How are photovoltaic inverters approved in Brazil?

The compulsory certification of inverters and other equipment for photovoltaic applications was regulated by Ordinance 004/2011 of INMETRO (National Institute of Metrology, Standardization and Industrial Quality), within the scope of SBAC (Brazilian Conformity Assessment System).

INMETRO Ordinance 004/2011 “establishes the minimum performance and safety requirements for photovoltaic solar energy systems and equipment; considering the need to establish equitable and publicly known rules for the manufacturing, import and commercialization of systems and equipment for photovoltaic energy.”

Currently, photovoltaic inverters (for off-grid and grid-tie applications) with nominal power up to 10 kW must be tested and certified in laboratories designated by INMETRO. Without certification, equipment cannot be sold in the country, whether nationally manufactured or imported.

The 10 kW limitation was mainly due to the technical restriction of national laboratories at the time of drafting the INMETRO ordinances. Currently, there are laboratories in the country capable of powers at least three times above the current limit. This new limit would be sufficient to cover most of the equipment used in micro and mini generation systems.

While the mandatory certification in the aforementioned power range is in force, equipment with nominal power above 10 kW is exempt from participation in the certification program established by INMETRO, but is not free from requirements for its use in the country. It has been a common requirement for electricity distributors to present certificates of conformity issued by international laboratories, even if the requirement does not apply by order of INMETRO to equipment.

In this article, we will focus on grid-tie inverters, used to connect photovoltaic systems to the electrical grid.

INMETRO ordinance 004/2011

According to the ordinance, its objective is to “establish the criteria for the Conformity Assessment Program for systems and equipment for photovoltaic energy, through the labeling mechanism, for use of the ENCE (National Energy Conservation Label), meeting the requirements of the PBE (Brazilian Labeling Program), aiming at energy efficiency and [an] adequate level of security.”

In addition to photovoltaic modules, off-grid inverters and batteries, the scope of application of the ordinance includes inverters for photovoltaic systems connected to the electrical grid up to 10 kW – as previously mentioned.

Two important terms stand out in the objectives of the ordinance: efficiency and safety. The main objective of INMETRO and the labeling and energy conservation programs is to ensure that equipment that reaches the end consumer has its efficiency and safety evaluated and certified by national laboratories.

Among the countless models of equipment available on the market, INMETRO's central concern is to present an efficiency classification that allows the consumer the power to choose the product that provides the best energy performance.

Furthermore, concerns about equipment safety are relevant for the consumer market and, when it comes to inverters for connection to the grid, also for electricity distributors.

How the approval procedure works

Manufacturers, importers or traders who wish to approve a specific brand or model of equipment must send two samples of the product to one of the laboratories designated by INMETRO.

The laboratories carry out the test sequences provided for in ordinance 004/2011 and issue a compliance report, with which the interested company can request the labeling of its product and the import license, as applicable. You steps for registering the product with INMETRO these are:

• Signing and sending the Labeling Commitment Term to INMETRO. According to section 9.1 of ordinance 004/2011, the equipment supplier must sign and send to INMETRO the term of commitment referred to here, declaring, with an indication of the quantity, its entire line of products and manufacturing models, for INMETRO's knowledge;
• Sending the labeling request and product samples to a laboratory (listed by INMETRO) chosen by the manufacturer;
• Carrying out tests and issuing a technical conformity report by the certifying laboratory;
• Request for product registration by the supplier in the INMETRO Orchestra system;
• Approval for use of ENCE (National Energy Conservation Label). After verifying the conformity of the product and in possession of the test report issued by a designated laboratory, INMETRO confirms the authorization to use the label on the product and publishes the data through efficiency tables available on its website.

Ordinance 004/2011 also provides that companies participating in the program (which already have their products approved) can file complaints against products that may be suspected of non-compliance.

According to section 7.1.5 of the ordinance, after receiving the complaint, INMETRO may determine that evidentiary tests be carried out in a designated laboratory.

The laboratory chosen by INMETRO to carry out the test to investigate the complaint will be responsible for selecting a product from the reported supplier, given that the test must be carried out in compliance with the evaluation and conformity requirements (RAC) of ordinance 004/2011 and specific technical standards.

Photovoltaic products approved and registered with INMETRO are listed at the following addresses:

• Photovoltaic modules;
• Batteries;
• Grid-tie inverters (for network connection);
• Off-grid inverters.

Assessment and compliance requirements for grid-tie inverters

In its annexes, INMETRO Ordinance 004/2011 presents the RACs (evaluation and conformity requirements) necessary for each type of product.

The products subject to a greater number of requirements and procedures are, without a doubt, grid-tie inverters, among all the products listed in the aforementioned ordinance.

Photovoltaic inverters for connection to the electrical grid (grid-tie) must be subjected to the following tests:

1. Flicker;
2. Continuous component injection;
3. Harmonics and waveform distortion;
4. Power factor;
5. Injection/reactive power demand;
6. Over/under voltage;
7. Over/under frequency;
8. Control of active power at over frequency;
9. Reconnection;
10. Out-of-phase automatic reclosing;
11. Active power modulation;
12. Reactive power modulation;
13. Disconnection of the photovoltaic system from the grid;
14. Supportability requirements for undervoltages resulting from faults in the network;
15. Protection against polarity reversal;
16. Overload;
17. Anti-islanding.

Tests 1 to 14 are covered by the standards ABNT NBR 16149:2013 – Photovoltaic Systems – Connection interface characteristics with the electrical distribution network, and ABNT NBR 16150:2013 – Photovoltaic Systems – Connection interface characteristics with the electrical distribution network distribution – Testing procedure and compliance.

Test 17 is carried out in accordance with the specific standard ABNT NBR IEC 62116:2012 – Anti-islanding test procedure for photovoltaic system inverters connected to the electrical grid.

In general, the tests provided for in the assessment and conformity requirements, except for the last three, concern the way in which the grid-tie inverter behaves when connected to the low-voltage electrical energy distribution network.

The concern of the tests is to evaluate the inverter's protection functions in case of over and under voltage, disconnection and reconnection of the network, injection of harmonics and direct current and reactive power control capacity, among other things.

Test 17 concerns the behavior of the inverter when the primary voltage source is disconnected (intentionally or unintentionally), with the risk of islanded operation of the inverter (a situation that must be avoided by protection mechanisms built into the equipment).

The concern of the anti-islanding requirement and the corresponding standard (ABNT NBR IEC 62116:2012) is to verify what happens when the inverter is physically connected to an electrical installation that is islanded, that is, isolated from a distribution network or of a generator that forms an electrical network (voltage reference generator).

The main issue linked to the islanded operation of photovoltaic inverters is the possibility of damage to people and equipment, either with the origination of dangerous overvoltages (outside acceptable values) or with the inadvertent electrocution of people during maintenance procedures.

Each of the requirements listed above requires dedicated testing protocols and equipment. Given the extent and complexity of the tests involved in the requirements, it is impossible to address them in a single document, which is why they will be covered in detail in articles subsequent to this one.