MNRE Invites Suggestions on Draft Guidelines for Series Approval of Inverters for Lab Testing

These guidelines are applicable for SPV based off-grid, grid-tie and hybrid inverters of capacities up-to 150KW.

After issuing draft guidelines for storage batteries, the Ministry of New & Renewable Energy (MNRE) has invited comments or suggestions from public and related stakeholders on the guidelines drafted for series approval of inverters for conducting lab testing.

Further, these guidelines have been prepared in consultation with experts from test labs, solar inverters industry and Bureau of Indian Standards, New Delhi.

Moreover, the interested stakeholders can provide their comments latest by April 19, 2019 at [email protected].

“The guidelines are issued to facilitate labs/manufacturers in formation of series of products for approval of product family including change in design, materials, etc. for the testing of Solar Inverters in the test labs for compulsory registration with BIS for implementation of the Solar Photovoltaics Systems, Devices and Component Goods Order 2017,” said MNRE in its notification.

The Ministry further added that, these guidelines are applicable for SPV based off-grid, grid-tie and hybrid inverters of capacities up-to 150KW.

Here’re a few guidelines that will be followed for conducting tests on solar inverters as per standards included in the said order by the test labs:

• The series guidelines are based on the following design and construction considerations:
  1. The Inverters having PV voltage rated 1000/ 1100 Vdc max and AC voltage 415Vac Nominal.
  2. Both Hardware and Firmware are the same as declared by the Inverter Manufacturer. The Firmware can have different limit settings as per the model rating in the series.
  3. Products having different Hardware Architecture and Firmware functionality shall be tested separately. Within the Family the components with different ratings (Power/current) can be allowed provided the Inverter with max rated component (such as EMC filters, Capacitors, Transformers, Inductors, IGBT/Mosfets, etc.) is tested.
  4. All the models under one family shall have same rated Input/Output voltage, Same frequency and No. of Phases at output, Same PCB design and layout, same power stage topology, same insulation class (low or high frequency transformer or transformerless), same control algorithm/firmware, Same cabinet design and class of construction. If the cabinet design architecture is changing between various models in the family (keeping the same Internal Hardware like PCB layout between various models in the family), then all the different cabinet designs are to be tested or verified for Ingress Protection by either testing it at NABL approved laboratories or test reports shall be submitted from ISO/IEC 17025/ILAC accredited laboratories.
  5. The Maximum rated Inverter within the family shall be considered as the representative test sample for all the models in that family for safety tests.
  6. Inverters having PV voltages rated 1100Vdc shall be tested at 1000V.
  7. Inverters having PV voltages rated greater than 1000Vdc and greater than 415Vac are not covered in these guidelines.

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Clause (IS 16221 (Part 1):2016)	List of Tests	Assistance of manufacturers for technical and operational issue of components
7.3.2.6	Working voltage and DVC	To tap out points and connect oscilloscopes at various internal auxiliary and Gate drive/control power supplies
7.3.9	Protection against shock hazard due to stored energy	To tap out point across the total bus capacitors and connect oscilloscope
9.2.2	Limited power source tests	To overload the auxiliary, Gate drive/control power supplies with loads to check the maximum VA power
7.5.2	Voltage test (dielectric strength test)	To remove some components like MOVs, X/Y capacitors or branch circuits which is connected across the ground
4.4.4.6	Backfeed current test for equipment with more than one source of supply	To put current probes after the DC fuses in the input side and before the contactor/relay in the AC output side of the inverter.
4.6	Backfeed voltage protection	To tap out point to connect voltage probes after the DC fuses in the input side and before the contactor/relay in the AC output side of the inverter.
4.3.2.1	Maximum temperatures – General	To put thermocouples in the all the critical components without damaging the inverter functioning
4.4.4 Method 1	Single Fault conditions to be applied	To open or short the critical components which is identified as its failure may lead to shock or Fire hazard. Example: DC bus capacitor short, IGBT D-S short ( C-E), IGBT G-D short ( G-E), IGBT open gate ( Disable the IGBT by shorting the G -E), output current measurement (open any one phase), output voltage measurement (open any one phase), control circuit failure (remove power from control circuit)