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Transcript
“PROPOSED PHILIPPINE NATIONAL STANDARDS
FOR RENEWABLE ENERGY TECHNOLOGIES”
SOLAR PV SYSTEM COMPONENTS
INVERTERS FOR STAND-ALONE PHOTOVOLTAIC
APPLICATIONS
GENERAL SAFETY AND
PERFORMANCE REQUIREMENTS
DESIGN QUALIFICATION AND
TYPE APPROVAL
JUNE 2006
INTRODUCTION
This proposed standard covers general, safety and requirements for non-utility interactive
sinewave inverters used in photovoltaic systems. Performance requirements for these
inverters are also included.
Note: Safety requirements ensure that electrical equipment constructed in accordance with
these standards does not endanger the safety of person or property when properly installed,
maintained, and used in applications for which it was intended.
SECTION ONE - GENERAL REQUIREMENTS
1. SCOPE
This standard specifies general and safety requirements for non-utility interactive
sinewave inverter for small photovoltaic systems particularly for those with rated input
voltages of 12 Vdc and 24 Vdc.
2. DEFINITIONS
2.1.
Rated voltage range: Range of dc voltage over which the inverter is intended to
be operated.
2.2.
Design voltage: Voltage declared by the manufacturer to which all the inverter
characteristics are related.
2.3.
Live part: Conductive part which may cause an electric shock in normal use. The
neutral conductor shall, however, be regarded as a live part.
2.4.
Type test: Test or series of tests made on a type-test sample for checking
compliance of the design of a given product with the requirements of the
relevant specifications.
2.5.
Type test sample: Sample which consists of one or more similar units submitted
by the manufacturer or responsible vendor for the purpose of a type test.
3. GENERAL REQUIREMENTS
Inverters should be designed and constructed such that in normal use they do not cause
danger to the users and surroundings.
In general, compliance for inverters is checked by carrying out all the tests specified and
described in Section 3 (Standard Test Methods) of the Inverters for Stand-alone
Photovoltaic Applications – Design Qualification and Type Approval.
4. GENERAL NOTES ON TESTS
4.1.
Tests according to this standard are type tests.
-1-
Note: The requirement and tolerances permitted by this standard are related to
the testing of a type-test sample submitted for that purpose. Compliance
of the type test sample does not ensure compliance of the whole
production of a manufacturer with this safety standard.
4.2.
Unless otherwise specified, the tests are carried out at room temperature
between 20°C and 40°C.
4.3.
It is permissible to substitute a battery by a dc power source provided that the
source impedance is equivalent to that of a battery.
4.4.
Three samples are required for testing. In such cases, if more than one inverter
fails, the type sample is rejected.
4.5.
If one inverter fails, the test is repeated using the other two inverters and both
should comply with the test requirements.
5. MARKINGS
5.1.
Inverters should be clearly marked with the following mandatory markings:











