Series Architecture for the Reduction of the DC-DC Converter in a Hybrid Energy Storage System for Electric Vehicles

A Hybrid Energy Storage System (HESS) uses DC-DC converters to couple its energy sources. However, this device represents a "dead weight" in the system and must be reduced to a minimum in order to maximize the HESS' performance. This work proposes a new coupling architecture to reduce the converter's volume and mass. Not yet addressed in the literature, this architecture is based on a series coupling of the sources. In this case, a DC-DC converter is used to control the current difference between the two sources. If this difference is zero, so is the power processed by the converter. By reducing the power processed by the converter, its mass and volume can be reduced. Simulation and experimental tests were carried out to validate the architecture concept. For the latter, power supplies were used to emulate the batteries and the load, and a 2 kg, 3.3 kW evaluation board served as the DC-DC converter. The results show that, compared to a conventional solution that is usually adopted in the literature, with the series architecture, it is possible to reduce the converter sizing power by almost 3.7.