A comparison of system architectures for high-voltage electric vehicle batteries in stationary applications

An increasing global interest in clean energy alternatives requires new concepts for local storage of electricity. This leads to new research demand regarding suitable system architectures based on high-voltage batteries from electric vehicles. In this study, a new method for evaluating stationary system architectures is described. The assessment focuses on the system efficiency of different architectures. A sensitivity analysis is included to show further distinctions in criteria such as volume, weight and cost. Three system topologies for the use of new and second-hand batteries extracted from electric vehicles in stationary applications are presented. All components need to be able to operate in a bidirectional mode - the ability to absorb and release electricity from and into the grid. The first two topologies include one battery connected to the grid either with a DC/DC converter and a DC/AC inverter or with a DC/AC inverter and a transformer. The third topology involves the connection of two batteries in series with a DC/AC inverter, providing better characteristics in terms of the required power electronic components. The results show differences between one to two percentage points in efficiency. Moreover, the influence of parallelisation and various power distributions delivers close to five percentage points higher efficiency for the first topology with a DC/DC converter. Combined with the outcome of the sensitivity analysis, the topology with the DC/DC converter connected to the DC/AC inverter exhibits the best performance in the overall evaluation criteria.