hybd cell wordform

7/31/2019 Hybd Cell Wordform

1/5

Photovoltaic Fuel Cell Hybrid SystemImplemented by Matlab/ Simulink

Yogesh.P, Sendil.MPrathyusha Institute Of Technology And Management- Thrivallur

Anna [email protected] , [email protected]

Abstract:

This paper mainly deals with the Simulation of a gridconnected hybrid power system, referred to ashydrogen Photovoltaic -Fuel Cell (PVFC) hybrid

system. It couples a photovoltaic generator (PV),alkaline water electrolysis, a storage gas tank, aproton exchange membrane fuel cell (PEMFC),inverters and power conditioning units (PCU) to givedifferent system topologies. The system is intendedto be an environmentally friendly solution since ittries maximizing the use of a renewable energysource. Electricity is produced by a PV generator tomeet the requirements of a user load. Whenever thereis enough solar radiation, the user load can bepowered totally by the PV electricity. During periodsof low solar radiation, auxiliary electricity isrequired. the operational performance of the systemare component efficiency, system design andconsumption behavior. In this paper Photovoltaic fuelcell hybrid system has been concentrated in the ACgrid connected components and the hybrid systemhas been simulated by using Matlab.

INTRODUCTION

The conventional fossil fuel energy sources such aspetroleum, natural gas, and coal which meet most of the worlds energy demand today are being depletedrapidly. Also, their combustion products are causingglobal problems such as the greenhouse effect andpollution which are posing great danger for the

environment and eventually for the entire life on ourplane. The renewable energy sources (solar, fuel cell,wind, tidal, geothermal etc.) are attracting moreattention as an alternative energy. Among therenewable energy sources, the photovoltaic (PV)energy has been widely utilized in low powerapplications. It is also the most promising candidatefor research and development for large scale users asthe fabrication of low cost PV devices becomes a

reality. Photovoltaic generators which directlyconvert solar radiation into electricity have a lot of significant advantages such as being inexhaustibleand pollution free, silent, with no rotating parts, andwith size-independent electric conversion efficiency.

Due to harmless environmental effect of PVgenerators, they are replacing electricity generated byother polluting ways and even more popular forelectricity generator where none was availablebefore. With increasing penetration of solarphotovoltaic devices, various anti-pollution apparatuscan be operated by solar PV power. From anoperational point of view, a PV power generationexperiences large variations in its output power dueto intermittent weather conditions. Those phenomenamay cause operational problems at the power station,such as excessive frequency deviations. In manyregions of the world, the fluctuating nature of solarradiation means that purely PV power generators foron grid applications must be large and thusexpensive. One method to overcome this problem isto integrate the photovoltaic plant with other powersources such as diesel, fuel cell (FC), or battery back-up.The fuel cell back-up power supply is a veryattractive option to be used with an intermittentpower generation source like PV power because thefuel cell power system is characterized with betterefficiency, fast load-response, modular productionand fuel flexibility. Its feasibility in co-ordinationwith a PV system has been successfully realized forboth grid-connected and stand-alone power

applications. Due to the fast responding capability of the fuel cell power system, a photovoltaic-fuel cell(PVFC) hybrid system may be able to solve theinherent problem of intermittent power generation.Unlike a storage battery, which also represents anattractive back-up option, such as fast response,modular construction and flexibility, the fuel cellpower can produce electricity for unlimited time tosupport the PV power generator. Therefore, a
mailto:[email protected]:[email protected]:[email protected]


2/5

continuous supply of high quality power generatedfrom the PVFC hybrid system is possible day and

night.

PHOTOVOLTAIC-BATTERY-FUEL CELLHYBRID SYSTEM

The diesel generator in this system is replaced by afuel cell system. The proposed PVFC hybrid systemis shown in fig(1).The fuel cell system is used as aback-up generator, when the batteries reach theminimum allowable charging level and the loadexceeds the power produced by the PV generator.The advantages of this system are in general the sameas for a Photovoltaic-Fuel Cell hybrid system withregard to the PV generator size and Fuel cellavailability. Some principal differences exist betweena diesel generator and a fuel cell which affect thedesign, sizing and the operating strategy of such ahybrid system. For example, a diesel generator willprovide the rated power to the load in a few secondsafter start up, but a fuel cell system needs more timeto provide the rated power and the output should onlybe increased slowly after start up. The increasingoperating temperature which occurs during operationdoes improve the efficiency of a fuel cellsignificantly. According to the load profile, thefeasible fuel cell capacity can be determined, whereasa diesel generator should be operating at the ratedpower as much as possible. A significant advantageof the fuel cell as a Back-up generator over the dieselor petrol generator is the high conversion efficiencyof the fuel cell. Whereas a 1kW diesel generatorachieves total efficiencies between 8-15%, a similar

fuel cell system can achieve up to 50% efficiencywhen operated with H2 and O2. Diesel generatorsneed high maintenance costs and they are noisy andemit exhaust gases continuously. In contrast, the fuelcells have very good technical properties which makethem interesting for stand-alone power systems, suchas low noise level and clean exhaust gases, especiallywhen pure hydrogen is used as a fuel. Due to theirvery low maintenance cost, the fuel cells are expectedto generate electricity at lower cost than conventionaldiesel generators in spite of their higher initialinvestment cost. Lower investment cost and higherlife time of fuel cell systems are expected in the

