Analysis and simulation of a 42V power system for automotive applications

the increasing demand for more fuel efficiency and environmentally friendly cars coupled with the consumers' drive for more comfort, safety and luxury has led to the introduction of more electrical and electronic systems in the passenger car. This is further impacted by the current trend in automotive industry to replace mechanical and hydraulic systems with their electrical counterparts. The handling capability of the current 14V DC system is getting very close to reaching its limits. To meet the new growing electrical power demands with minimum fuel consumption and minimum environmental effects, the automobile industry is looking into increasing the present voltage threefold, from 14V to 42V for future cars. In this paper, a detailed mathematical model for a 3-phase bridge rectifier, 4kW/42V power system, Lundell alternator average electrical equivalent circuit will be presented along with the alternator performance curves and analyse of the effect of the converter commutation on the supply current characteristics. The developed 42V automotive power system is implemented using control-oriented simulators (Matlab\Simulink) modelling techniques to assess the effectiveness of the model and its transient behaviour. The dynamic behaviour of the alternator in terms power, voltage, load/supply currents to sudden load changes is presented. In addition, the design of a voltage limit circuit to minimize the load-dump and supply current transients will be discussed.