48 V Power Net
Facing the challenges of further efficiency improvement and steadily declining CO2 limits in the automotive sector, the importance of power net development has grown continuously. In addition to the initially dominant demand for a reliable energy supply for the electrical components and a sufficient battery charge, other aspects are becoming more and more relevant. The increasing demand for electrical energy, new comfort and assistance functions, the electrification of auxiliary systems, as well as the automated driving require new impulses in the area of electrical systems and the electrical energy management.
In particular, dual battery and dual voltage power supply systems in the low-voltage range promise significantly increasing efficiency without large technological or financial efforts. Depending on the vehicle segment either an extension of the established 12 V micro hybrid technologies or new 48 V mild hybridization concepts are conceivable. Both technologies offer an increased recuperation capability, improved stop-start systems, new functionalities such as sailing or boosting and need minor adjustments of the drive train. However, they require a lot of further developments in the field of energy management to enable efficient power.
HiL Test Bench for Automotive Power NetsCopyright: © RWTH Aachen | VKA
For this purpose, a Hardware-in-the-Loop (HiL) test bench for automotive power nets has been developed at the Center for Mobile Propulsion. By its flexible concept the test bench gives the necessary degrees of freedom for an effective power net development. An adjustable belt drive allows to test a wide range of energy converters from a conventional alternator up to a 48 V belt-driven starter generator. On the electrical side variable dual battery topologies can be simulated. Furthermore, controllable loads can emulate any electrical consumers up to a maximum load current of 1050 A. High-precision measurement technologies provide all relevant mechanical and electrical parameters. The power net test bench is coupled via a dSPACE Scalexio HiL simulator to the virtual test environment. In addition to the test bench control, the vehicle simulation including the electrical energy management is carried out in real time on the simulator. The main interface to the mechanical test bench is the speed and load behavior of the drive machines, directly affecting the electrical system by the belt-driven starter generator.
The Hardware-in-the-Loop test bench for automotive power nets offers the necessary toolchain for an application-oriented development of electrical energy management functions based on variable load scenarios in realistic driving cycles. Moreover, valid statements on the performance of components, but also on the electrical energy balance and voltage stability of the power supply system can be made by replicating the physical power net.
Thus, the HiL test bench complements the development process and enables a considerable potential for time and cost saving through the virtualization of individual development tasks. An iterative combination of Model- and Hardware-in-the-Loop approaches can furthermore be used to increase the maturity in an early phase of the development. In this context the quality of modelling can be significantly improved on the basis of test bench measurements by test bench based optimization of the model environment. In order to meet the requirements for efficient frontloading a consistent software architecture is necessary, which uses standardized model and component interfaces. The model-based software architecture FEV PERSIST creates a cross-platform toolchain that allows a seamless software development from the simulation to prototype or serial application.