Short Duration Undervoltage Disturbance Ride-Through Test Procedure
Background
AEMO has identified through analysis of recent power system events, that a proportion of distributed solar PV (DPV) disconnect in response to short duration transmission undervoltage disturbances. Given the levels of DPV installed in South Australia, a severe but credible fault near the Adelaide metropolitan area could cause disconnection of up to half the distributed PV in the South Australian region.
Under specific conditions this would leave AEMO with very few courses of action available for secure operation of South Australia. These findings have been highlighted as part of the recently published: Renewable Integration Study report, the Minimum operational demand thresholds in South Australia Technical report and recognised by the South Australian Government and SA Power Networks (SAPN).
To reduce the potential for disruption and improve power system security, most immediately in South Australia, AEMO:
to ensure inverters compliant with AS/NZS 4777.2:2015, and DPV by extension, respond appropriately during short duration undervoltage disturbance events to mitigate any further potential risks to power system security.
Development and publication of a VDRT Test Procedure is part of AEMO’s broader strategy to address DPV inverter behaviour, which also includes:
However, AEMO considers there is a pressing need to accelerate implementation of the VDRT Test Procedure in South Australia.
Test Procedure
Following feedback from the consultation, the final test procedure has been developed. The intent of the procedure is to verify the behaviour of an inverter energy system within a distributed energy resource (DER) installation during a short duration undervoltage disturbance.
The test procedure should be applied in conjunction with existing product certification testing for compliance with AS/NZS 4777.2:2015 and has been developed as a supplementary test.
Implementation
The following page has been published by the South Australian Office of the Technical Regulator with details on inverter connection requirements, the scope and timing of application, how to submit inverter test results and the list of approved inverters. This information is relevant for inverter manufacturers and installers that must meet South Australia’s inverter standard requirements:
Frequently Asked Questions
-
Q. If my inverter has been tested and complies with AS/NZS 4777.2:2020, do I still need to complete this short duration undervoltage ride-through test procedure?
-
Q. I have internal testing to show my inverters comply with the Voltage Ride Through requirements. Can my inverters be sold in South Australia while getting the testing verified by an accredited test lab?
-
Q. If an inverter already meets the requirements of AS/NZS 4777.2:2015, and has completed the test associated with the standard, does it need to complete the VDRT test?
-
Q. Once the VDRT test has been completed at an accredited test laboratory, where do the results need to be sent? Once test results have been reviewed and approved, where will compliant inverters be listed?
-
Q. What will happen when the new AS/NZS 4777.2:202X is published?
-
Q. Is type testing for a series of inverter acceptable?
-
Q. The AEMO test procedure Section 2.2 Undervoltage (V<) disconnection test in response to event duration exceeding trip delay time is similar to AS/NZS 4777.2 Appendix G2.2 Steps (h) to (l). Is meeting the AS/NZS 4777.2 G2.2 test sufficient?
-
Q. Can this update be achieved through inverter firmware upgrades?
-
Q. The standard only applies to newly installed inverters. How will this mitigate power system security risks currently being faced if the vast majority of installed DER/inverters do not meet the requirements?
-
Q. Will this standard apply to replacement inverters? Battery and PV inverters? And off-grid inverters?
-
Q. Will these changes increase costs for consumers?