中文摘要：

在混合动力电动汽车巡航工况时，为了降低油耗和延长电池的使用寿命，对其能量管理策略的优化除了考虑发动机和电动机工作点的优化之外，还应考虑电池工作点的优化。针对这个问题，建立一种具有无级变速结构的轻度混合动力电动汽车的纵向动力学方程，在此基础上综合考虑发动机、电池、电动机与传动系统的效率，分析车辆巡航工况下的系统效率，得到系统效率优化的目标函数和约束条件。随后利用序列二次规划算法对轻度混合动力电动汽车系统效率进行优化计算，从而确定车辆巡航工况下的最佳蓄电池功率和最佳无级变速器（Continuously variable transmission，CVT）减速比。优化结果揭示出驱动系统的特性，可为驱动系统的优化奠定基础。

英文摘要：

When the hybrid electrical vehicle is cruising, in order to reduce the fuel consumption of the engine and improve the service life of the battery, the work areas optimization of the engine and motor is considered in the energy management strategy of hybrid electrical vehicle. At the same time, the work areas optimization of the battery is considered too. Aiming at this problem, the longitudinal dynamics of a mild hybrid electric vehicle with continuously variable transmission（CVT）is firstly analyzed. And then, the efficiency of total system under different cruise conditions is studied by comprehensively considering the efficiencies of the engine, motor, battery and transmission system. After the objective function and constraints are obtained, the sequential quadratic programming （SQP） algorithm is applied to the optimization of system efficiency for the mild hybrid electric vehicle. At last the optimal battery power and optimal speed reduction ratio are found for different cruis e conditions. The optimization results show the characteristics of the drive system, and these results can lay a foundation for the optimization of the drive system.