Technical Specification of Grid Connected-PV Inverter

CGC

Certification Specification of China General Certification Center CGC/GF004：2011 (CNCA/CTS 0004-2009A)

Technical Specification of Grid-connected PV inverter

2011-08-22 Publish

2012-08-22 Implement

China General Certification Center

Published

CGC/GF004:2011(CNCA/CTS 0004-2009A)

Contents Contents ........................................................................................................................................... 1 FOREWORD................................................................................................................................... 0 Technical Specification of Grid-connected PV inverter............................................................... 1 1 Scope................................................................................................................................... 1 2 Normative references ........................................................................................................ 1 3 Terms and definitions ....................................................................................................... 2 3.1 photovoltaic grid-connected inverter.................................................................... 2 3.2 photovoltaic array simulator ................................................................................. 2 3.3 inverter AC output terminal .................................................................................. 2 3.4 maximum power point tracking .......................................................................... 2 3.5 Maximum powder point tracking efficiency ........................................................ 3 3.6 conversion efficiency, energetic (ηconv) ............................................................... 3 3.7 overall(total) efficiency .......................................................................................... 3 3.8 islanding .................................................................................................................. 3 3.9 intentional islanding ............................................................................................... 3 3.10 unintentional islanding ........................................................................................ 3 3.11 anti-islanding ........................................................................................................ 3 3.12 simulated utility .................................................................................................... 4 3.13 quality factor, Qf .................................................................................................. 4 3.14 resonant frequency ............................................................................................... 4 3.15 temporary ............................................................................................................. 5 4 Product Categories .......................................................................................................... 5 4.1 Product type ............................................................................................................ 5 4.2 Output power Characteristics .................................................................................. 5 5 Technical requirements ..................................................................................................... 6 5.1 Use conditions ......................................................................................................... 6 5.2 Quality of the body and structure ......................................................................... 6 5.3 Performance indicators ......................................................................................... 7 5.4 Electromagnetic Compatibility .......................................................................... 9 5.5 Protection functions ............................................................................................. 11 5.6 Array insulation resistance detection ................................................................. 13 5.7 Array residual current detection ........................................................................ 14 5.8 Communication ................................................................................................. 15 5.9 Auto on / off ....................................................................................................... 16 5.10 Soft-start ............................................................................................................. 16 5.11 Insulation resistance and dielectric strength test ............................................. 16 5.12 Degrees of protection provided by enclosure ................................................... 16 5.13 Environmental test requirements ..................................................................... 17 5.14 Power control and voltage regulation ............................................................... 17 5.15 Continuous operation test..................................................................................... 17 5.16 Temperature rise test ......................................................................................... 17 6 Test methods .................................................................................................................... 19

CGC/GF004:2011(CNCA/CTS 0004-2009A) 6.1 Test environmental conditions............................................................................. 19 6.2 Inspecting the quality of main body and structure ........................................... 20 6.3 Performance index test ........................................................................................ 20 6.4 EMC test ............................................................................................................... 22 6.5 Protection functions tests ..................................................................................... 23 6.6 PV array insulation resistance test ........................................................................ 27 6.7 Residual current testing method ............................................................................ 27 6.8 Communication interface test ............................................................................. 28 6.9 Automatic power on/off test ................................................................................ 28 6.10 Soft start test ....................................................................................................... 28 6.11 Insulation voltage strength ................................................................................ 28 6.12 Degrees of protection provided by enclosure ................................................. 29 6.13 Environmental test ............................................................................................. 29 6.14 Power control and voltage adjustment test ...................................................... 29 6.15 Continuous operation test.................................................................................. 30 6.16 Temperature rise test ......................................................................................... 30 7 Inspection rules ............................................................................................................... 30 7.1 Inspection categories ............................................................................................... 30 7.2 Factory Inspection................................................................................................... 32 7.3 Type test ................................................................................................................... 32 8 Logo, Packaging, Transportation, Storage.................................................................. 32 8.1 Logo .......................................................................................................................... 32 8.2 Packaging ................................................................................................................. 33 8.3 Transport ................................................................................................................. 33 8.4 Storage ...................................................................................................................... 33 Appendix A .................................................................................................................................... 34 Table A: Technical parameter table of grid-connected PV inverter ...................................... 34 Appendix B .................................................................................................................................... 36 Select of anti-islanding protection scheme .................................................................................. 36 Appendix C .................................................................................................................................... 37 Transient Voltage Protection ........................................................................................................ 37 Annex D.......................................................................................................................................... 39 Inverter efficiency ......................................................................................................................... 39 Annex E .......................................................................................................................................... 41 Test conditions for dynamic MPPT efficiency ............................................................................ 41

