Maximum-Current Curve Operation of Electric Vehicles for Improved Energy Recuperation during Regenerative Braking

This article introduces a novel approach to maximize the harvested energy during regenerative braking in electric vehicles (EVs) through an optimal distribution between regenerative and friction braking. In the proposed method, the optimum operating point of the electric motor during braking is determined based on the driver's brake request and real-time vehicle speed. To this end, a maximum-current curve (MCC), which represents the maximum current that can be recaptured during braking for a given resistive torque, is introduced, and the electric motor operating point is maintained on this curve. In this method, energy extraction during the regenerative braking process is maximized due to operation on the MCC, which also leads to an extended effective range for regenerative braking compared to traditional methods. The effectiveness of the proposed approach is experimentally investigated on a hardware-in-the-loop (HIL) EV testbench. It is observed that for a predefined drive cycle, an increase of 12.4% in harvested energy can be achieved by implementing the proposed method compared to a case where traditional brake distribution is used. Potential gains in the effective driving range of EVs as a result of increased energy recuperation can pave the way toward a more rapid and widespread adoption of EVs.