Power Distribution Strategy of Fuel Cell Vehicle System with Hybrid Energy Storage Elements Using Triple Half Bridge (THB) Bidirectional DC-DC converter

A triple-half-bridge (THB) multiple-input bidirectional dc-dc converter was proposed recently to interface battery and ultracapacitor. This paper presents a power distribution control to coordinate the power partitioning among fuel cell, battery, and ultracapacitor when this THB converter is applied to the fuel cell vehicle system. A particular goal is to obtain both a peaking load control and state of charge control of battery and ultracapacitor. In order to analyze and verify the control strategy in the fuel cell system, some essential subsystem models were developed including small signal model of THB bidirectional dc-dc converter, simplified dynamic model of fuel cell, battery and ultracapacitor. The simulation results confirmed that the load leveling and state of charge control are effectively implemented. A 6 kW prototype was built in the laboratory and preliminary experimental results were obtained.