FOREWORD To further guide our grid-connected photovoltaic inverter technology development, promote safe, efficient, reliable application and promotion of products and combine with the latest technical requirements of power, the original certification technical specification CNCA/CTS0004-2009 was amended. This technical specification is proposed by National Standardization Technical Committee 20 on Energy Fundamentals and Management. The technical specifications are presented and centralized by Beijing general Certification Center. The main drafting units of this technical specification are: Beijing general Certification Center, Sungrow Power Supply Co.,Ltd, State Grid Electric Power Research Institute, China Electric Power Research Institute, Institute of Electrical Engineering, Chinese Academy of Sciences, National Center Quality Supervision & Testing of Relay Protection and Automation Equipment, Beijing Corona Science&Technology Co.,Ltd, Beijing Nego Automation Technology Co.Ltd,, Zhuzhou CSR Times Electric Co.,Ltd. The main units involved in this technical specification are: SMA Solar Technology AG, KACO new energy GmbH, Siemens, Danfoss Drives A/S, Beijing Oasis New Energy Technology Co., Ltd., Fronius International GmbH, Beijing Jingyi Renewable Energy Engineering Co., Ltd, Beijing Soaring Electric Technology Co., Ltd, Beijing Rijia Power Supply Co., Ltd, Beijing Jike New Energy Technology Development Company, Suntech Power Holdings Co., Ltd, Shanghai Solar Energy Science & Technology Co., Ltd, Anhui Jiyuan Electric Power System Tech Co., Ltd, Sun Tech Solar Co., Ltd, Beijing Solar Power Institute, TBEA SunOasis Co., Ltd, Eifesun Sharing Green Energy, XJ Flexible Transmission System Corporation. The principal drafters of this technical specification are: Shilin Fan, Renxian Cao, Junjun Zhang, Wei Feng, Huaguang Yan, Nan Jiang, Hongchao Zhang, Geng Wang, Zong Wang, Lin Wan, Deliang Si, Taoyong Li, Yanxing Jiang, Tao Lei, Guichen Fu, Yun Li, Jie Liu, Wanyin Cai, Zhisen Zhang, Ta Meng, Yang Zhou, Mingfeng Yu, Jing Zhang, Wei Zhao, Youquan Zhang, Xiaoge Huang, Huo Wen.

CGC/GF004:2011(CNCA/CTS 0004-2009A)

Technical Specification of Grid-connected PV inverter 1

Scope

This technical specification provides product classification, terminology and definitions, technical requirements, test methods, inspection rules and signs, packaging, transportation and storage for grid-connected photovoltaic inverter. This technical specification applies to grid-connected inverter. 2

Normative references

The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. GB 4208-2008 Degrees of protection provided by enclosure(IP code)(IEC 60529:2001,IDT) GB 7260.2-2009 Uninterruptible power system(UPS) – Part 2: Electromagnetic compatibility (EMC) requirements (IEC62040-2：2005,IDT) GB 10593.1-2005 Measuring methods of environmental parameters for electric and electronic products - Part 1: Vibration GB/T 191-2008 Packaging storage icon logo GB/T 2423.1-2008 Basic environmental testing procedures of electrical and electronic products test A：Low-temperature test method (IEC 60068-2-1:2007, IDT) GB/T 2423.2-2008 Basic environmental testing procedures of electrical and electronic products test B：high-temperature test method(IEC 60068-2-2:2007,IDT) GB/T 2423.3-2006 Basic environmental testing of electrical and electronic products part 2 test method test Cab：Constant damp heat test(IEC 60068-2-78:2001,IDT) GB/T 3859.2-1993 Application guidelines of semiconductor converter(IEC 60146-1-2:1991,EQV) GB/T 12325-2008 Power quality supply voltage allowable deviation GB/T 12326-2008 Power quality-Voltage fluctuation and flicker GB/T 13384-2008 General specifications for packing of mechanical and electrical product GB/T 14549-1993 Power quality utility power grid harmonics GB/T 15543-2008 Power quality three-phase voltage allowable degree of unbalancedness GB/T 17626.2 Electromagnetic Compatibility Testing and measurement techniques The Immunity Test to Electrostatic Discharge (IEC 61000-4-2:2001,IDT) GB/T 17626.3 Electromagnetic Compatibility The Immunity Test to Radiated radio-frequency electromagnetic field(IEC 61000-4-3:2002,IDT) GB/T 17626.4 Electromagnetic Compatibility The Immunity Test to Electrical fast transient/burst(IEC 61000-4-4:2004,IDT) GB/T 17626.5 Electromagnetic Compatibility The Immunity Test to Surge (IEC 61000-4-5:2005,IDT) GB/T 17626.6 Electromagnetic Compatibility The Immunity Test to conducted disturbances, induced by radio-frequency fields(IEC 61000-4-6:2006,IDT)

