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Energies 2016,9, 240
Thissystemwastestedbyvaryingthecompressorspeed. Theconclusionsshowedthatboth the
heatingandthecoolingcapacitiesof thesystemincreasedwith theriseofcompressorspeed,whereas
theCOPs inbothcasesdecreased. Jabardo et al. [37]alsoreportedanautomotiveACsystemequipped
withavariablecapacitycompressor runbyanelectricmotorcontrolledbyafrequencyconverter. The
impactonsystemperformanceofoperationalparameterssuchascompressorspeed, returnair in the
evaporatorandcondensingair temperatures,wasexperimentallyevaluatedandsimulatedbymeans
of thedevelopedmodel. Tobetterdevelop the inverterACsystem, all factorswhich influence the
performanceof thevariable frequencyACsystemhavebeendiscussed in[38]. Effectsofcompressor
frequencyontheperformanceandparametersareshowninFigure2.Atafixedambient temperature
andheat transferareaofheatexchangers, thecoolingcapacityandpowerconsumption increasedas
thecompressor frequency increased. Incontract, theenergyefficiencyratio (EER) initially increased
butsubsequentlydecreased, so thecompressor frequencyshouldbe increased inorder to improve the
coolingcapacity,while it shouldbedecreasedinorder toreducepowerconsumption. Theseresults
areveryuseful foroptimizing thedesign,andautomaticallycontrollinganddiagnosingexceptions in
theoperationofvariable frequencyACsystems.
ȱ
Figure2.Effectsofcompressor frequencyontheperformanceandparameters [38].
Inadditiontovariable-speedcompressors,adjustingthefanspeedcanleadtofurtherperformance
andefficiency improvements. Lee et al. [39] focusedon the effect of outdoor coil fan speedon the
performancevariationof theheatpumpsystemadoptingthehotgasbypassmethod. The integrated
heating capacitywith hot gas bypasswas highest at 60% (780 rpm) fan speed. This valuewas
4.4%higher than thatof the constant speed fan. On theotherhand, theaveragedCOPof theheat
pump in this casewas higher by 2.8% than the constant speed fan. Asmentioned in [40], three
frequency converterswere equipped to control the speedsof the compressor, the evaporator fans
and thecondenser fans, respectively. Theanalysis showedthat the three speedscouldbeadjusted
simultaneouslyaccordingtobothactualworkingconditionsandoperationmodesothattheACsystem
couldoperate inanoptimumstate,but inpracticalapplicationsonlyonefanspeedandcompressor
speedneedtobemodulated inreal-time,consideringhardwarecostsandsystemcomplexity.
Advancedcontrolalgorithmshavealsobeenstudiedbymanyauthors. Yeh et al. [41]proposed
twocontrolalgorithms. Thefirstalgorithm,whichmodulatedtheoutdoor fanspeed,couldenhance
thesteady-statepowerefficiency. Thesecondalgorithm,whichaddedonemoredegreeof freedomto
controlbymodulating the indoor fanspeed,could improvethe transient response. Theperformance
of theACsystemcouldbe improvedifbothalgorithmsweresimultaneously implemented in theway
that thesecondalgorithmwasresponsible for thecontrolactionduringthestartup/transientphase
ofoperation, andthefirstalgorithmtookoverat steadystate. Shi et al. [42]described threecontrol
algorithms for the inverterACsystem: thematrix control, the system-relative commands control
and the fuzzy control. Moreover, to realize comfort and systemenergy efficiency, they explained
themechanismtoregulate the runningspeedof thecompressor, indoorandoutdoor fans, and the
openingof theexpansionvalve.AsshowninFigure3,anartificialneuralnetwork-basedcontroller
348
Emerging Technologies for Electric and Hybrid Vehicles
- Title
- Emerging Technologies for Electric and Hybrid Vehicles
- Editor
- MDPI
- Location
- Basel
- Date
- 2017
- Language
- English
- License
- CC BY-NC-ND 4.0
- ISBN
- 978-3-03897-191-7
- Size
- 17.0 x 24.4 cm
- Pages
- 376
- Keywords
- electric vehicle, plug-in hybrid electric vehicle (PHEV), energy sources, energy management strategy, energy-storage system, charging technologies, control algorithms, battery, operating scenario, wireless power transfer (WPT)
- Category
- Technik