual-closed-loop current-sharing scheme composed of analog curent inner loop and digital voltage outer loop. Also the third part detailed analyzes four parts of analog curent inner loop which includes current controller, current detecting circuit, driving circuit, PWM circuit and five parts of digital voltage outer loop which includes voltage detecting circuit, A/D sampling, voltage controller, CAN bus communication, D/A conversion. The fourth part gives the power supply'current-sharing simulation effect in different conditions of light load, full load, load changing, reference voltage changing in the MATLAB/Simulink environment. The fifth part tests the power supply'current-sharing effect at different output current. The result of experiment shows that unbalanced degree is low than 5% either in the full load or in the light load. It satisfies the current-sharing requirements and it validates the feasibility of the parallel current-sharing scheme.