Smart and Hybrid Battery Balancing For Electric Vehicles
Authors: de Castro, Ricardo and Araujo, Rui Esteves and Barreras, J.V. and Pinto, C.
21st IFAC World Congress, Berlin, Germany.
Battery packs of electric vehicles are prone to capacity, thermal, and aging imbalances in their cells, which limit power delivery to the vehicle. Spurred by this issue, we propose a new class of battery balancing systems, called hybrid battery balancing, capable of simultaneously equalizing battery capacity and temperature while enabling hybridization with additional storage systems, such as supercapacitors. Our research departs from the current research paradigm, which regards battery equalization and hybridization as two independent functions performed by two separated power converters. In contrast, our concept integrates these two functions into a single system, paving the way for a lower cost of power conversion in hybrid energy storage units. In exchange for reduced hardware costs, this integration of functions poses challenges to the design and control of the hybrid system, such as simultaneously coordinating a large number of power converters, enforcing actuation and safety constraints and making trade-offs between multiple technical and economic objectives. To handle these challenges, we developed constrained and hierarchical optimal control frameworks that rely on convex formulations as a means to obtain computationally efficient control algorithms. Through validation in small scale prototypes, we have demonstrated that this hybrid balancing concept can significantly decrease energy losses and battery stress while increasing a vehicle’s range when compared with conventional balancing methods