MNRE Releases Draft Standards For Photovoltaic Grid Tie Inverters

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The Ministry of New and Renewable Energy (MNRE) has released the draft standards for “Technical requirements for Photovoltaic Grid Tie Inverters to be connected to the Utility Grid in India”.

The notice asks stakeholders to provide their inputs and comments to the Ministry positively by 30/4/2020.

The order states that “In order to ensure the quality and reliability relevant IS/IEC Standards covering safety, efficiency, environmental and islanding prevention measures tests for Utility-Interconnected Photovoltaic Inverters have been perused. Further, in order to make the process of testing simple and consistent, a view has been taken to develop an inclusive standard for Photovoltaic Grid Tie Inverters for complete performance evaluation for grid-interactive applications for quality and reliability assurance in Indian conditions.”

In Grid Interconnection Tests The PV system shall not inject DC greater than 0.5 % of the continuous maximum rated inverter output current into the utility interface when tested at 25%, 50%, 75%, and 100% of rated output power.

The purpose of this standard is to lay down requirements for interconnection of PV systems/inverters to the utility distribution system and to provide a test procedure to evaluate utility-interconnected photovoltaic (PV) power systems operating in parallel with the utility and utilizing static (solid-state) non-islanding inverters for the conversion of DC to AC. This standard applies to interconnection with the low-voltage and medium-voltage utility distribution system. 

As per the document, The grid test voltage shall be 230 V a.c. phase to neutral 50 ±0.1 Hz, unless otherwise specified. For environmental testing, the inverter shall be operated in nominal operating condition in an ambient of 50°C ± 2°C with a relative humidity of 93% ± 3% for a minimum time duration of 13 48hours. 

It is highlighted in the document that Single Phase inverter applicability may be debated for LVRT/HVRT

In response to utility recovery Following an abnormal voltage or frequency event that has caused the photovoltaic system to cease to energize, the photovoltaic system shall not energize the utility line for an adjustable time delay between 20 seconds and 300 seconds after the utility service voltage and frequency have recovered to within the ranges of Voltage between 85% Un and 110% Un and Frequency between 49.5Hz to 50.5Hz 

For inverters connecting to the utility system, the inverter shall comply with the limits in the applicable standard as follows: – IEC 61000-3-3 for inverters with rated current ≤16 A per phase and not subject to conditional connection, IEC 61000-3-11 for inverters with rated current ≤75 A per phase and subject to conditional connection, IEC 61000-3-5 for inverters with rated current >75A per phase and subject to conditional connection.

The MNRE series guidelines shall be referred to for selecting the samples from a single family of inverters and The equipment shall be connected and configured per the manufacturer’s instruction, where the outcome of testing could be affected.

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