MNRE Prepares Blueprint for Streamlining Technical Specs for Solar Inverters

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MNRE Prepares Blueprint for Streamlining Technical Specifications for Solar Inverters

The Ministry of New and Renewable Energies (MNRE) has issued draft guidelines for standards relating to the technical specifications for grid-connected inverters. The ministry has asked the public and stakeholders for comments and contributions by April 30, 2020.

Solar inverters must be checked for safety, efficiency, environmental testing and grid connection aspects to ensure their quality and reliability. Against this background, the ministry has introduced relevant standards for safety, efficiency, environmental and island prevention measures for photovoltaic inverters connected to supply lines.

In order to make the test process simple and consistent, the focus was placed on the development of a comprehensive standard for grid-connected photovoltaic inverters for complete performance evaluation for grid-interactive applications to guarantee quality and reliability under Indian conditions.

The draft contains a detailed relationship between technical specifications and requirements as well as specifications for environmental tests. The ministry said the purpose of the standards is to set the requirements for connecting PV systems and inverters to the utility distribution system.

The standards also provide a test procedure for evaluating PV power systems operating in parallel with the utility company and for using static inverters without islanding to convert DC to AC. Islanding is the condition in which a decentralized generation system supplies a site with power even when grid power is not available. An anti-island inverter stops switching a supply system that is outside of its regular operating specifications with power after a certain period of time.

The draft added that when selecting samples from a single family of inverters, reference should be made to the MNRE series guidelines. In August 2019, the MNRE approved the series guidelines for grouping solar inverters. These guidelines were used for the tests in laboratories for the implementation of the quality control to the implementation, which was introduced in 2017. According to the guidelines, manufacturers will have to submit a declaration of the series of their products while submitting the samples of a specific series to Testing .

The draft contains routine tests that should be performed on all inverters by the manufacturer, and each inverter should be accompanied by a test report. These tests are:

  • Protection against abnormal voltage
  • Abnormal Frequency Protection
  • Response to the recovery of the utility

These tests are based on the assumption that the device meets the applicable requirements of this standard and can be carried out as a factory test or as part of a commissioning test, according to the draft directive.

For the harmonic test, the MNRE has proposed changing from the IEEE standard (Institute of Electrical and Electronics Engineers) to the IEC standard (International Electrotechnical Commission). Solar PV systems contain power electronic interfaces that generate a level of harmonics. These harmonics have a major impact on the operating efficiency and reliability of the system.

With regard to the grid connection test, the draft states that the PV system does not feed a direct current of more than 0.5% of the continuous maximum inverter output current into the supply interface when tested with 25%, 50%, 75% and 100% of the nominal current .

“The requirement does not apply to an inverter that is connected to one another via a grid frequency isolating transformer between the output of the inverter and the supply system,” added the MNRE.

With regard to grid management, the MNRE has proposed that the PV system connected to the low-voltage (LV) and medium-voltage (MV) lines can remain connected to the grid under low-voltage and high-voltage conditions.

Previously, Mercom wrote about the inverter manufacturers’ difficulties in gaining clarity about the ambiguous BIS certification process. Unavailability of laboratories, lack of testing facilities and staff, disproportionately high cost of testing, lack of series guidelines, and confusion regarding MNRE notifications were some of the issues that led to compliance with the order made for “Solar Photovoltaic Systems, Devices and Components Goods” have 2017 ”extremely difficult. In several interviews with inverter suppliers, Mercom found that the cost of BIS certification, in addition to the time-consuming process, is also a cause for concern for the inverter suppliers.

In January 2020, the ministry issued a notice extending the deadline for self-certification of solar inverters from December 31, 2019 to June 30, 2020 by six months. The government recognized the need for quality components in solar projects and had ordered this. The laboratories must carry out the tests for the mandatory registration with the Bureau of Indian Standards (BIS) to implement the quality order. Given various issues related to testing fees and the lack of available testing laboratories, the industry has sought more time for compliance since the directive was introduced.


Anjana is news editor at Mercom India. Prior to joining Mercom, she was senior editor, district correspondent, and editor for The Times of India, Biospectrum, and The Sunday Guardian. She previously worked for the Deccan Herald and the Asianlite as editor-in-chief and news editor. She has also contributed to The Quint, Hindustan Times, The New Indian Express, Reader’s Digest (UK edition), IndiaSe (Singapore-based magazine) and Asiaville. Anjana holds a Masters degree in Geography from North Bengal University and a Diploma in Mass Communication and Journalism from Guru Ghasidas University in Bhopal.

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