The Solar Hybrid Inverter i.e. Solar Inverter plus the Charge Controller is a prominent and revolutionary part of the newly added Solar Power Packs (AC Model – I,II,III) to the Solar Photovoltaic Testing standard of the Ministry of New and Renewable Energy (MNRE) for OFF-grid solar application scheme, 2016-2017. This paper presents the procedures and subjective analysis of the measurements carried out on the hybrid solar inverter as well as the solar system which includes the inverter on different parameters such as Total Harmonic Distortion (THD), Battery Low-Voltage Cut-off, Load Reconnect, Overcharge Cut-off, Electronic Efficiency etc. Apart from the protection parameters and the inverter efficiency test a study of the Battery Capacity (100% Capacity & Depth of Discharge (DOD)) which powers the inverter has been done. A brief discussion on battery capacity testing techniques has been provided to conclude the paper.

1. LUMINESCENCE 2017
Presentation on
“Test Operation Procedures for Electrical and Electronic Parameters of
Solar Photovoltaic Power Packs as per MNRE Specifications”
NATIONAL STUDENT CONGRESS ON ILLUMINATION
Technical paper presented by:
AkashBiswas
Opto-Electronics &Solar PV Systems Test &Calibration Lab
Electronics Regional Test Laboratory (East), Kolkata
Jadavpur University, SISED, Kolkata, India
a.biswasertle@gmail.com
Pickon Majumdar
School of IlluminationScience Engineering&Design
(SISED)
Jadavpur University
Kolkata, India
majumdarpikon@gmail.com

2. Whom does this paper cater ?
• Thispaper can be identified as anInformative paper or a test oriented
approach to provide customers from the Solar Industry to review and
get informed about the test operating procedures thatare conducted
over the samples they provide to receive an MNRE Certification.
• Thispaper also serves the needs of various test laboratories who are
willing to setup facilitiesto perform the MNRE 2016-17 for their
customer pool.

3. WHAT IS A SOLAR HYBRID INVERTER ?
• ThemosteconomicalhybridsolarInverteristheall-in-oneinverterwhich
containsa solarinverter andbatteryinverter/charger together withclever
controlswhichcanbeprogrammedtodeterminethemostefficientuseof
youravailableenergy.
• An all-in-onehybridsolar systemisbasicallya hybridinvertertogetherwith
a lithiumbatteryinonecompletepackage usuallyaboutthesamesizeofa
fridge.Howeverlikemostappliancesthereare manyfeaturesand
capabilitieswhichdifferentiatethewidevarietyofsystemsavailable.

4. • Theycan also be used for providing emergencybackup power whenthe electric
company's power fails. Inverterswith the built-in AC chargeroption, known as
Inverter/Chargers, allow you to connect a generator up to your off grid system
and automatically chargeupyour batteries when the solar power is getting too
low.

5. TEST OPERATING PARAMETERS AS PER
MNRE 2016-2017 TO BE PRESENTED
 ElectronicEfficiency
 TotalHarmonicDistortion(THD)
 Battery Low-VoltageCut-off
 LoadReconnect,
 OverchargeCut-off,
 DepthofDischarge(DOD)
 Shortcircuitprotection
 Battery reverse polarity
 ReverseflowofcurrentthroughPV Module
 Voltagedropbetweenbatteryandmoduleterminals
 Idlecurrent
 Capacitytestfor Solarbatteries.

6. WHAT IS “M N R E” ?
• MNRE or “Ministry of New & Renewable Energy” isa ministerial
establishment of the Government of India which thrives to promote the
culmination of “FREE” , “NEW” & “RENEWABLE” Energy production and
usage along with the traditional or rather Conventional forms of energy
production. MNRE is assisted by NISE for their Solar PV related
operations.

7. THEN WHAT DOES MNRE DICTATE ?
• MNRE has set the standards to test the different parameters for “OFF
GRID SOLAR APPLICATIONS SCHEME”
• Constant meetings and discussions are carried out regularly by the
ministry and Test Engineers of Laboratories across India to develop the
Test standards, Spec. limits and operating procedures to carry out
these tests.
• MNRE also helps budding Entrepreneurs and organisations with
financialfunding and projects to promote production and usage of
Non-Conventional Energy.

