A Novel Approach for Sizing Battery and Supercapacitor for FCEV

Abstract

The objective of this paper is to present a new approach based on Dynamic Programming (DP) to solve the problem of sizing of lithium-ion battery and supercapacitor for a Fuel Cell Electric Vehicle (FCEV). The powertrain of FCEV essentially comprises of a fuel cell stack and a DC/DC converter cascade along with its auxiliary subsystems, a Li-ion battery, and a supercapacitor cascaded to the powertrain via its DC/DC converter rendering the hybrid energy storage system in a semi- active configuration. The optimal sizing of battery and supercapacitor of the powertrain is arrived at by solving an integrated optimization problem that minimizes fuel consumption and degradation of the battery for a specified drive cycle used in the reported literature. The Dynamic Programming (DP) problem has an objective function to minimize the weighted fuel consumption, (i.e., the hydrogen consumption) along with the battery capacity loss i.e., maximization of battery life and better utilization of the battery. This is achieved in terms of throughput of and stress on the battery by the virtue of limiting the power transients/C-Rates while sustaining the battery charge at the end of the drive cycle. The DP problem is solved for a range of killoWattHour capacity rating of battery and supercapacitor. A heuristic layer outside the DP framework ensures the sizing of the battery and supercapacitor that effectively meets the objectives of arriving at the size of the battery and supercapacitor for economic Hybrid Energy Storage System (HESS). This novel approach could be easily extended to multiple standard drive cycles and real-life drive cycles.