Design and Implementation of Lead Acid Batteries Charger with Energy Recovery and SOC Estimation

• Main Authors: Te-Wei Wang, 王德緯
• Other Authors: 徐國鎧
• Format: Others
• Language: zh-TW
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/76223327921204106289

碩士 === 國立中央大學 === 電機工程研究所 === 95 === This thesis proposes a new rapid charger based on a fuzzy state-of-charge (SOC) estimation in Reflex TM charging method for the sealed lead-acid battery of the electric vehicle (EV). It includes an energy recovery stage which can save energy instead of conventional one which uses static resistance to discharge the batteries. The efficiency of conversion is up to 85% and power factor is up to 0.99. Charging time from SOC 0% to 70% is about 10 minutes. Moreover, this thesis proposes a novel fuzzy SOC estimator which uses normalized parameter and open circuit voltage to estimate SOC of batteries accurately. In the high current charging, the proposed SOC estimation can avoid a situation of undercharge or overcharge; note that the overcharge will shorten the battery lifetime. The charging control and the SOC estimation are based on fuzzy theorem, implemented by a digital signal controller (dsPIC30F6010). The SOC of batteries is estimated while the system is charging the battery and the estimated error is maintained within an acceptable range (±5%). The thermal rise can also limited under 8°C to avoid damaging the batteries. Moreover, this system uses an equivalent internal resistance to calculate the internal resistance of the batteries. During the Reflex TM charging, the controller can self-tune the discharging time according to the internal resistances, which reduces the thermal rises and the lifetimes for the batteries. Finally, experimental results are provided to verify the performance of the system and the feasibility of the proposed SOC estimation in this thesis.