適應性磷酸鋰鐵電池組之健康狀態平衡

Abstract

在電池電力系統方面，平衡電池的健康狀態是很重要的一件事情，除了降低淘汰至二次使用的電池健康狀態差異之外，最重要的是可以提升電池於裝置中的可使用總電量。故此本論文提出適應性磷酸鋰鐵電池組之健康狀態平衡，在最大溫度差異5℃的環境下，以放電深度作為減緩老化速率的控制變因，並且使用控制迴路來避免需要極為準確的電池老化模型才能決定控制變因的比例，運用適應性的演算法決定適當比例常數並隨時調整，在並聯四組電池模組的模擬條件下，單就環境溫度不同的模擬結果可以增加14.0%的總可使用電量，同時存在不同溫度與不同容量下則可以增加13.3%的總可使用電量。在實作方面結合電量估測晶片與微控器及外部開關設計，在達成電池健康狀態平衡之外，為了避免電池陷入超出操作範圍之外的危險，於系統方面整合電池管理系統概念，免除電池進入過度放電或是充放電於過高溫的使用，整體提供完整電池健康狀態平衡與電池系統保護。實驗方面則是於無控制狀態下刻意擺放一組較為老化的電池，定電流放電與定電流後定電壓充電100次，證明並聯電池組並不會依據各自老化狀況增加的阻抗值來調適其老化狀態，其老化狀態則是會拉大差距。另一個實驗則是4組全新電池在利用放電深度來減緩其老化速率的控制迴圈下，充放電100次下，結果證明電池模組間最大老化程度差距確實逐漸拉近。

Equalizing SoH between batteries is a critical information for Battery Power System. It can not only decrease the SoH deviation between batteries, but also increase total available charge until end of life. To address this issue, this thesis proposes “On Adaptive SoH Equalization for LiFePO4 Battery Packs.” In temperature difference distribution of ≦5℃ from module to module, our SoH equalizer uses controlled DoD to slow the rate of capacity fading. By realizing adaptive control loop, we don’t need exact cycle-life model to determine DoD value. The appropriate control proportion K is determined by our adaptive control algorithm. Our controller can increase 14.0% available charge in simulation case with different temperature. Moreover, it can also increase 13.3% available charge in simulation case with both different temperature and capacity. The implementation includes SoH equalizer and battery management system. The platform provides both complete SoH equalization and Battery Power System protection. Experimental results that cycled an aged module and three fresh modules indicated that SoH gap between each module didn’t reduce. Other controlled experiment cycled 4 fresh modules, and result showed the SoH gap between each module was narrowed.