具增程效應之全域式主動平衡模組開發

DEVELOPMENT OF A GLOBALLY ACTIVE BALANCE MODULE WITH RANGE EXTENSION EFFECT

林正乾(Jeng-Chyan Muti Lin)

電池管理系統 ； 平衡模組 ； 鋰離子電池 ； 增程效應 ； BMS ； balance module ； lithium ion cell ； range extension

技術學刊

32卷4期（2017 / 12 / 01）

275 - 282

繁體中文

包括磷酸鋰鐵電池在內的鋰離子電池具有高能量與功率密度的優點，但鋰離子電池芯串聯時因為電芯間的不一致需要電池管理系統進行電芯間電壓的平衡，當單電芯過充或過放時電池管理系統需切開充電器或負載進行保護，切離保護則會造成電池組的有效蓄航力降低。本論文探討使用二段式均充電法與使用獨立平衡電源之放電平衡策略來解決部分電芯充電時提早過充或放電時提早過放之問題，進而達到電動載具增程的效應。本文所使用的充電平衡與放電平衡都是植基於全域式的主動式平衡電路，二段式均充電法包括平衡串充與分充兩階段，目的在達成串聯的電芯都充飽電且無過充，放電平衡則是提早找出將過放之電芯並藉外部獨立電源補充最弱電芯電能，目的在達成延遲最弱電芯提早過放，有效利用所有電芯所儲存的電能，進而達到充電與放電皆具增程之效果。本文將所開發具增程效應之全域式主動平衡電路建構在一48 V的模組電池管理系統上，增程的效應則由一台自製的96 V三輪電動載具進行評估與驗證，道路實測的結果驗證本文所提出的充放電策略可以達到明顯的增程效果。

Lithium ion cells, including lithium iron phosphate (LFP) cells, possess high energy density and high power density. However due to discrepancies in cell internal resistance and aging process, cell voltage and capacity imbalance are common among cells in series connection or battery module. Lithium ion batteries therefore require an effective battery management system to avoid overcharged or over discharge states resulted from cell imbalance via active protection. Nevertheless, electronic protection strategy reduces effective ranges and might acerbate cell imbalance degree. This study manages cell imbalance problem in both charging and discharging stages respectively based on the same globally active balance module. A two-staged charging and balancing scheme compensates cell inconsistency in the charging stage and evenly charges each cell to a full state without the shortcomings of existing balance methods. A selective balance method in discharging state counterbalances cell imbalance via an external power source injecting balance current to weakest cell in the series. Balance measures in both charging and discharging stages adopted by the current study are aimed at extending ranges for the vehicles served by proposed balance module. The proposed globally active balance module is integrated with a 48 V module BMS and range extension effects are evaluated by experiments with lab instruments and field tests on a 96V prototype tricycle. Test results show the proposed balance method employed both in charging and discharging stages has the advantage of promoting range extension.

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