A Study on Optimal Operation Strategy for Mild Hybrid Electric Vehicle Based on Hybrid Energy Storage System

  • Bae, SunHo (School of Electrical and Electronic Engineering, Yonsei University) ;
  • Park, Jung-Wook (School of Electrical and Electronic Engineering, Yonsei University)
  • Received : 2017.10.16
  • Accepted : 2017.11.13
  • Published : 2018.03.01


This paper proposed an optimal operation strategy for a hybrid energy storage system (HESS) with a lithium-ion battery and lead-acid battery for mild hybrid electric vehicles (mild HEVs). The proposed mild HEV system is targeted to mount the electric motor and the battery to a conventional internal combustion engine vehicle. Because the proposed mild HEV includes the motor and energy storage device of small capacity, the system focuses on low system cost and small size. To overcome these limitations, it is necessary to use a lead acid battery which is used for a vehicle. Thus, it is possible to use more energy using HESS with a lithium battery and a lead storage battery. The HESS, which combines the lithium-ion battery and the secondary battery in parallel, can achieve better performance by using the two types of energy storage systems with different characteristics. However, the system requires an operation strategy because accurate and selective control of the batteries for each situation is necessary. In this paper, an optimal operation strategy is proposed considering characteristics of each energy storage system, state-of-charge (SOC), bidirectional converters, the desired output power, and driving conditions in the mild HEV system. The performance of the proposed system is evaluated through several case studies with respect to energy capacity, SOC, battery characteristic, and system efficiency.


Supported by : National Research Foundation of Korea, Korea Institute of Energy Technology Evaluation and Planning (KETEP)


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