5.2.
Mark of origin (trade mark, manufacturer's name or name of the responsible
supplier),
Model number or type reference of the manufacturer,
Rated input battery voltage,
Rated output ac voltage,
Rated output frequency,
Rated power output,
Peak power rating,
Continuous power rating,
Intermittent power rating,
Rated voltage output wave form,
Note or mark indicating whether the inverter is proof against supply voltage
polarity reversals.
Markings shall be durable and legible.
Compliance is checked by inspection and by trying to remove the markings by
rubbing lightly for 15 seconds with two pieces of cloth: one soaked in water and
the other in petroleum spirit.
Note: The petroleum spirit should consist of a solvent hexane with a maximum
of 0.1 volume percentage aromatics content, a kauri-butanol value of 29, an
initial boiling-point of approximately 65°C, a dry-point of approximately 69°C
and a density of approximately 0.68 g/cm3.
5.3.
Inverter enclosure
Inverter enclosure should be able to sufficiently protect the inverter from the
ingress of water spray, dust and small insects.
-2-
5.4.
Inverter packaging
Light emitting diodes (LED) or liquid crystal display (LCD) should be present in the
front panel of the inverter to indicate voltage conditions of the battery. Optionally,
voltmeters and current meters may be added in the front panel. Furthermore,
audio or visual alarms may be incorporated in the inverter to warn users of
nearing load disconnection.
SECTION TWO - SAFETY REQUIREMENTS
6. TERMINALS
6.1.
Terminals should permit the connection of conductors from each component.
6.2.
Terminals should be prominently marked for polarities for each component in the
PV system.
7. CONSTRUCTIONAL REQUIREMENTS
7.1.
Inverters should be mechanically robust and should be designed such that they
minimize the effects of moisture and temperature during use as well as prevent
the ingress of insects, dust and water spray.
7.2.
Adequately robust means of fixing should be provided.
7.3.
Inverters must be easily serviceable.
8. PROTECTION AGAINST ACCIDENTAL CONTACT WITH LIVE PARTS
8.1.
Inverters should, when installed in normal use, be sufficiently protected against
accidental contact with live parts as.
Lacquer and enamel are not deemed to be adequate protection or insulation for
the purpose of this requirement.
8.2.
Parts providing protection against accidental contact should have adequate
mechanical strength and should not loosen in normal use. It must not be
possible to remove them without the aid of a tool.
Compliance is checked by inspection.
9. MOISTURE RESISTANCE AND INSULATION
9.1.
The inverter should be moisture resistant. It should not show any appreciable
damage after being subjected to the following test:
The inverter is conditioned for 48 hours in an enclosure with relative humidity
maintained between 91% and 95%. The temperature of the air at all places
where samples are located is maintained within 1oC of about 40°C.
-3-
9.2.
Insulation should be adequate between the input terminals bonded together
and all exposed metal parts.
Before the insulation test, remove visible drops of water, if any, with a blotting
paper.
The insulation resistance should not be less than 2 Mohm.
SECTION THREE - PERFORMANCE REQUIREMENTS
10. ELECTRICAL CHARACTERISTICS
Electrical characteristics of the inverter should be faithful to the manufacturer's data and
should be tested according to the procedures described in Inverters for Stand-alone
Photovoltaic Applications – Design Qualification and Type Approval.
The inverter must be tested for the following:
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
Stand-by power loss
Operating voltage range
Conversion efficiency
DC ripple
Power factor
Voltage and frequency variation
Total Harmonic Distortion
Electromagnetic noise
Acoustic noise
Ground path continuity
11. INVERTER PROTECTION
The provisions on Inverters for Stand-alone Photovoltaic Applications – Design
Qualification and Type Approval – Section One – Item 4 (Markings) apply together with
the following mandatory marking requirement:
11.1.
Indication of type and current rating of the fuse or disconnecting means, if
applicable.
11.2.
Resettable circuit breakers are acceptable as over current devices provided
they are rated for their intended use.
11.3.
Polarity reversal
To check if the inverter is proof against supply voltage polarity reversals,
operate it with reverse voltage for about 5 minutes at its maximum voltage
range. At the end of this period, the supply should be re-connected correctly
and the inverter should operate normally.
11.4.
Over-voltage/under-voltage. The inverter should be protected from lightning
flashes and inductive over-voltage as well as input under-voltage conditions if
applicable.
-4-
11.5.
In circuits where no transients are anticipated, fast acting fuses can be used.
11.6.
The inverter should be subjected to environmental and electrical cycling tests
described in the Inverters for Stand-alone Photovoltaic Applications – Design
Qualification and Type Approval – Section Two – Item 20 (Temperature Cycling
and Endurance Test) to determine potential failures. At the end of these tests,
the inverter should operate normally.
-5-
INVERTERS FOR STAND-ALONE PHOTOVOLTAIC APPLICATIONS
DESIGN QUALIFICATION AND TYPE APPROVAL
INTRODUCTION
This standard covers the requirements for the design qualification and type approval of
stand-alone sinewave inverters used in photovoltaic systems.
SECTION ONE - GENERAL REQUIREMENTS
1. SCOPE
This standard lays down the requirements for the design qualification and type approval
of stand-alone sinewave inverters used in photovoltaic systems suitable for long-term
operations.
2. PURPOSE
To determine the electrical and thermal characteristics of inverters. The actual life
expectancy of inverters, so qualified, will depend on their design, their environment and
the conditions under which they are operated.
3. SAMPLING
Three inverters for qualification testing (plus spares as desired) will be taken at random
from a production batch or batches. The inverters should have been subjected to the
manufacturer's normal inspection, quality control and production acceptance
procedures. The inverters should be complete in every detail and must be accompanied
by the manufacturer's handling, mounting and connection instructions, including the
maximum permissible voltage.
When the inverters are prototypes of a new design and not from production, the fact
should be noted in the test report.
4. MARKING
Each inverter should carry the following clear indelible markings:










