Design Trade-Offs and Selection Guidelines for Isolated and Non-Isolated Converters for In-Motion-Charging Buses
R. F. P. Paternost (Unicamp, Campinas, Cidade Universitária)
R. Mandrioli (University of Bologna)
I. Diab (TU Delft - DC systems, Energy conversion & Storage)
M. Bartłomiejczyk (Gdansk University of Technology)
M. Ricco (University of Bologna)
T. A. S. Barros (Unicamp, Campinas)
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Abstract
The increase in electrified transport has elevated the role of electric buses (e-buses) in addressing urban mobility challenges. Among the types of e-buses, there is the in-motion-charging (IMC) trolleybus, which is powered by DC overhead contact lines and has an on-board battery for traction outside overhead lines. A key challenge for IMC buses is the selection of the optimal on-board-charger (OBC) topology for charging their batteries. Ideally, the chosen OBC should have low weight and volume, in addition to operating with high efficiency levels. Additionally, there is a growing need for isolated DC-DC converter topologies to enhance safety and reduce the risk of electric shocks. However, the isolated topologies tend to have higher volume and weight and reduced efficiency due to the need for a high-frequency transformer (HFT). In this context, this article aims to provide design trade-offs and guidelines for choosing between isolated and non-isolated topologies for OBC in IMC trolleybuses, based on an analysis of their efficiency, weight, volume, and cost. A non-isolated interleaved buck-boost (IBB) and an isolated dual-active-bridge (DAB) converters are taken as the study-case. Results indicate strong potential for the IBB at switching frequencies above 75rm kHz, primarily due to a significant reduction in the weight and volume of the magnetic components, with the weight of IBB being about 0.84 times that of the DAB at 100rm kHz switching frequency. For lower frequencies, the DAB converter presents advantages in terms of magnetic compactness. The efficiency of both topologies remains at similar levels, with a slight advantage for the non-isolated one, achieving an average efficiency of up to 99.07%.
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