CGC/GF004:2011(CNCA/CTS 0004-2009A) GB/T 17626.8-2006 Electromagnetic Compatibility Testing and measurement techniques Power frequency magnetic field immunity test(IEC 61000-4-8:2001,IDT) GB/T 17626.11-2008 Electromagnetic Compatibility The Immunity Test to Voltage Dips, Short Interruptions and Voltage Variations(IEC 61000-4-11:2004,IDT) GB/T 17626.12-1998 Electromagnetic Compatibility Testing and measurement techniques Oscillatory waves immunity test(IEC 61000-4-12:1995,IDT) GB/T 17626.14-2005 Electromagnetic Compatibility Testing and measurement techniques Voltage fluctuation immunity test(IEC 61000-4-14:2002,IDT) GB/T 18479-2001 Terrestrial photovoltaic(PV) power generating systems General and guide(IEC 61277:1995,IDT) GB/T 20514-2006 Photovoltaic systems Power conditioners Procedure for measuring efficiency (IEC 61683:1999,IDT) IEC 62109-1-2010 Safety of power converters for use in PV power systems Part 1: General requirements IEC 62109-2-2010 Safety of power converters for use in PV power systems Part 2: Particular requirements for inverters EN 50530-2010 Overall efficiency of grid connected photovoltaic inverters IEC 60990-1999 Methods of measurement of touch current and protective conductor current IEC 62116-2008 Test procedure of islanding prevention measures for utility-interconnected photovoltaic inverters Q/GDW 617-2011 Technical rule for photovoltaic power station connected to power grid Q/GDW 618-2011 Test procedures for photovoltaic power station connected to power grid 3

Terms and definitions

For this technical specification, the following terms and definitions apply. 3.1

photovoltaic grid-connected inverter

Equipment that converts direct current (dc) from solar cells to alternating current (ac).

Note1:Mentioned inverter in this specification refer to grid-connected PV inverter Note2:Technical requirements and test methods in the specification do not apply to the inverter of AC MODULE

3.2

photovoltaic array simulator

Current source that simulates static and dynamic PV array current and voltage characteristics. 3.3

inverter AC output terminal

Connection point of inverter, local ac load and grid. 3.4

maximum power point tracking

Automatic adjustment in order to abtain the utmost power output from connected PV array, by tracking and controlling the variation of output voltage and current,which resulting from the variation of surface temperature and solar irradiation of PV module.

CGC/GF004:2011(CNCA/CTS 0004-2009A) 3.5

Maximum powder point tracking efficiency

ratio of the energy drawn by the device under test within a defined measuring period TM to the energy provided theoretically by the PV simulator in the maximum power point (MPP):

where PDC(t) instantaneous value of the power drawn by the device under test; PMPP(t) instantaneous value of the MPP power provided theoretically by the PV simulator 3.6

conversion efficiency, energetic (ηconv)

ratio of the energy delivered by the device under test at the AC terminal within a defined measuring period TM to the energy accepted by the device under test at the DC terminal:

where PAC(t) instantaneous value of the delivered power at the AC terminal of the device under test; PDC(t) instantaneous value of the accepted power at the DC terminal of the device under test 3.7

overall(total) efficiency

ratio of the energy delivered by the device under test at the AC terminals within a defined measuring period TM to the energy provided theoretically by the PV simulator:

3.8

islanding

A state in which a portion of the electric utility grid, containing load and generation, continues to operate isolated from the rest of the grid. 3.9

intentional islanding

According to a pre-configured control strategy, a plan to place an island effect. 3.10

unintentional islanding

Unplanned and non-controlled island effects occurring. 3.11

anti-islanding

CGC/GF004:2011(CNCA/CTS 0004-2009A) Must not unplanned island effect Note1: while non-planned island effect occuring, due to system power state was unknown, it will cause the following adverse effects:1 it is likely to endanger for staff and users of Power line maintenance. Note2: power Interfere with the normal switch on Note3: Power do not control islands voltage and frequency, thereby equipments of distributions and users will be damaged. 3.12

simulated utility

It is used for the test device of public power grid and its voltage and frequency are adjustable. 3.13

quality factor, Qf

A measure of the strength of resonance of the islanding test load. Note:In a parallel resonant circuit, such as a load on a power system

Q R CL f

………………………………….

