Voltage Stability and System Behavior of Cybernetic Loads in Vehicular Power Nets

Voltage stability has to be ensured within automotive power buses in order to reliably supply all components with sufficient energy. Especially in modern vehicles (conventional, hybrid electric, or electric), the stability is endangered due to electric loads with high dynamics, for example chassis control systems. In this paper, a power distribution management based on cybernetic principles is described. To manage the power flow efficiently, it is reasonable to distribute some intelligence from the central control unit to the system’s components such as loads. A load’s control algorithm is presented that is able to fulfill the power management functions autonomously. Its stability is examined both in theory and in real cases. Therefore, evaluation criterions are derived from the component’s system behavior. Based on the algorithm’s equations, the transfer function is defined in order to proof the stability. Furthermore, over 200 test cases had been conducted and analyzed at a power net test bench that contains the whole vehicular power net, including wiring harness and chassis ground. The impact of all variables and influence factors on the stability is checked and, likewise, malfunctions are examined, such as measurement errors or data transfer with long dead times. By this means, the most critical variables could be detected. Based on the results, some improvements of the control algorithm are made and, as a result, a stable implementation is realized.