Switching frequency optimization for a solid state transformer with energy storage capabilities

摘要

This paper is focused on establishing a procedure for measuring the efficiency dependency on the switching frequency for a solid state transformer (SST), being one of the ports connected to an energy storage device (Lithium-Ion battery). Multiple contributions for measuring the efficiency/losses for different power converter structures for energy storage applications can be found in the literature. However, there are few references which consider the effects of the high frequency model of the battery in the complete system performance. This research will obtain a parametric high frequency model of the battery cells, based on a vector fitting method in frequency domain. This model will be used for the estimation of the overall system losses. It will be demonstrated that the contribution of the battery losses, as well as its behavior as a function of the switching frequency, can significantly affect the selection of the converter's switching frequency.