A Hybrid Fuel Cell Power System

Abstract

This paper proposes a hybrid fuel cell power system, which consists of a fuel cell, an isolated unidirectional converter, a bidirectional converter, an inverter, and a battery. The fuel cell and the battery are connected to the same voltage bus through an appropriate hybrid full-bridge LLC resonant unidirectional converter and a three-level buck/boost bidirectional converter, respectively. The battery is an auxiliary energy source, powers the load during the system's start state to make it easy for the system to cold start, and provides or absorbs the dynamic power when the load varies and the fuel cell cannot respond immediately, so the system dynamic characteristics are improved. Furthermore, the battery can also provide peak power at overload, so the power rating of the fuel cell can be decreased, which reduces the total system cost. In order to ensure that the system operates with high efficiency, this paper also proposes a power management control scheme, which controls the bidirectional converter operating under buck, boost, or shutdown mode according to the operation condition of the fuel cell and battery, so that the battery can be charged or discharged. The operation of the system during cold start and overload are analyzed in detail. A 1-kW fuel cell power system was built in the laboratory. Experimental results are shown to verify the theoretical analysis.

Effect of Load Priority Modeling on the Size of Fuel Cell as an Emergency Power Unit in a More-Electric Aircraft

“…Hybridizing the fuel cells with supercapacitors or batteries as the energy storage systems (ESS) can improve their performance and efficiency [10]. The feasibility of using fuel cells as the emergency power unit of aircraft has been considered in many research studies [1], and [11][12][13][14][15]. Therefore, the replacement of the emergency power unit based on the conventional generation system like ram air turbine by the hybrid fuel cell system is a proper solution to get closer to the advancement of electric aircraft [16].…”

Research on Composite Control Strategy of Quasi-Z-Source DC–DC Converter for Fuel Cell Vehicles

“…The average value of the output variable is y = u o . In the small-signal modeling method, each average variable is composed of a DC component and an AC small-signal component, as shown in Equation (18).…”

“…According to Equations (17) and (18) and ignoring the second order infinitesimal terms, the small-signal model of the converter can be written as Equation (19).…”

“…The high frequency pulsating voltage appears between the input and output and easily causes safety problems and electromagnetic interference problems. The converter proposed in [18] has low voltage stress, but the topology has a flying capacitor, which increases the difficulty of control. The multi-level converters are proposed in [19][20][21] to achieve high gain.…”

Isolated bidirectional DC-DC converter for supercapacitor applications

“…However since fuel cell stack has a slow response, using an auxiliary energy storage device such as battery or supercapacitor (SC) is recommended in the fuel cell (FC) applications [1][2][3]. While the battery has a large energy density and SC has a high power density, FC-Battery hybrid and FC-SC hybrid systems offer different features.…”