(1)

Where: Qf is quality factor R is effective load resistance C is reactive load capacitance (including shunt capacitors) L is reactive load inductance With C and L tuned to the power system fundamental frequency, Qf for the resonant circuit drawing real power, P, reactive powers Qf, for inductive load and Qc for capacitive load, Qf can be determined by

Qf  PqL  PqC P where P is real power Qf is inductive load Qc is capacitive load Note: In a parallel resonant circuit PqC  PqL 。 Let PqC  Pq ，

Qf  Pq P 3.14

resonant frequency

In a parallel resonant circuit, such as a load on a power system

f 

1 2 LC

Where f is resonant frequency L is inductive load C is capacitive load Note: while Parallel RLC circuit resonanting, capacitive and inductive reactive power are equal, so parallel RLC resonant circuit is equivalent to a pure resistance.

CGC/GF004:2011(CNCA/CTS 0004-2009A) 3.15

temporary

Used to quantify the duration of short-term changes, refers to the time range 3s ~ 1min. 4

Product Categories

4.1 4.1.1

Product type According to grid-type

a. single-phase inverter b. three-phase inverter c. multi-phase inverter 4.1.2

According to the installation environment

a. indoor type b. outdoor type 4.1.3 According grid-connected methods a. reversible flow type b. irreversible flow type 4.1.4

According to means of electrical isolation

a. isolated type b. non-isolated type 4.1.5

According to voltage levels of connected grid

a. low voltage type b. medium-high voltage type 4.1.6

According to emission limits

a. A-type inverter A type inverter is not household inverter and inverter that not directly connected to the residential facilities for low-voltage supply network. Sales of this type of inverters should not be limited. But the following contents should be included in the operation instruction: Warning: This is an A-type inverter product. It may cause radio interference in home environment. At this point, the user may need additional measures. b. B-type inverter B-type inverter apply to all occasions, including home environment as well as all facilities which directly connect to residential low-voltage power supply network. 4.2 Output power Characteristics Rating values of inverter output power is priority to the following values(units kw). 4.2.1 Single-phase inverter module

CGC/GF004:2011(CNCA/CTS 0004-2009A) 0.5; 1.5; 2.5; 3; 5; 6; 7; 8; 9. 4.2.2

Three-phase inverter module

10; 30; 50; 100; 250; 500; 1000. 5

Technical requirements

5.1

Use conditions

Unless otherwise agreed upon by the manufacturer/suppier and purchaser, inverter should comply prescribed performance requirements in 5.1.1 ~ 5.1.2 in this specification. For the terms of the agreement, the test should be performed in accordance with the terms. 5.1.1 Environmental conditions of normal use a. Temperature: Indoor type is -20 ℃ ~ +40 ℃, outdoor type is -25 ℃ ~ +60 ℃ (no direct sunlight); relative humidity ≤ 90%, non-condensing; b. Altitude is not more than 1000m; when altitude> 1000m, inverter should be derating used according to the reqirement of GB / T 3859.2; c. No severe vibration impact, the vertical gradient ≤ 5 º; d. No conductive explosive dust, corrosion of metals and destruction of insulating gases and steam exist in the working environment. 5.1.2 Power conditions of normal use a. Absence of other provisions, inverter should be able to run in following grid conditions Utility grid harmonic voltage should not exceed the limits in Chapter 4 of GB / T 14549. Total harmonic voltage distortion≤5%. Odd harmonic voltage distortion≤4%. Even harmonic voltage distortion≤2%. b. Three-phase inverter AC output voltage unbalance should not exceed GB / T 15543 specified value, allowing a value of 2%, short-term should not exceed 4%. c. For AC output voltage of 20kV or less, three-phase voltage Tolerance is 10% of the rated voltage, 220V single-phase voltage Tolerance is +10%, -15% of rated voltage. Other cases, Power Grid Voltage Tolerance should conform to GB / T 12325. d. Power Grid Frequency Tolerance should conform to GB / T 15945,which is no more than 0.5Hz. 5.1.3

Special conditions

If the inverter is not used in the conditions of 5.1.1 and 5.1.2, users should reach agreement with the suppliers. 5.2

Quality of the body and structure

Inverter structure and manufacturing quality of cabinet itself, the main circuit connection, installations of secondary lines and electrical components shall meet the following requirements. a. The components of rack assembly should be consistent with the technical requirements. b. Paint plating should be firm, smooth, non-peeling,rust and cracking phenomena and so on.

CGC/GF004:2011(CNCA/CTS 0004-2009A) c. d. e. f.

Rack panels to be flat, text and symbols to be clear, clean, standardize and correct. Signs and markings should be complete and clear. A variety of switches should be easy to operate, flexible and reliable. Cabinet should have the appropriate protective measures to prevent the operator from contacting with the electrode part directly, including AC and DC connection terminals and the electrode of various electrical components.

