A Compact Digitally Controlled Fuel Cell/Battery Hybrid Power Source

Dept. of Electr. Eng., Univ. of South Carolina, Columbia, SC
IEEE Transactions on Industrial Electronics (Impact Factor: 6.5). 07/2006; 53(4):1094 - 1104. DOI: 10.1109/TIE.2006.878324
Source: IEEE Xplore


A compact digitally controlled fuel cell/battery hybrid power source is presented in this paper. The hybrid power source composed of fuel cells and batteries provides a much higher peak power than each component alone while preserving high energy density, which is important and desirable for many modern electronic devices, through an appropriately controlled dc/dc power converter that handles the power flow shared by the fuel cell and the battery. Rather than being controlled to serve only as a voltage or current regulator, the power converter is regulated to balance the power flow to satisfy the load requirements while ensuring the various limitations of electrochemical components such as battery overcharge, fuel cell current limit (FCCL), etc. Digital technology is applied in the control of power electronics due to many advantages over analog technology such as programmability, less susceptibility to environmental variations, and low parts count. The user can set the FCCL, battery current limit, and battery voltage limit in the digital controller. A control algorithm that is suitable for regulating the multiple variables in the hybrid system is described by using a state-machine-based model; the issues about embedded control implementation are addressed; and the large-signal behavior of the hybrid system is analyzed on a voltage-current plane. The hybrid power source is then tested through simulation and validated on real hardware. This paper also discusses some important issues of the hybrid power source, such as operation under complex load profiles, power enhancement, and optimization of the hybrid system. The design presented here can not only be scaled to larger or smaller power capacities for a variety of applications but also be used for many other hybrid power sources

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    • "This also leads to a cleaner transportation system. A fuel cell–based power unit consists of a fuel cell, an energy storage device, and power electronic converters [5], [6]. The fuel cell is slow and can only provides constant power to support the average load demand. "
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    ABSTRACT: Fuel cell–based power units have increasingly become an attractive option to provide clean and efficient electricity in certain niche applications. This paper discusses the characteristics of a proton exchange membrane (PEM) fuel cell for a battery extender auxiliary power unit and explains the steps of the design process. A two-leg converter topology is proposed to control the fuel cell output, battery charge and discharge process, and the voltage of the DC link. Different operating modes of the system are analyzed and the functions of energy management system are studied. Sizing for the fuel cell, battery, power electronic converter, and passive components are presented, and the controllers of the power electronic converter are designed. Simulation case studies in both steady state and transient conditions are presented to validate the effectiveness of the presented fuel cell-based battery extender power unit and the proposed design process.
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    • "However, the various studies on fuel cell and battery hybridization have been offered enough understanding of efficient power and energy sharing but most of the studies did not propose a general analysis and design methodology in context to the intrinsic properties of each devices, such as the electrochemical reaction in the fuel cell and operating condition of the battery. Dougal et al. [16] [17] studied hybridization using a graphical approach. Their research on the hybrid system included fundamental and systematic studies. "
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    ABSTRACT: Hybridization is a promising method for enhancing the quality of the power supplying system including fuel cells which is not capable of meeting load demand statically or dynamically. Though there have been much research advances on hybridization, systematic studies are insufficient to reveal fundamental characteristics. In this study, we systematically categorize passive hybrid topologies, which are battery state of charge (SoC) controlled, fuel cell relative humidity (RH) controlled, and battery-fuel cell controlled, respectively. Each hybrid topology can be analyzed based on the graphical and mathematical method for fundamentally understanding and designing the hybrid system. First, in the graphical method, I-V curves, which represent the characteristics of the intrinsic properties of each device, are used for the understanding of the current sharing and power sharing of the hybrid system. Second, the mathematical method based on the relations deduced from each characterization curve is used for a more detailed understanding on topology to find key factors of hybridization. The results show that the power sharing of hybridization is strongly connected to the fundamental properties of each device, and it can be expressed by a combination of two factors K-V and K-R, which represent the electrical potential and internal resistance ratio of each device, respectively.
    Full-text · Article · Feb 2014 · Applied Energy
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    • "2. 시스템 구조 연료전지 시스템에서는, 연료전지의 느린 동특성을 보 상하기 위해 주로 배터리가 보조 에너지원으로 사용된 다. 표 1의 사양을 만족시켜주는 최적의 시스템 구조를 선정하기 위해 다양한 연료전지-배터리 하이브리드 시 스템 구조들을 비교분석해보자. 그림 1에서, 구조 1은 배터리팩이 부하에 직접 연결되 는 구조로써, 부하가 갑자기 변해도 출력전압이 거의 흔 들리지 않는 장점을 가지고 있다 [4] "
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    ABSTRACT: Existing energy sources convert chemical energy into mechanical energy, while fuel cell directly generates electricity through an electrochemical reaction between hydrogen and oxygen. Therefore, it has a lot of strong points such as high efficiency, zero emission, and etc. In addition, with the development of hydrogen preservation technique, some companies have been researching and releasing portable fuel cell power packs for specific applications like military equipment, automobile, and so on. However, there are some drawbacks to the fuel cell, high cost and slow dynamic response. In order to compensate these weak points, auxiliary energy storages could be applied to the fuel cell system. In this paper, the optimum structure for a 150W portable fuel cell power pack with a battery pack is selected considering the specification of the system, and the design process of main parts is described in detail. Here, main objectives are compact size, simple control, high efficiency, and low cost. Then, an automatic mode change algorithm, which converts the operating mode depending on the states of fuel cell stack, battery pack, and load, is introduced. Finally, performance of the designed prototype using the automatic mode change control is verified through experiments.
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