Hierarchical Power Management System for a Fuel Cell/Battery Hybrid Electric Scooter

A green hybrid electric scooter (HES) with a proton exchange membrane fuel cell (FC) as the primary energy storage system (ESS) and a lithium-ion battery (LIB) as the other assistant ESS is developed in this study. A hierarchical power management system (HPMS) is proposed to control the power flows of dual ESSs within the HES to achieve preferable energy utilization efficiency. A rule-based control (RBC) strategy is first designed in the upper power optimization layer. Subsequently, a global search algorithm (GSA) and a Cuckoo search algorithm (CSA), which both consider the information including the state-of-charge of LIB, total demanded power of the HES, and efficiencies of the FC, LIB, and power converters, are proposed for optimizing a power split ratio parameter, thereby ensuring optimal power allocation for the HES. In the middle power allocation layer, the current commands of both dc-dc converters connected to the ESS are individually determined. Finally, semi and fully-active hybrid powertrains with voltage and current control loops are designed in the lower power control layer to regulate the practical drive currents and the dc bus voltage. Results demonstrate that the HES can obtain promising endurance and speed tracking performances by using the proposed fully active hybrid powertrain (FAHP) with the CSA strategy.