5.3 5.3.1

Performance indicators Conversion efficiency

Maximum conversion efficiency of transformerless inverter should not be less than 96%. Maximum conversion efficiency of transformer inverter should not be less than 94%. Note: Maximum power point tracking efficiency (including static and dynamic) will also affect the inverter effectively use electric energy geneated by photovoltaic power system. This need scientific test. Specific limits based on actual test data will be further clear.

5.3.2

Grid-connected current harmonic

The PV system output should have low current-distortion levels to ensure that no adverse effects are caused to other equipment connected to the utility system. Total harmonic current distortion shall be less than 5 % at rated inverter output. Each individual harmonic shall be limited to the percentages listed in Table 1 and 2. Under other loads, current of the inverter into the power grid should not exceed the acceptable harmonic current rated inverter output. Table 1 – Current distortion limits for odd harmonics Odd harmonics

Distortion limit

3 through 9

Less than 4.0 %

11 through 15

Less than 2.0 %

17 through 21

Less than 1.5 %

23 through 33

Less than 0.6 %

35 and above

Less than 0.3%

Table 2 – Current distortion limits for even harmonics Even harmonics

Distortion limit

2 through 10

Less than 1.0 %

12 through 16

Less than 0.5 %

18 through 22

Less than 0.375 %

24 through 34

Less than 0.15 %

36 and above

Less than 0.075 %

Note: As the voltage distortion may lead to more severe current distortion, harmonic test may be has some problems. Injected harmonic currents shall not include any harmonic currents caused by harmonic voltage from grid not connected to the PV system. Tests meeting the above requirements may be regarded as ok, no further tests.

CGC/GF004:2011(CNCA/CTS 0004-2009A) 5.3.3

Power factor

The PV system shall have a power factor no less than 0.98(leading or lagging) when the output active power is greater than 50 % of the rated inverter output power. Power factor should be no less than 0.95(leading or lagging) when the output active power is between 20%~50%. Average Power Factor(PF)is：

PF 

Pout 2 2 Pout  Qout

where：

Pout —Total the inverter output active power； Qout —Total the inverter output reactive power.

Note : Specially designed systems that provide reactive power compensation may operate outside of this limit with utility approval. 5.3.4

Response to abnormal voltage

The inverter should work properly when the power grid voltage is in the following range. The single-phase voltage (220V) deviation is between -15% and +10% of rated voltage and three-phase voltage (380V) deviation is between -10% and +10% of rated voltage. The inverter of other output voltage should be able to work properly in the corresponding allowable grid voltage deviation according to GB / T 12325. When the output voltage of inverter deviates outside the conditions specified in Table 3, the photovoltaic system shall cease to energize the utility distribution system and send warning signal. The respond time to abnormal voltage should comply with the requirements specified in Table 3. Inverter should restart and operate normally after the grid voltage recovers to the allowable range. This applies to any phase of a multiphase system. Table 3 – Response to abnormal voltage a Voltage (at point of utility connection) Maximum trip time V < 0.5 * Vnominal

0.1s

50 % Vnominal ≤ V < 85 % Vnominal

2.0s

110 % Vnominal < V < 135 % Vnominal

1.0s

135 % Vnominal ≤V

0.05s

a

: Effective voltage

Note 1: Trip time refers to the time between the abnormal condition occurring and the inverter ceasing to energize the utility line. Note 2: When in the Table 3 the response time for abnormal voltage and other protection methods conflict, give priority to other protection. 5.3.5

Response to abnormal frequency

When the grid frequency various, the inverter should comply with the requirments in Table 4. When the inverter cease to energize the utility distribution system, it should restart and operate normally after the grid frequency recovers to the allowable range.

CGC/GF004:2011(CNCA/CTS 0004-2009A)

Table 4 – Response to abnormal frequency Frequency range Inverter response

5.3.6

＜48Hz

Inverter stops operating within 0.2 seconds

48-49.5Hz

Inverter stops operating after 10 minutes working

49.5-50.2Hz

Inverter works normally

50.2-50.5Hz

Inverter stops operating after 2 minutes working, It is forbid to connect the grid

＞50.5Hz

Inverter stops operating after 0.2 seconds working, It is forbid to connect the grid

DC Component

When inverter operate at rated power connecting to the grid, DC component from grid feeded inverter should not exceed 0.5% of output current rating of or 5mA, whichever is the larger value should be. 5.3.7

Voltage unbalance degree

When inverter operate connecting to the grid (three phase output), three-phase voltage unbalance of public connection point of inverter accessing to the grid does not exceed the limits specified in GB / T 15543. Negative sequence voltage unbalance of common connection point should not exceed 2%, short-term should not exceed 4%; the negative sequence voltage unbalance caused by inverter does not exceed 1.3%, short-term not more than 2.6%. 5.3.8

