[雙語翻譯]--（節(jié)選）外文翻譯--電力應(yīng)用領(lǐng)域中的燃料電池功率調(diào)節(jié)概要（原文）

1、Fuel cell power conditioning for electric power applications: a summaryX. Yu, M.R. Starke, L.M. Tolbert and B. OzpineciAbstract: Fuel cells are considered to be one of the most promising sources of distributed energy bec

2、ause of their high efficiency, low environmental impact and scalability. Unfortunately, multiple complications exist in fuel cell operation. Fuel cells cannot accept current in the reverse direction, do not perform well

3、with ripple current, have a low output voltage that varies with age and current, respond sluggishly to step changes in load and are limited in overload capabilities. For these reasons, power converters are often necessar

4、y to boost and regulate the voltage as a means to provide a stiff applicable DC power source. Furthermore, the addition of an inverter allows for the conversion of DC power to AC for an utility interface or for the appli

5、cation of an AC motor. To help motivate the use of power conditioning for the fuel cell, a brief introduction of the different types, applications and typical electrical characteristics of fuel cells is presented. This i

6、s followed by an examination of the various topologies of DC–DC boost converters and inverters used for power conditioning of fuel cells. Several architectures to aggregate multiple fuel cells for high-voltage/high-power

7、 applications are also reviewed.1 IntroductionFuel cells are environmentally sound renewable energy sources that are capable of operating at efficiencies greater than traditional energy production methods. Moreover, the

8、scalability of fuel cells has allowed for applications in almost every field, including distributed generation. However, some inherent obstacles exist in the application of fuel cells. Low output voltage that varies with

9、 age and current, reduced efficiency with output ripple current, slow response to a load step response, no overload capa- bility and no acceptance of reverse current provide many technical challenges that must be overcom

10、e by power- conditioning systems. In this paper, a discussion of the construction, types, application and electrical characteristics of fuel cells is pre- sented. This is followed by an examination of several differ- ent

11、 approaches to power-conditioning systems for single and multiple fuel cell combinations.1.1 Fuel cell constructionIn 1839, William Grove discovered that by combining oxygen and hydrogen in a particular configuration, el

12、ectri- city could be generated. Although this discovery was made more than 160 years ago, the basic operating principle discovered still applies. A basic schematic diagram of a fuel cell is shown in Fig. 1. Hydrogen is a

13、pplied to the anodewhere a catalyst separates the hydrogen into electrons and positive hydrogen ions. A membrane separating the anode and cathode allows the positive hydrogen ions to permeate through while rejecting the

14、electrons. This forces the elec- trons to take the provided electrical path, or circuit, to the cathode. Once the electrons reach the cathode, they recom- bine with the oxygen and hydrogen ions to form water. The followi

15、ng basic reactions demonstrate the process:Anode side: 2H2 ! 4Hþ þ 4e?Cathode side: O2 þ 4Hþ þ 4e? ! 2H2ONet reaction: 2H2 þ O2 ! 2H2OWhen pure hydrogen is used as the fuel, only electricity

16、 and water are generated from the fuel cell. This attributes the fuel cell as an environmentally friendly source of energy. To obtain pure hydrogen, a fuel processor or refor- mer is often implemented. A reformer uses fu

17、els such as natural gas, coal and biomass to generate hydrogen. The construction of an actual fuel cell for power gener- ation is composed of several components as seen in Fig. 2. The fundamental components are rectangul

18、ar or cylindrical tubes that contain the anode, cathode and mem- brane and perform the generation and recombination of electrons. To create a fuel cell stack, these tubes are bundled together in series and parallel combi

19、nations to produce units between a few kilowatts to a hundred kilo- watts. For utility applications where large-scale power is required, the fuel cell stacks can be amassed into tiers. These tiers can be assembled into s

20、ub-megawatt to mega- watt generator assemblies.1.2 Types of fuel cells and their applications[1–6]Since William Grove’s discovery, an assortment of fuel cells has been developed. The general classifications of# The Insti

21、tution of Engineering and Technology 2007doi:10.1049/iet-epa:20060386Paper first received 5th October 2006 and in revised form 19th January 2007X. Yu, M.R. Starke and L.M. Tolbert are with the Department of Electrical an

22、d Computer Engineering, The University of Tennessee, Knoxville TN 37996- 2100, USAB. Ozpineci is with the Power Electronics and Electric Machinery Research Center, Oak Ridge National Laboratory, Oak Ridge TN 37831-6472,

23、USAE-mail: tolbertlm@ornl.govIET Electr. Power Appl., 2007, 1, (5), pp. 643–656 643Concentration losses are a result of the inability of the surrounding material to maintain the initial concentration of the fuel. As the

24、reactant is consumed at the electrode, the concentration of the surrounding material reduces on account of the transportation rate of the reactants. This loss can be quite severe particularly at high current densities. A

25、long with the losses, the V–I polarisation curve of the fuel cell is also dependent on operating temperature. Figs. 3 and 4 show two different fuel cell curves with the temperatures of 40 and 8008C, respectively. For low

26、- temperature fuel cells, the open circuit voltage is lower than the ideal value, and a region of activation polarisation is present. Contrarily, the open circuit voltage for a high- temperature fuel cell is nearly ident

27、ical to the ideal value and almost no region of activation polarisation is acquired.2 Power electronics interface requirementsCurrently, no standard output voltage rating for fuel cells has been established. Most of the

28、present fuel cell stack modules produce an output voltage in the range 24–150 VDC. However, the large number of applications in which fuelcells can be implemented necessitates that a power elec- tronics interface be pres

29、ent. This interface should:? control the fuel cell voltage ? convert the fuel cell output to the appropriate type and magnitude ? deliver a high power factor (grid applications) ? provide little to no harmonics ? operate

30、 efficiently under all conditions and ? add little to the cost of the overall system.The power electronics interface for fuel cells often utilise DC–DC boost converters and inverters to boost the fuel cell voltage and co

31、nvert the DC voltage to AC as seen in Fig. 5. The expectations from the boost converter, in addition to boosting the fuel cell voltage, are regulation of the inverter input voltage and electrical isolation of the low- an

32、d high- voltage circuits. The inverter need only convert the DC to AC with reasonable harmonic elimination and can either be single, dual, or three phase depending on the application. Single- and dual-phase inverters are

33、 used for residential applications, whereas three-phase inverters are implemented in industrial applications and in centralised power generation. Another topology that is possible, but rarely capitalised, is that of Fig.

34、 6. This topology neglects the use of DC– DC converters and instead relies on a transformer at the output of the inverter to boost the voltage. The advantage in exercising a DC–DC converter over this topology is 2-fold:

35、size and cost. A transformer capable of boosting to a high voltage is significantly bulky and very costly. The following sections discuss the specific fuel cell restrictions and possible methods for power converters to c

36、ope with these requirements.2.1 No regeneration/reverse currentFuel cells, in general, cannot accept current. Therefore to obstruct current flow to the fuel cell, a diode DFC can be inserted in series with the fuel cell

37、module as seen inFig. 3 Cell voltage for a low-temperature air pressure fuel cell [2]Fig. 4 Voltage of an SOFC operating at about 800 8C [2]Fig. 5 Fuel cell power electronics interface block diagram for residential appli