Analysis of dissipative losses in modular reconfigurable energy storage systems using systemC TLM and systemC-AMS

Battery storage systems are becoming more popular in the automotive industry as well as in stationary applications. To fulfill the requirements in terms of power and energy, the literature is increasingly discussing electrically reconfigurable interconnection topologies. However, these topologies use switching elements on the cell and module level that exhibit an electric resistance due to their design and hence generate undesirable dissipative losses. In this article, we propose a new analysis and optimization framework to examine and minimize the losses in such topologies. For this purpose, we develop a SystemC model to investigate static and dynamic load scenarios, e.g., from the automotive domain. The model uses SystemC TLM for the digital subsystem, SystemC-AMS for the mixed-signal subsystem, and host-compiled simulation for the microcontroller executing the embedded software. Here, we analyze the impact of the dissipative losses on the system efficiency that depend on the modularization level, implying the number of serial and parallel switching elements. Our analysis clearly shows that in reconfigurable topologies, the modularization level has a significant influence on the losses, which in our automotive example covers several orders of magnitude. For the topologies we have investigated, the highest efficiency can be reached when a parallel-only modularization is aspired and the number of serial switching elements is minimized. It is also shown that the losses of the state-of-the-art topology with one battery pack protection switch are almost as high as in a smart cell approach in which each energy storage cell has its own switching element. However, due to the high number of switching elements, this results in a reduction of energy density and increases the system costs, showing that this is a multi-criteria optimization problem.