future, when mass production and technicalimprovements are realized.For many applications, a loss of feeding loads is notacceptable. In order to achieve no loss of feedingload probabilities with a PV generator, the systemmust be designed according to the worst case climateand load conditions. Therefore, another source of energy is necessary to realize energy storage. In thissystem, the excess energy is stored in the form of compressed hydrogen via conversion through the

electrolyser. The fuel cell is used to produce power if the load power exceeds that produced from the PVgenerator. It can also function as an emergencygenerator, if the PV generator system fails. With atotal efficiency of the storage system in the range of 50%, a suitable storage volume can be achieved andthe PV generator capacity can be reducedsignificantly. This compensates partially the extracost of the hydrogen system. Based on the siteclimate, the load profile, the characteristic of thecomponents, and the storage volume can beoptimized. For many years, a number of hybridsystems have been realized using hydrogen forseasonal energy storage. Different system topologieshave been used. Most common is the DC connectionof PV generator, electrolyser, and fuel cell with, oreven without, a DC/DC converter. All these systemtopologies will be studied in details in this work.Technically, this system can possibly store not onlythe hydrogen but also the oxygen, but safety andeconomic point of view the oxygen storage is notpreferable.

AC COUPLED SYSTEM TOPOLOGY

All system components in this topology areconnected to the AC user load via the AC bus-bar,Fig 2. The AC coupled system topology has asuperior performance compared to the DC coupledconfiguration since each inverter can be synchronized

to its generator so that it can supply the loadindependently and simultaneously with otherinverters. This offers some flexibility for the energysources to meet the user load demand. In case of lowload demand, all the inverters of the generators andstorages are in standby mode operation except oneinverter, for example the PV generator inverter, tocover the load demand. However, during high loaddemands or peak times, some generators and storageunits or all are operated in parallel to cover the userload demand. Because of this parallel operationcapability, the capacities of the power conditioningunits (PCUs) and the generators are reduced. This

topology has several advantages compared to the DCcoupled topology such as higher overall efficiency,smaller sizes of the PCUs while keeping a high levelof energy availability, and optimal operation of thediesel generator The operation and control of thistopology are sophisticated due to the synchronizationprocess required between the components. due toreducing its operating time and consequently itsmaintenance cost.


3/5

Figure 1. Block diagram PVFC hybrid system

The development of an advanced PCU simplifies thecontrol and the load dispatch problem. Therefore,advanced control algorithms which build andstabilize the isolated grid and allow parallel operationof different renewable and conventional generators aswell as the integration of storage media have beendeveloped, Moreover, due to continuousimprovement in the power conditioning units, suchcomplicated control tasks become reliable in theirapplications. In this way, the expansion or

modification of the hybrid system configurations caneasily be carried out in order to cover the demandgrowth or change in demand behavior. Recentdevelopments allow coupling all components of a PVhybrid system on the AC side in a standardized way.Main features of this method are systemexpandability, general adaptability, utility-gridcompatibility, cost reduction, and simple systemdesign and installation.

SIMULINK MODEL


4/5

Simulation result

Figure 3: PV cell ac grid connection simulation result

Figure 4: Fuel cell ac grid connection simulation result


5/5

CONCLUSION

Hybridizations through combining different energysources in one supply system offer the bestpossibility to use locally available renewableenergies. The modular hybrid power system couplingall generators, storage media and user loads on theAC side come out with numerous advantages, such assimplicity in system design, high reliability, andexpandability. The nature of hybridization is mainlybased on the special features and economic potentialof various energy conversion processes and on thepower range. Moreover, the AC side structureprovides standardization, quality assurance and serialproduction which also results in a considerablepotential of cost reduction. Hybrid PVFC systemhaving high efficiency compared to other hybridsystem and typical waveforms obtained throughnumerical simulation using Matlab/Simulink. Infocusing to the future hybrid system like this withcombination of PVFC system or any other

combination will be feasible solution for betterregulation.

REFERENCE

(1) A Forrai, "Fuel-Cell Parameter Estimation andDiagnostics," Energy Conversion, IEEE Transactionon, vol. 20, pp. 668-675, 2005(2) M. U. Iftikhar, D. Riu, F. Druart, S. Rosini,YBultel and N. Retire, "Dynamic modeling of proton exchange membrane fuel cell using non-integer derivatives," Journal of Power Sources, vol.160, pp. 1170-1182, 10/6. 2006.(3) M. A. A. Younis, N. A. Rahim and S. Mekhilef,"Fuel cell model for three-phase inverter," in 2006,pp. 399-404.(4) S. Pasricha and S. R. Shaw, "A dynamic PEMfuel cell model," Energy Conversion, IEEETransaction on, vol. 21, pp. 484-490, 2006.(5) Caisheng Wang, "Fuel cells and load transients,"Power and Energy Magazine, IEEE, vol. 5, pp. 58-63, 2007

hybd cell wordform

Documents