A thermal management system control strategy for electric vehicles under low-temperature driving conditions considering battery lifetime

Abstract

Electric vehicle thermal management system (EVTMS) is essential for electric vehicles (EVs) to guarantee cabin thermal comfort and battery appropriate temperature. However, under low-temperature driving conditions, heating power demand for EVTMS affects system performance as well as battery lifetime. In this context, an effective EVTMS solution both for cabin thermal comfort and battery heating is investigated in this paper. The EVTMS performance and battery-lifetime loss characteristics under low temperatures are analyzed. Moreover, a battery-lifetime extension method which reduces battery-lifetime loss by the peak shifting and valley filling effect for battery current is advanced. A novel EVTMS fuzzy control strategy based on this method is proposed to maintain the proper temperature range of cabin and battery, which also regulate the heater load considering battery current. Using an EV and EVTMS model validated by low-temperature driving experiments, the proposed strategy was investigated by simulation and the control effect was carried out. The results showed that compared with the original strategy, battery-lifetime loss with the proposed strategy was reduced by 3.11–3.76% while the average temperatures for the cabin and battery were almost unaffected. Therefore, the strategy can reduce battery degradation while meeting the cabin and battery heating requirements.