Control Algorithm Research And System Implementation For A New Intelligent Charger Used By Electrical Drive Vehicle

With the problems that world environment pollution and energy shortage havingbecome increasingly prominent, the travel concept of green-energy-saving and lowcarbon is being deeply rooted in the hearts. The environment friendly electrical drivevehicle has become a hot orientation of modern vehicles’ research, exploit and usage.Lead-acid batteries with the advantages of low cost,convenient to use,are widely usedin all kinds of electric drive fields. Charging technology is one of the key factors ininfluencing lead-acid battery life and performance during the using process oflead-acid batteries. Therefore in this thesis, the charging process and intelligent chargerdesign of the lead-acid batteries used by electrical drive vehicle were studyed andanalyzed in detail as followed:Firstly, the characteristics and charging process of the lead-acid batteries used byelectrical drive vehicle were analyzed, after the comparison and analysis with all kindsof charging control methods and strategies, based on multistage charging controlmethod,the control thought that lead-acid batteries could accept the joint control ofcurrent and voltage was adopted, then a four phases charging control strategy that hadthe constant current-change current pulse-constant voltage-float charging was designed.And on this basis, judging criterion and corresponding charging process’s control flowof China CHILWEE group48V20AH lead-acid battery’s each charging status weregiven in this paper.Secondly, the charger’s size, typical structure and output control algorithms of thelead-acid batteries used by electrical drive vehicle were analyzed and discussed in thisthesis. According to the actual needs of the market, a new intelligent charger based onthe multiple output and single-ended flyback switch power structure was designed.This charger used the double closed loop control mode that combined with front endanalog control and back end digital control, through the front end based on UC3842driving controller’s controlling to output total power, which ensured that the chargercould work in a safe state under the condition of the end digital control becoming invalid; through the digital controller of back end using microcomputer as its core toprecisely control output current, voltage, which ensured the stability of the charger’soutput characteristic. After the completion of charger’s hardware design, a controlstrategy based on PWM-PFM and the charger output power control algorithm with thecorresponding control softwares based on simplifing fuzzy PID control were designed.Finally, after completing the design of intelligent charger, for the convenience ofthe charger’s test and its later batch production test, a charger monitoring moduledesign plan was also put forward in this paper. Through laboratory test and enterprisesmall batch trial production, the test results showed that the design was reasonable andright, each module of charger worked normally, and had significant positive impact onthe service life of the battery.