Sizing of Battery Converters for Residential PV Storage Systems

With the increasing number of domestic PV (photovoltaic) installations connected to battery energy storage systems for self-supply purposes in Germany, new research topics such as the sizing of the required system components have emerged. In this paper, the impact of the rated battery converter power on the utilization of PV-attached battery systems in residential buildings is discussed. First, the ratio between the battery converter rating and the storage capacity is analyzed for a variety of residential battery systems available on the market. Thereafter, simulations with a temporal resolution of 1 s are performed in order to identify how the rated battery converter power affects the energy throughput of the battery system taking account of the characteristic conversion efficiency curves. The results show that battery converter sizes in the range of 4 to 5 kW are optimal in terms of maximum discharged energy for the most system configurations under study. However, battery converters rated between 30 to 50% of the optimal power rating are sufficient to provide more than 95% of the maximum dischargeable energy from the battery system. Based on these findings, it can be concluded that small-sized battery converters rated at 1.5 to 2 kW are sufficient for residential self consumption applications.