Noise

While inputting rated voltage and the inverter is under full load operation , noise is measured by the sound level meter at a distance of 1m in level position away from device. For the noise level is greater than 80dB, conspicuous position of the inverter should affixed "hearing damage" warning signs. The guidance should be given in the instructions to reduce hearing damage. 5.4

Electromagnetic Compatibility

5.4.1 5.4.1.1

Emission requirements Conducted emission test

In the frequency range of 0.15 MHz to 30 MHz, the disturbance voltage limit of auxiliary power supply port of A-type and B-type inverter is listed in table 5. The disturbance voltage of auxillary power supply port should not exceed the value specified in table 5. Table 5 In the frequency range of 0.15 MHz to 30 MHz, the disturbance voltage limits of auxiliary power supply port for A-type and B-type inverter Frequency Range MHz

Limit dBμV

CGC/GF004:2011(CNCA/CTS 0004-2009A) A-type quasi peak average value 0.15～0.50 79 66 0.50～5.0 73 60 5.0 ～30.0 73 60 a Limit decreases with logarithm of the frequency. 5.4.1.2

quasi peak a 66～56 56 60

B-type average value a 56～46 46 50

Radiated Emission test

In the frequency range of 30MHz to 1000MHz, the radiated emission limit of A-type and B-type inverter listed in table 6. The radiated emission should not exceed the value specified in table 6. Table 6

In the frequency range of 30MHz to 1000MHz, the radiated emission limits of A-type and B-type inverter

Frequency Range MHz 30～230 230～1000 5.4.2 5.4.2.1

Quasi peak limit dB(μV/m) A-type, 10m test distance 40 47

B-type, 10m test distance 30 37

Immunity requirements Electrostatic discharge (ESD) immunity test

Inverter should be subjected to class 3 at least in GB/T 17626.2-2006, and the test results should meet the requirements of class b in GB/T 17626.2-2006. 5.4.2.2

Radiated radio-frequency electromagnetic field (RFEMS) immunity test

Inverter should be subjected to class 3 at least in GB/T 17626.3-2006, and the test results should meet the requirements of class a in GB/T 17626.3-2006. 5.4.2.3

Electrical fast transient/burst (EFT) immunity test

Inverter should be subjected to class 2 at least in GB/T 17626.4-2008, and the test results should meet the requirements of class a in GB/T 17626.4-2008. 5.4.2.4

Voltage fluctuations immunity test

Inverter should be subjected to class 2 at least in GB/T 17626.14-2005, and the test results should meet the requirements of class a in GB/T 17626.14-2005. 5.4.2.5

Surge immunity test

The auxiliary power supply port of inverter should be subjected to 1.2/50μs surge signal, line to line±1kV,line to earth±2kV, and the test results should meet the requirements of class b in GB/T 17626.5-2008. 5.4.2.6

Conducted disturbances, induced by radio-frequency fields immunity test

Inverter should be subjected to class 3 at least in GB/T 17626.6-2008, and the test results should

CGC/GF004:2011(CNCA/CTS 0004-2009A) meet the requirements of class a in GB/T 17626.6-2008. 5.4.2.7

Power frequency magnetic field immunity test

Power frequency magnetic field immunity should use GB / T 17626.8-2006 test level in the stable and sustainable magnetic field (see Table 7), the inverter should be able to withstand the selected level of power frequency electromagnetic field test in stable and continuous magnetic field. Table 7 Magnetic field test levels level magnetic field intensity， A/m 1

1

2

3

3

10

4

30

5

100

1)

X

Special

1) Open level, can be given in the product specification. For type-A inverter which expects to connect to the grid and the industrial working environment, power frequency magnetic field immunity should use test level 4 of GB / T 17626.8-2006 in the stable and sustainable magnetic field. The inverter should be able to withstand stable and sustainable power frequency magnetic field of selected test level. For type-B inverter which expects to connect to commercial and light industrial environments, power frequency magnetic field immunity should use test level 3 of GB / T 17626.8-2006 in the stable and sustainable magnetic field. The inverter should be able to withstand stable and sustainable power frequency magnetic field of selected test level. 5.4.2.8

Oscillatory waves immunity test

According to the working environment, inverter should be tested for the specified test level in GB / T 17626.12 oscillatory wave immunity test. Test criterion should be made respectively according to different working environment. 5.5

Protection functions

5.5.1 5.5.1.1

Power failure protection Anti-islanding protection

The inverter should have the function of anti-islanding protection. The inverter must cease to energize the utility line with warning signals within 2 s when the grid which inverter connected to fails to power supply. Refer o Appendix B for anti-islanding protection scheme selection rule 5.5.1.2

Low voltage withstanding capability

The medium and high voltage inverters specifically applicable to large PV power stations shall have certain withstanding capability to the voltage abnormality in order to avoid the disconnection

CGC/GF004:2011(CNCA/CTS 0004-2009A) when the grid voltage is abnormal and thus brings about grid power unstability. When the voltage at the POI is within the area of the voltage outline or above shown in Figure 1, the PV power station must ensure the continuous interconnection operation; if the voltage at the POI is below the voltage outline in the figure, the PV power station is allowed to stop the power feeding into the grid line.