8. WHO ALL CONDUCT THESE TESTS AND
PROVIDE CERTIFICATION ?

9. WHAT IS A SOLAR OFF GRID SCHEME ?
DC
• SOLAR HOME LIGHTING SYSTEMS
• SOLAR LANTERNS
DC
• SOLAR STUDY LAMPS
• SOLAR STREET LIGHTING SYSTEMS
AC
• SOLAR POWER PACKS

10. WHAT IS A SOLAR POWER PACK ?
• A Solar Power Pack is nothing but a nomenclature subtended to a solar
lighting system which is also used to power the AC loads or electronic
household devices by converting the DC supply provided by the
battery conceived by the photovoltaic module to AC (230V-50Hz)
power with the help of a Hybrid Inverter.
P V
MODULE
SOLAR
INVERTER
BATTERY
Towards AC Load

11. TEST OPERATING PROCEDURES

12. Electronic Efficiency and THD of the
Solar Power Pack
• The electronic efficiencyof theAC SolarPowerPackdepends heavily uponthe variableAC load
.ConstantDCsupplyof24Vis provided tothe inverterinputwithvoltmeter in parallelandan
ammeterin series torecordthe inputpower.On theoutputterminalthe variableloadis preparedby
connecting oneor morerheostatsin series ofa maximumof3Aratingwith anammeterin series and
avoltmeter in parallelor a300Wincandescentbulbtoattainafull loadscenarioandoutputpower
factorof1 fora300VAinverter torecordthe outputpowerofthe PowerPack.Theformulafor
calculationis statedbelow:
WhereµstandsforElectronic Efficiencyofthe powerpack.
• As per MNREstandardthe spec.limit forelectronic efficiency shouldbe≥ 90%.
• The totalharmonicdistortionoftheoutputpowerfromthe inverteris analysedandrecordedwith
the help ofaPowerAnalyserconnectedatthe outputterminals.The spec.limit forTHD is≤5% asper
MNREstandards.

14. Low voltage cut-off and Load
reconnect
• Thelow voltage cut-off is the threshold of the lower side of the inputvoltage upto which the power pack should
provide continuous supply to the load connected. This cut-off limit is provided to protect the battery from
damage due to deep discharge. Wheneverthis ‘deep discharge’ occurs the battery capacity and health gets
reduced by small amounts and can get completely destroyed after repeated misuse. Thereforethe hybridsolar
invertershould havea built-inswitching system to restrict the furtheruse and the Low voltage cut-off test
confirms that by recording theinput voltage at load (hereluminary)switch-off while the variable DC source
voltage is lowered gradually.
• Theload reconnectvoltage is the voltage at which the solar hybridinverterreconnectsthe load with the battery
supply after the lower cut-off has been achieved. If thevoltage requiredto reconnect(the reconnecttime) is
significantly lower thenthe load mayswitch on and off veryrapidly and maycausesevere damage to theload
while on the other handif the reconnect voltage is too high thenthe load might take longertime to switch on
and might wait till the PV module fullyrechargesthe battery yetagain.

16. Over charge Cut-off
• The over charge voltage isthe limit to which the battery attainsfull
charge and can store no more energy. If the battery continues to gain
energy at full rate from the module the battery voltage gets too high
which might lead to battery overheating and loss of electrolyte.
Therefore the cut-off to over charge of the battery is required once it
attainsthe higher cut-off voltage. Thismeasurement is done by
identifying the voltage at the module terminal which is provided by a
variable DC power supply gradually and charging the battery viathe
hybrid inverter. Here the over charge cut-off voltage isrecorded once
the ammeter, connected in series to the module terminal indicates 0
Amp.

18. Short circuit protection

19. Battery Reverse Polarity Protection

20. Module Reverse Flow Protection
• Similarlyprotectionagainstmodulereverseflow ofcurrenttothebatteryorherein caseofinverter
shouldbeprovidedandis usuallydone byconnectinga blockingdiode acrossthemoduleterminal.
The belowdepicteddiagramshowsthe proceduretoconductthe test

21. Idle current
• The Idlecurrentis thecurrentwhichis requiredtodrive theinternalcircuitryofthe invertereven
when theload(luminary) isoffi.e thecurrentstill flowing outofthe batterytopowerthe active
devices like BJT, MOSFET,andSCRof theinverter.An ammeterin series tothe inverterattheinput
terminaldeterminesthe idlecurrentofthe inverterwhen loadis opencircuited.As per MNREthe
spec.limit ofthetest is≤150 mA .

