Research And Design Of An Intelligent Charger For Electric Vehicle

Electric vehicle is the car which adopts electric power as all or part of power source for its driving system. With no fuel problem and vehicle exhaust emissions, it has obvious superiority in environmental protection, clean, energy saving etc. The research of EV has become the world's hot spot. But there are few studies in energy supply system such as battery charger and there are some theoretical and technological issues remain to be tackling. Charger development can't meet the requirements of electric vehicles. This seriously restricted the development of electric cars and popularization.In addition, the current new charging station universally adopt nobody on-duty or less attendant. This requires the charger which has a higher reliability and automation degree more completed functions and higher maintenance.In this paper, aiming at the existing charger shortage, a three-stage which is based on the analysis of the charging theory and the investigation of many charging methods, charging strategy was utilized. At the first charging stage, we take a cycle when the positive pulse stops charging, negative pulse transient discharge, and then the positive pulse charging. At the second stage, we take voltage pulse charging and continue the cycle. At the third stage, we use small current to achieve balance charging. The width of polarization negative pulse is decided by the comparison of the battery voltage, the charge current, battery temperature etc, which collect by the controller, and the value set in advance. By doing this, it can adapt various periods of charging requirements. With computer technology, the fuzzy control technology, power electronic technology and "temperature compensation" coefficient etc, we design a kind of general-purpose electric car intelligent charging machine.Ground on the High-Frequency Switching Power Supply, the charger which was composed of a three-phase rectifying cell, a fast charging converter and a filter circuit was designed. And the charging control system was based on PIC16F877 microcontroller. It communicated with BMS, obtain the battery voltage, temperature and charging current, and acquisition charger output voltage, current data to analysis and process into SCM. And with the help of fuzzy-immune-adaptive PID controller, we obtain corresponding control signal, to control the IGBT and realize the intelligent charging. Meanwhile the controller monitored each part of the voltage and current of the main circuit, as well as the temperature of IGBT and high-frequency transformer to establish the fault diagnosis and treatment system to have a good protection for charger. Control technologies in fast charging is a integrated control method which is the combination of time control, temperature control and voltage control to achieve fast and green charge.