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

Abstract

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.

Review and Development of Electric Motor Systems and Electric Powertrains for New Energy Vehicles

“…The system efficiency was improved by optimizing the configuration, e.g., by adding gears to components or gearboxes with several transferring ratios [70]. To solve the working area mismatch between the engine and the motor, a new multi-mode coupling drive system was designed by coupling a distributed drive system with a centralized drive system and adding a clutch [71].…”

Análise Cinemática para uma caixa de engrenagens planetárias aplicadas em veículos híbridos e elétricos

“…Furthermore, Zhang et al [16] raised all the possible operation modes of simple PG with the removal and addition of clutches in Chevy Volt and Toyota Prius models, evaluating their performance. Moreover, many analyses are possible, as the kinematic and torque formulation proposed for different types of planetary gear sets by Amaral [17], the dynamic programming and the Genetic Algorithm to obtain better efficiency in seriesparallel HEVs shown by Kabalan et al [18] and the method to evaluate the efficiency of gear transmission in a PG provided by Petrescu et al [19]. Besides, Morais [20] and Kouroussis, Dehombreux and Verlinden [21] shows some application in automatic gearboxes.…”

Systematic Methodology for Architecture Generation and Design Optimization of Hybrid Powertrains

“…In [6] a gearbox is inserted between the Engine (ICE) and the Motor Generator (MG). Different topologies of seriesparallel HEV made by adding gears and gearboxes are studied in [7]. The location of the MG can also be changed and improved as in [8].…”

“…The components used correspond to a middle class HEV [7]. The components are sized through a scaling technique [7][35].…”

“…Their initial main characteristics are presented Table 3. The engine specific fuel consumption and MGs efficiencies maps can be found in [7]. The sizing variables are scaling factors applied to the maximum power of the ICE, MG1 and MG2, the modules number in the battery and all the involved gear ratios (6).…”