22. Voltage Drop between Module &
Battery Terminals
• A voltage difference between battery and module terminals must be
there just to ensure the proper charging of the battery but to maintain
this we also need to ensure thatthe voltage drop between the module
and the battery terminals should be asless as possible. The connection
with a voltmeter from battery terminal to module terminal should be
done at both the positive and negative ends of the terminals as
depicted in the diagram. The MNRE specification for this test is≤ 1V
for the combined voltage drop between module and battery terminals.

24. TEST PROCEDURES OF THE BATTERY
OF THE SOLAR POWER PACKS
• The capacity tests are mainly charge/ discharge cycles which are
carried out at a particular hour rate or rather a constant current to
observe whether or not the battery hasthe ability to provide power or
energy for the mentioned time interval and also for the low voltage
cut-off point of the inverter/load. The test procedures are elaborately
described below.

25. 100% capacity at C/10 or suitable
discharge rate
• Capacity(Ah) is themost importantparameterforassessmentof abatteryforits capabilityto
supplyelectrical powerin respect oftimeanddemandofcurrentbythe load.
• The basisofthis testis designed onthe factthatthe batteryshouldbechargedanddischarged
accordinglywithaconstantcurrentformulatedoridentified fromtheir ‘C’ ratingwhichmight range
fromC10toC20 forsolarPVsystems.Forexampleabatteryof100Ahhaving aC10rating
representsthatthe batteryifchargedordischargedataconstantcurrentof10A (i.e. 100Ah 10C)
thenthe batterywould drainoutcompletely by10hrs.Thismeans thatthe C10ratingrepresentsa
batterydrainageata 10hourrate.Nowacapacitytesthas been notifiedbytheMNREtoverify the
abovementionedphenomenonat100%capacityofthebattery.

26. • Modern day laboratories use advancedinstruments like “The Automatic Battery
Tester” by BITRODE Corporation, USAwhich ease off the charge dischargecycle
while recording the time and in turn capacity with the help of the BITRODE
software and server. Theschematic diagram of the modern test setup is shown
below

27. % Capacity between fully charged and load cut off
condition
• Havinga spec.limitof75%mentionedbytheMNREthecapacitybetween
fullycharged andtheloadcutoffconditionvoltageor rather the“Depthof
Discharge”testiscarriedoutinthesameprocedureas ofthe100%capacity
testwithonlyoneexceptionthatthedischargeisdonewiththesame
constantcurrentbuttheendvoltagehereshouldbethe“LowVoltageCut-
off”valueofthevoltagerecordedduringtheinverter testuptowhichthe
batteryshouldbedischargedandthetimerecordedshouldnotbe<75%of
thehourrate ofthebatteryi.e.for a100Ah batteryat a C10dischargerate
thedischargetimetoreach thelower cut-offshouldbenotlessthan7 hours
and30 minutesforan example.

29. CONCLUSION
• The Solar Power Pack hasbecome the ultimate solution to the AC load
crisis to the Indian rural/sub-urban house hold. The solar hybrid
inverter which is anintegral part of the power pack plays a vital role in
the production of AC power off-grid and in this paper we have tried to
analyze the test methods and operating procedures formulated by the
MNRE and are of umpteen need of certification for the Indian Solar
market.

30. ACKNOWLEDGMENT
• This study was supported by Jadavpur University. We thank our colleagues from
Electronics Regional Test Laboratory (East), Kolkata who provided insight and expertise
that greatly assisted the study, although they might not agree with all of the conclusions
of this paper.
• We thank Mr. SukumarGoswami, Scientist ‘B’, ERTL(E) for assistance with the solar
battery test procedures and Mr. Dilip Roy, Scientist ‘C’ for electronic based test procedures
that greatly improved the manuscripts.
• Last but not the least we are also immensely great full to Prof. Suddhasatwa Chakroborty,
Assistant Professor, Jadavpur University & Technical Director, ISLE-CSC for his comments
on an earlier and the final version of the manuscript, although any errors are our own and
should not tarnish the reputations of these esteemed persons.