- 學位論文
以等效內阻法進行電池系統SoC損耗修正
Estimation and Modification Battery Power Loss by Equivalent Internal Resistance Method
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摘要
本研究主要目的是建立一套可用於本研究室所研發的電動車”Green Jumper”的電池系統SoC估算技術。並以等效內阻估算電池芯於各種充放電條件下的效率損耗，以修正舊有的庫倫修正法因無法反應電池芯效率值而造成的計算誤差。 目前有許多方式可估算電池的SoC 值，其中庫倫積分法常被使用於電動車輛等需要進行大功率變動輸出的電池系統。但由於電池芯的效率並非100%，因此單純針對電流進行積分會於每次計算中產生誤差累積，造成估測精準度的下降。因此在使用庫倫積分法時需要對電池效率進行實驗與修正。但由於電池芯的效率與許多參數有關(如電流、溫度、壽命等)，各參數之間又會相互影響，所以必須要依照各種條件進行非常大量的實驗並建立複雜的查表程式，因而造成研究時間與成本的大幅增加。為了解決此問題，本研究建立一套新式的演算法，以即時估算的方式對電池芯的效率損耗進行估計，以減少估算電池效率時所需的實驗數目。 由於會影響電池芯放電效率的各項參數並非相互獨立，而這些參數的變化則會直接反應在電池芯的內阻值上，並產生overpotential的現象。因此本研究藉由即時量測電池芯充放電時的overpotential數值，以估算其等效內阻的變化與目前電池芯的效率損耗。在得出電池的效率損耗後，便可將其帶入庫倫積分法進行修正，計算出電池芯的SoC值。 本研究會先建立一套演算法用以估算電池的等效內阻與效率損耗。接著將此演算法寫入BMS內，並安裝至實驗機台進行放電測試。最後則是將其安裝至實際的電動車進行道路測試，以確認該演算法在複雜的使用環境下依舊可以有較好的SoC 估測精度。在進行過上述實驗後，已證明本研究的等效內阻估測法可以確實修正電池芯的效率損耗值，並於大部分的放電條件下可將誤差值控制於1%以內。而且於實車道路測試的狀況下依舊可以正常作動，並且保有較佳的估測精準度。
並列摘要
This paper describes a state of charge (SoC) indication method for the battery system of an electric vehicle “Green Jumper”, which has been developed in National Taiwan University. In this new SoC indication method, power loss computing algorithm, Coulomb counting and EMF-versus-SoC curve methods are combined to improve the accuracy. The core idea of this method is the power loss computing algorithm, which is calculated from battery equivalent internal resistance. Because the equivalent internal resistance of the battery cell varies from status and environment, thus it is designed in the proposed algorithm to be computed from its overpotential behavior in different charge or discharge states. The SoC indication method in this paper corrects Coulomb counting method by calculating the power loss value and hence the accuracy of SoC indication can be improved. The algorithm has been installed in a battery managing system and tests have shown that the performance is in good agreement with the design target. The algorithm will be installed in a battery managing system in the Green Jumper EV for on road test.
參考文獻
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