Experimental investigations on voltage stability in multilevel power nets

In recent years, more and more components in vehicles have been electrified in order to improve the safety and comfort of the passengers as well as the driving performance. Owing to these developments, it has become increasingly difficult to guarantee the voltage stability within the 12 V as well as the high voltage power bus. However, a new degree of freedom arises, as the two power nets are connected in order to exchange energy. As a consequence, they are able to stabilize their voltage reciprocally. This paper deals with the analysis of how two voltage levels can be coupled actively in order to stabilize their voltages in power demanding situations. A power net test bench consisting of a 12 V power net and a high voltage power net is built. In the 12 V power net, original chassis and wiring harness are used in order to achieve the most realistic behavior. Furthermore, there are two control modes presented. In the power control mode, the power flow is increased preventively when the prediction model detects a critical situation that is likely to occur in the near future. In the voltage control mode, the voltage controller of the DC chopper converter is used to stabilize the power net voltage in real time. Both control methods can easily be implemented into a universal power distribution management system. The voltage control mode is experimentally investigated at the power net test bench and it is shown that the minimum voltage in very power-consuming driving situations is increased by about 1.5 V per 1000 W of applied power supplied by the DC chopper converter.