Name, monogram or symbol of manufacturer
Type or model number
Serial number
Polarity of terminals
Output voltage
Nominal system voltage
Rated power
Peak power rating
Continuous power rating
Intermittent power rating
-6-

Voltage/current wave form
The date and place of manufacture should be marked on the inverter traceable from the
serial number.
5. TESTING
The inverter should be subjected to the test sequences detailed in Section 2 of the
Inverters for Stand-alone Photovoltaic Applications – Design Qualification and Type
Approval.
In carrying out the tests the manufacturers’ handling, mounting and connection
instructions must be strictly observed.
6. PASS CRITERIA
An inverter will be considered to have passed the qualification tests, if each test sample
meets the following criteria:
6.1.
No apparent damage appears on the inverter after the tests, conditions and
functions normally.
6.2.
No sample exhibited any short-circuit or open, circuit conditions during the tests.
6.3.
There is no visual evidence of a major defect, as defined in Section One - Item 7
(Major Visual Defects).
6.4.
The insulation test requirements are met after the tests.
Should the first sample fail any test, the other two inverters must be subjected to
all relevant tests, following the same sequence. If one or both of the inverters
fail, the design will be considered as not meeting the qualification standard. If,
however, both inverters pass the test sequence, the design will be considered as
successfully meeting the qualification requirements.
7. MAJOR VISUAL DEFECTS
For the purposes of design qualification and type approval, the following are considered
to be major visual defects:



