周美蘭 馮繼峰 張宇



Abstract:The composite energy storage system composed of battery, super capacitor and bi-directional DC-DC converter was studied to solve the problem of insufficient mileage and short battery life in electric vehicles. In order to realize rational power allocation of battery and super capacitor, the logic threshold and fuzzy control strategy were established respectively. The vehicle model was constructed based on the electric vehicle simulation software.Through simulation study,the characteristic curves of the current and SOC of battery and the current curves of super capacitor were got, and the results were compared with the single battery power supply. For verifying the feasibility and effectiveness of the control strategy, the experimental platform was built to study electric vehicles during driving and braking. Simulation and the experimental results show the composite energy storage system and its control strategies successfully reduce the charge and discharge current of battery, regenerate the braking energy and improve the mileage of electric vehicles.
Keywords:electric vehicles; composite energy storage; logic threshold; fuzzy control
0 引 言
近年來,隨著我國汽車保有量的急劇增加,石油資源逐漸匱乏、環境日益惡劣等問題也接踵而至,傳統燃油汽車造成的負面影響已無法滿足人們對可持續發展的要求,純電動汽車已成為今后的主要發展方向[1]。純電動汽車蓄電池的發展較為滯后,其功率密度較低、充放電次數有限、壽命較短,很難滿足人們的日常需求[2-3]。
為解決這一技術難題,在純電動汽車電源系統中安裝了超級電容和雙向DC-DC變換器,從而組成了復合儲能系統[4]。由于超級電容具有功率密度高、壽命長、能承受瞬時大電流充放電等優點,由此組成的復合儲能系統能夠提升原有電源系統的性能,從而提高純電動汽車的動力性能和續駛里程[5-7]。
隨著技術的不斷發展,復合儲能系統逐漸走進研究人員的視野,并已取得一些可喜的成就[8-9]。Chugoku電力公司和豐田公司對蓄電池和超級電容構成的復合儲能系統實驗研究,實驗結果顯示,相比單一蓄電池電源的電動汽車,具有復合儲能系統的電動汽車具有更好的動力性能[10]。Arani S K等人利用遺傳算法優化電動汽車模糊控制器并進行實驗,結果表明,所開發的模糊控制器在降低功耗等方面優于標準模糊控制器[11]。我國也開始對復合儲能系統進行各項研究[12]。如王斌等人提出了一種新型復合儲能系統結構,并設計了7種工作方案,有效提高了復合儲能系統工作效率并保證蓄電池的充放電安全[13]。Chen Jian等人提出了一種電動汽車用模糊邏輯參數調整的自適應控制方法,仿真和實驗結果證明了所提出方法的有效性[14]。但在能量回饋、蓄電池保護和電動汽車續駛里程等方面仍存在較大的缺陷。針對此類問題,本文提出了復合儲能系統的能量控制策略。
本文主要根據所選復合儲能系統結構設計了基于邏輯門限和基于模糊控制的能量控制策略。在AVL CRUISE仿真軟件中搭建了純電動汽車整車模型進行仿真分析,根據仿真分析的結果搭建了實驗臺架,從而達到驗證所設計的控制策略的可行性與有效性的目的。
1 復合儲能系統
復合儲能系統主要由蓄電池、超級電容和雙向DC-DC變換器等三部分組成。其連接方式一般可以分為以下幾種[15-16]:蓄電池與超級電容并聯、蓄電池串聯雙向DC-DC變換器后與超級電容并聯、超級電容串聯雙向DC-DC變換器后與蓄電池并聯、蓄電池和超級電容分別串聯一個雙向DC-DC變換器后并聯,這當中以第三種方式最為經濟實用且易于實現,其連接方式如圖1所示。
5 結 論
本文對復合儲能系統進行了研究,制定了兩種控制策略?;贑RUISE在NEDC工況下進行了仿真分析,搭建了純電動汽車復合儲能系統實驗臺架,進行了負載和制動實驗,得到結論如下:
(1)仿真結果表明,制定的純電動汽車復合儲能系統能量控制策略能夠合理地進行功率分配,使蓄電池輸出電流較為平穩,延長蓄電池使用壽命,同時超級電容還能有效地回收制動能量,提高能量的利用率。
(2)與單一蓄電池能源相比,邏輯門限控制策略總體節能6.17%,模糊控制策略總體節能34.57%;與邏輯門限控制策略相比,模糊控制策略節能效果提升5倍多,極大地提高了超級電容的利用率。
(3)負載與制動實驗表明,基于模糊控制策略的復合儲能系統能夠實現對回饋能量的有效利用,證明了所提控制策略的可行性。
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(編輯:劉素菊)