Voltage drop due to abnormal grid

PV power station must operate in connection with grid

PV power station may be cut away from the grid

Figure 1 Low Voltage Withstanding Capability Requirement for Large and Medium PV Power Station UL0: the minimum voltage limit value in normal operation UL1 : the lower voltage limit to be withstood T1: the interconnection time necessary to be kept when the voltage falls to UL1 T2 : the interconnection time necessary to be kept when the voltage falls to UL0. The determination of UL1, T1 and T2 shall consider such actual situations as protection and reclosing action time, etc. The actual limit should be in accordance with the technical specifications of relevant departments in charge of grid access. 5.5.1.3

AC side short-circuit protection

The inverer should have the function of short-circuit protection. When output short-circuit was detected, the inverter should cease to energize the gird. If twice of output short circuit protction is detected in 1 minute, the inverter is forbidden to connected to the grid sautomatically 5.5.2

Prevention of anti-discharge protection

When the inverter DC side voltage is lower than the permitted work scope or inverter is turned off, there should be no reverse current in the inverter DC side. 5.5.3

Reverse polarity protection

CGC/GF004:2011(CNCA/CTS 0004-2009A) When the photovoltaic array in reverse polarity, the inverter should be protected from damage. Polarity is received, the inverter should be able to work properly. 5.5.4

DC current overload protection

When the photovoltaic array output power exceeds allowed maximum DC input power of inverter, the inverter should work in allowed maximum AC output power in limiting current automatically. In the condition of 7 hours continuous operating or temperature exceeds the allowable value, the inverter is permitted to cease to energise the grid. Normally, the inverter should be able to work properly. Note: overload protection of photovoltaic grid-connected inverter with maximum power point tracking control is that working point deviate from maximum power point of photovoltaic array. 5.5.5

DC over voltage Protection

When the inverter DC input voltage is higher than the maximum DC Array allowable input voltage, the inverter should not start or should stop working within 0.1s (running inverter) with warning signals. After the DC side voltage recover to the allowable working voltage, the inverter should start normally. 5.6

Array insulation resistance detection

5.6.1 Array insulation resistance detection for inverters for functionally grounded arrays Inverters for use with ungrounded arrays shall have means to measure the DC insulation resistance from the PV input (array) to ground before starting operation.If the insulation resistance is less than R = (VMAX PV/30 mA) ohms, the inverter： a) For isolated inverters, shall indicate a fault (operation is allowed); the fault indication shall be maintained until the array insulation resistance has recovered to a value higher than the limit above; b) For non-isolated inverters, or inverters with isolation not complying with the leakage current limits in the minimum inverter isolation requirements, shall indicate a fault, and shall not connect to the grid; the inverter may continue to make the measurement, may stop indicating a fault and may connect to the grid if the array insulation resistance has recovered to a value higher than the limit above. 5.6.2 Array insulation resistance detection for inverters for functionally grounded arrays Inverters that functionally ground the array through an intentional resistance integral to the inverter, shall meet the requirements in a) and c), or b) and c) below: a) The value of the total resistance, including the intentional resistance for array functional grounding, the expected insulation resistance of the array to ground, and the resistance of any other networks connected to ground (for example measurement networks) must not be lower than R = (VMAX PV/30 mA) ohms. The expected insulation resistance of the array to ground shall be calculated based on an array insulation resistance of 40 MΩ per m2, with

CGC/GF004:2011(CNCA/CTS 0004-2009A) the surface area of the panels either known, or calculated based on the inverter power rating and the efficiency of the worst-case panels that the inverter is designed to be used with. b) As an alternative to a), or if a resistor value lower than in a) is used, the inverter shall incorporate means to detect, during operation, if the total current through the resistor and any networks (for example measurement networks) in parallel with it, exceeds the residual current values and times in Table 8 and shall either disconnect the resistor or limit the current by other means. If the inverter is a non-isolated inverter, or has isolation not complying with the leakage current limits in the minimum inverter isolation requirements, it shall also disconnect from thegrid. c) The inverter shall have means to measure the DC insulation resistance from the PV input to ground before starting operation. 5.7 5.7.1

