Revisiting the Partial Power Processing Concept: Case Study of a 5-kW 99.11% Efficient Flyback Converter-Based Battery Charger

This article proposes an analytical methodology to evaluate the performance of the main partial power processing (PPP) architectures in terms of the improvements in the system's conversion efficiency. This analysis considers the influence of the system's voltage gain, the auxiliary dc/dc converter's efficiency, and the possibility of bidirectional power flow. Herein, the key PPP architectures are, thus, modeled and benchmarked. The presented results attest to the series configuration as the most efficient PPP circuit solution, with no limits on the system voltage gain, contrary to the generalized results found in today's literature. To assess these results and the significance of the proposed analysis, a well-known, simple, and cost-effective flyback topology has been designed and tested for a series PPP circuit solution able to effectively interface a 5-kW battery energy storage system (BESS) to a 700-V dc grid. A relatively high power conversion efficiency and compact hardware are achieved due to the reduced size requirements on the input and output filtering stages. Above all, while explaining the PPP concept, this study shows that even converter circuits known for their low power efficiency can be used to derive highly efficient systems. A design approach is, thus, provided to facilitate the design of the presented PPP circuit, and measurements are, finally, carried out to compare the obtained results with the expected ones derived from the developed analytical models.