Model-Based Analysis of Transient Currents to Dimension a Vehicular Power System With Electronic Fuses Regarding Short Circuit Selectivity

A fail-operational vehicular power system requires the selective tripping of electronic fuses (eFuses) in case of a fault event, e.g. short circuit, impermissible wire temperature. As a result of a short circuit and the associated interruption of the fault current by an eFuse, transient currents within the vehicular power system commutate into neighboring paths and potentially cause an unintended tripping of other eFuses. In this paper, modeling of the vehicular power system and an analytical methodology using state-space systems are proposed to calculate the transient currents during a short circuit and switch-off process. Comparing the results of the new approach with data obtained from simulation and measurement revealed a sufficient accuracy to represent the current trajectories. Furthermore, the analytical methodology enables a significant runtime reduction compared to simulations. Using the methodology, a parameter study is done to examine the influencing parameters on the transient currents in a 12 V or 48 V vehicular power system, and to derive guidelines for accomplishing selectivity. Based on this knowledge, an exemplary dimensioning process of a vehicular power system with regard to selectivity is shown and the effect of the different parameters on the critical currents regarding selectivity is discussed. The fault isolation time and the current threshold of the tripping eFuse have shown to be crucial parameters to reduce the transient currents efficiently.