Efficiency Improvement of a Series–Parallel Hybrid Electric Powertrain by Topology Modification

Published in IEEE Transactions on Vehicular Technology, 2019

Recommended citation: B. Kabalan, E. Vinot, C. Yuan, R. Trigui, C. Dumand and T. E. Hajji, "Efficiency Improvement of a Series–Parallel Hybrid Electric Powertrain by Topology Modification," in IEEE Transactions on Vehicular Technology, vol. 68, no. 12, pp. 11523-11531, Dec. 2019, doi: 10.1109/TVT.2019.2952190 https://ieeexplore.ieee.org/document/8894384

Among Series-Parallel Hybrid Electric Vehicle (SPHEV) powertrains, the Power-Split architecture with a planetary gear has an exemplary energetic efficiency in mixed driving conditions. Nevertheless, a simple SPHEV architecture can be realized without a planetary gear. It consists of 2 Electric Machines (EM) mounted on the engine shaft and separated by a clutch. With no power-split operation, this architecture allows the vehicle to operate in pure electric, or series hybrid, or parallel hybrid mode. It was proven to be less efficient than a reference Power-Split SPHEV; the Toyota Hybrid System (THS). The aim of this paper is to investigate the potential of efficiency improvement of the simple SPHEV powertrain by topology modification: the addition of gears for the components or a gearbox with few number of ratios. Two new variants of SPHEVs are proposed. The versions of SPHEVs and the reference THS are optimized by a bi-level optimization technique using Genetic Algorithm and Dynamic Programming. Compared to the simple SPHEV, results show an efficiency worsening in one variant and an efficiency improvement in another variant with a fuel consumption comparable to the one of THS. A global sensitivity study is then performed on the worsened variant. The sensitivities of the added gears are determined and an elimination of some is suggested. A new variant with fewer gears is therefore proposed and optimized. The efficiency is improved but remains less than the one of THS.

Cite this work: B. Kabalan, E. Vinot, C. Yuan, R. Trigui, C. Dumand and T. E. Hajji, “Efficiency Improvement of a Series–Parallel Hybrid Electric Powertrain by Topology Modification,” in IEEE Transactions on Vehicular Technology, vol. 68, no. 12, pp. 11523-11531, Dec. 2019, doi: 10.1109/TVT.2019.2952190