Array residual current detection General

In a non-isolated inverter, or an inverter with isolation that does not adequately limit the available touch current, the connection of the mains to earth (ie the earthed neutral) provides a return path for touch current if personnel inadvertently contact live parts of the array and earth at the same time. The requirements in this section provide additional protection against this shock hazard through the application of 5.7.4 or 5.7.5, except neither is required where isolation is provided that limits the available touch current to less than 30mA. Ungrounded and grounded arrays can create a fire hazard if a ground fault occurs that allows excessive current to flow on conductive parts or structures that are not intended to carry current. The requirements in this section provide additional protection against this fire hazard by is provided that limits the application of 5.7.4 or 5.7.5, except neither is required where available current to less than - 300mA for inverters with rated continuous output power ≤ 30kVA, or - 10mA per kVA of rated continuous output power for inverters with rated continuous output power rating > 30kVA 5.7.2

30mA touch current type test for isolated inverters

The inverter must connect and operate under REFERENCE TEST CONDITIONS, except that the DC supply to the inverter must not have any connection to earth, and the mains supply to the inverter must have one pole earthed. It is acceptable (and may be necessary) to defeat array insulation resistance detection functions during this test. The touch current measurement circuit of IEC 60990, Figure 4 is connected from each terminal of the array to ground, one at a time. The resulting touch current is recorded and compared to the 30mA limit. 5.7.3 Fire hazard residual current type test for isolated inverters

CGC/GF004:2011(CNCA/CTS 0004-2009A) The inverter must connect and operate under REFERENCE TEST CONDITIONS, except that the DC supply to the inverter must not have any connection to earth, and the mains supply to the inverter must have one pole earthed. It is acceptable (and may be necessary) to defeat array insulation resistance detection functions during this test. An ammeter is connected from each terminal of the array to ground, one at a time. The current is recorded and compared to the limit in 5.7.1. 5.7.4 Protection by application of RCD’s The requirement for additional protection in 4.201.3.1 can be met by provision of an RCD with a residual current setting of 30mA, located between the inverter and the mains. When required by Part 1, the RCD must be type B rather than type A or type AC. The RCD may be provided integral to the inverter, or may be provided by the installer if details of the rating, type, and location for the RCD are given in the installation instructions per 5.3.2.208. 5.7.5 Protection by residual current monitoring The inverter shall provide residual current monitoring that functions whenever the inverter is connected to the MAINS with the automatic disconnection means closed. The residual current monitoring means shall measure the total (both a.c. and d.c. components) RMS current. For different inverter types, array types, and inverter isolation levels, detection may be required for excessive continuous residual current, excessive sudden changes in residual current, or both, according to the following limits: a) Continuous residual current: The inverter shall disconnect within 0.3 seconds and signal a fault if the continuous residual current exceeds: - 300mA for inverters with continuous output power rating _ 30kVA - 10mA per kVA of rated continuous output power for inverters with continuous output power rating > 30kVA b) Sudden changes in residual current: The inverter shall disconnect from the MAINS within the time specified in Table 8 if a sudden change in residual current is detected exceeding the value in the table. Table 8 Response time limits for sudden changes in residual current

Residual current sudden change

Max time to inverter disconnection from the MAINS

30mA

0.3s

60mA

0.15s

150mA

0.04s

5.8 Communication

CGC/GF004:2011(CNCA/CTS 0004-2009A) Inverter should be set up local communication interface. Communication interface should be used with fixed measures to protect effective connection between connecting table and equipment. Communication port should have resistance to electromagnetic interference, and easy to form a network. 5.9 Auto on / off Inverter should be automatically startup and shutdown according to sunrise and sunset. 5.10

Soft-start

Inverter starts running, the output power should be slowly increasing, that is rate of change of the output power should be adjustable. Output current has no impact. 5.11 5.11.1

Insulation resistance and dielectric strength test Insulation resistance

The insulation resistance between input circuit to the ground, the output circuit to the ground of inverter and input circuit and output circuit should not be less than 1MΩ. Insulation resistance is only reference for dielectic strength test. 5.11.2 Dielectric strength test Inverter input circuit to ground, the output circuit to ground and input circuit to the output circuit should withstand 50Hz sinusoidal AC voltage or equivalent DC voltage for 1 min. The root-mean-square values of test voltage is listed in Table 4. In the test, no breakdown and arcing shall occur. The leakage current 90% the range of the DC input voltage

The voltage and frequency trip values specified by the manufacturer

50%±10% the the range of the DC input voltage

The voltage and frequency trip values are set as the rated values