Partial Power Converter for Electric Vehicle Hybrid Energy Storage System Using a Controlled Current Source Cascade Architecture

Abstract

The energy sources in a Hybrid Energy Storage System are coupled by a DC-DC converter. Nevertheless, this device's mass is irrelevant when evaluating the performance of such a system in terms of density, so it must be reduced to achieve maximum performance. This can be achieved with the solution presented in this paper: a coupling architecture based on a controlled current source, in which the DC-DC converter's processed power depends on the voltage difference between the two sources. If this difference is zero, so is the power processed by the converter. Minimizing this power leads to a reduction of the converter's mass and volume, increasing system performance. In this paper, the controlled current source cascade architecture combines two lithium-ion batteries to supply a limited-range electric vehicle. Its operation is addressed and validated by simulation and experimental results. For the experimental validation, the batteries and the load were emulated by power supplies, with a 2 kg, 3.3 kW evaluation board serving as DC-DC converter. The findings reveal that the examined architecture enables a substantial reduction in the converter's sizing power, up to a factor of 14 compared to a conventional solution commonly seen in the literature.