%0 Journal Article
%T Improving Energy Conversion Efficiency by means of Power Splitting in Dual Drive Train EV Applications
%A Michael A. Roscher
%A Roland Michel
%A Wolfgang Leidholdt
%J International Journal of Vehicular Technology
%D 2013
%I Hindawi Publishing Corporation
%R 10.1155/2013/398361
%X The limited amount of energy stored on board of battery electric vehicles (BEV) spurs research activities in the field of efficiency optimization for electric drive train applications in order to achieve an enhanced mileage. In this work a control method for BEV applications with two drive trains (e.g., one at the front and one at the rear axle) is presented. Herein, a simple optimization algorithm is introduced enabling to operate the two drives with different torque values, depending on the instantaneous operation point, leading to a reduction of apparent power losses on board. Simulations on a virtual BEV yield a decrease in the cumulated energy consumptions during typical BEV operation, leading to an increase in the achievable mileage. 1. Introduction In recent years, the need for zero emission transportation spurred the broad market introduction of battery electric vehicles (BEV). BEVs can play a key role on the way to the environmentally conscious society [1]. Especially in mega cities where air pollution is a critical, the emission free vehicles can contribute to improve the health-related quality of life. Moreover, if the energy for battery charging comes from renewable sources (wind, solar, hydro power, etc.), the vehicles operate almost 100% CO2 neutral. However, one main drawback of battery powered vehicles is the very limited range, due to the very limited amount of energy stored in the battery. On the one hand, the efficiency of energy conversion of electric power trains is 2-3 times higher ( ) than the efficiency of combustion engines ( ¨C40%). On the other hand, the nowadays commercial battery cells comprise energy densities of maximum 250£¿Wh/kg [2], which is less than one fortieth of the theoretical energy density of conventional fuels (petrol gas approx. 12.000£¿Wh/kg). Moreover, the energy density of common battery systems is reduced about almost one-half, due to efforts for housing, cooling, and integrated electrics/electronics. An electric drive train substituting the combustion engine is one possible vehicle concept. Besides, various approaches (e.g., four separate in-wheel drives) are possible. In the following a vehicle architecture including two drives (i.e., one at the front and one at the rear axle (¡ú 4£¿WD); see Figure 1) is exemplarily considered. Figure 1: Power supply architecture of a two motor BEV concept. In the illustrated BEV architecture the HVAC or at least the integrated compressor is supplied directly from the battery. To supply additional aggregates, the battery voltage is transferred into, for example, 12£¿V by a
%U http://www.hindawi.com/journals/ijvt/2013/398361/