shorted terminals
shorted routes in the printed circuit board
shorted electronic parts in the printed circuit board
8. REPORT
A certified test report of the qualification tests, with the measured performance
characteristics and details of any failures and re-tests should be prepared by the test
agency. A copy of this report must be provided to the manufacturers and be kept for
reference purposes.
-7-
9. MODIFICATIONS
Any change in the design, materials, components or processing of the inverter may
require a repetition of some or all the qualification tests to maintain type approval.
SECTION TWO - STANDARD TEST METHODS
10. GENERAL REQUIREMENTS
Tests are type test. One inverter will be subjected to all tests.
10.1.
Ambient temperatures
Tests should be made in a draught free room and at an ambient temperature
of about 20 to 40°C.
10.2.
Supply voltage
Unless otherwise specified the inverter to be tested must be operated at its
design voltage.
10.3.
Inverter stability
a. An inverter should be brought to a condition of stable operation before
carrying out measurements.
b. The characteristics of an inverter should be checked immediately before
and immediately after each series of tests.
10.4.
Instrument characteristics
10.4.1.
Potential circuit
Potential circuits of instruments connected across the inverter must
not pass more than 3% of the nominal running current.
10.4.2.
Current circuit
Instruments connected in series with the inverter should have
sufficiently low impedance such that the voltage drop will not
exceed 2% of the inverter voltage.
10.4.3.
R.M.S. measurements
Instruments should be essentially free from errors due to wave form
distortion and should be suitable for the operating frequencies.
10.4.4.
Inverter power source
It is permissible to substitute a battery by a D.C. power source,
provided that the source impedance is equivalent to that of a
battery.
-8-
11. MEASUREMENT OF STAND-BY POWER
Figure 1 gives a typical testing circuit. If this circuit is used, no correction is necessary for
the current drawn by the voltmeter, provided that the resistance of the voltmeter
complies with the requirements of item 10.4.1. Stand-by power should not exceed 1% of
rated power.
12. DETERMINATION OF OPERATING VOLTAGE
Figure 2 gives a typical circuit for the determination of operating voltage.
13. MEASUREMENT OF CONVERSION EFFICIENCY
The inverter efficiency must not be less than 90% at full load. Figure 3 gives a typical
circuit for the determination of inverter efficiency.
14. MEASUREMENT OF D.C. RIPPLE
There should be no ripple on the D.C. supply side of the inverter
Figure 4 gives the circuit for measurement of D.C. ripple.
15. VOLTAGE AND FREQUENCY VARIATION
The voltage regulation of the inverter should be less than or equal to 5% of the rated
output voltage while the frequency variation of the inverter should be less than or equal
to 1% of the rated output frequency.
16. TOTAL HARMONIC DISTORTION
The total harmonic distortion (THD) of the inverter should be less than or equal to 5%
with linear loads.
17. ELECTROMAGNETIC COMPATIBILITY
Electromagnetic compatibility must be lower than 40 dB at a distance of 10m.
18. ACOUSTIC NOISE
When operating over the rated voltage range and with load connected the inverter must
comply with the following requirements:


at and above an operating frequency of 18 kHz: no requirements;
below an operating frequency of 18 kHz: requirements under consideration.
-9-
19. ELECTRIC SHOCK CONDUCTIVITY TEST
In order to determine whether a conductive part is a live part which may cause an
electric shock, the inverter is operated at rated voltage and the following tests are
conducted:
19.1.
The current flowing between the parts connected and earth is measured, the
measuring instrument having a non-inductive resistance of 2000 ± 50 ohms. The
part concerned is a live part if a current of more than 0.7 mA (peak) or 2 mAdc is
measured.
19.2.
The voltage between the part concerned and any accessible part is measured,
the measuring instrument having a non-inductive resistance of 50,000 ohms.
The part concerned is a live part if a voltage or more than 34V (peak) is
measured.
For the above test, one pole of the test supply should be at earth potential.
20. TEMPERATURE CYCLING AND ENDURANCE TEST
Compliance is checked using the following tests:
The inverter should be mounted in accordance with the manufacturer's instructions,
operated in association with full load conditions at the maximum voltage of the rated
load and subjected to a temperature cycling test and an endurance test, as follows:
20.1.
The temperature cycling test will be carried out first at the lower limit of the
ambient temperature range for 1 hour. The temperature will be raised to the
upper limit of the ambient temperature range for 1 hour. Five such temperature
cycles are carried out.
20.2.
The endurance test should be carried out at the ambient temperature for the
following test period:
20.3.

for continual operation inverters: 200 h;

for intermittent operation inverters: 50 h.
At the end of this time, and after cooling to room temperature, the inverter
should operate the load at the rated voltage.
- 10 -
APPENDIX A - TEST CIRCUITS
INVERTER
A
+
D
C
S
U
P
P
L
Y
V
-
Figure 1. Circuit for Measurement of standby power loss
AC OUTPUT
V
220 V
INVERTER
A
+
VARIABLE
DC
SUPPLY
V
Figure 2. Circuit for measurement of inverter operating voltage
- 11 -
LOAD
A
V
INVERTER
A
+
DC SUPPLY
V
-
Figure 3.
Circuit for measurement of conversion efficiency
+
A
INVERTER
D.C. SUPPLY
-
SHUNT
WAVE ANALYZER/
OSCILLOSCOPE
Figure 4.
Circuit for measurement of D.C. ripple
- 12 -