不受電池老化影響之電感式平衡控制研究

Abstract

本論文提出了不受電池老化影響之電感式平衡控制機制，會對應電池的不同老化程度選擇適當的平衡啟動時機，並控制適當的平衡電流，使電池的平衡能確實達到平衡電池電壓以及增加電池組儲存電量的效果，並藉由提升電池的放電深度來減緩電池的老化速度。在電池串聯使用的情況下，由於電池之間老化程度的差異，使電池電壓產生不一致的現象，造成電池有過充的危險，並會使電池組充入的電量降低，因此需要對串聯電池組進行平衡。但並非在不同的充電階段對電池進行平衡其結果都是有益的，以磷酸鋰鐵電池為例，電池的電壓在平坦區與最後充電階段其電壓對電量的上升速度差異非常大，在電壓平坦區進行平衡時，由於電池老化程度的不同會造成電壓差，但平衡造成的電量改變所反應的電壓變化非常小，因此難以使電池的電壓達到一致，且無法藉由電壓判斷電池的電量狀況，持續進行平衡反而會導致電池的電量產生嚴重的不平衡，而本論文提出的平衡控制機制即是為了避免在不應該啟動平衡的時候進行平衡，使電池平衡管理能確實達到平衡的效果。經過實驗的比較，使用此平衡控制機制可使新電池增加8.4%、老電池增加3.6%的充入電量，而傳統的平衡方式雖然也能使新電池增加8.3%的電量，但卻會使老電池減少2.7%的電量，反而會降低電池組能放出的電量，並導致電池的老化速度加快；證明並非任意的進行電池平衡都是有益的，需要對是否啟動平衡進行控制才能使電池的平衡管理獲得較佳的效果。

This thesis proposes an aging-free balancing control mechanism, which will select the appropriate balancing control according to the different levels of cell aging. The equalization can balance the voltages between batteries and increase the total available charge indeed. When the batteries are charged in series, the difference of the aging degree among batteries leads to the imbalance of the battery voltages. This imbalance decreases the capacity and lifetime of the batteries. Therefore, the battery pack needs an equalizer to solve the problem. But balance at the different charging stages not always leads to beneficial result. Take Lithium iron phosphate battery for example. The difference of the voltage change rates between the plateau stage and the final charging stage is very large. When charging in the plateau stage, the degree of aging of battery causes the voltage difference primarily. However, the voltage variation caused by the charge changing by the equalization is quite small. It is difficult to make the voltage the same. Continued balancing will eventually lead to much more serious imbalance. Experimental results that the balancing control mechanism can makes the new battery increased 8.4% storage capacity and makes the aging battery increased 3.6% storage capacity. The conventional equalization can makes the new battery increased 8.3% storage capacity but makes the aging battery decreased 2.7% storage capacity. The experimental results prove that balance at different stages not always be beneficial. Using the aging-free balancing control mechanism can obtain a better balancing effect.