AS/NZS 4777.2 – Inverter Requirements standard

Background 

The rapid pace at which Distributed Energy Resources (DER) are being installed is resulting in significant amounts of decentralised generation entering the power grid.  This level of penetration brings opportunities for consumers to access new products and services, and a need to ensure that the power system alongside over two million DER installation can operate together. 

AEMO’s role as the market operator is to ensure a secure and reliable energy supply to all Australians regardless of whether they have DER installed or not. Through the uplift of key standards, AEMO will be able to fulfil this role and, in conjunction with work being undertaken on a two-sided marketplace, offer opportunities for participation in the energy market. 

What is AS/NZS 4777.2

Distributed energy resources are connected to the electricity grid via inverters. Inverters adjust how the DER attached to them interacts with the power grid and defines how these resources must perform under different system conditions. 

AS/NZS 4777.2 specifies the expected performance and behaviour of inverters at low voltages (such as households or small-scale commercial) and the necessary tests for compliance. At present, AS/NZS 4777.2 does not capture all the performance requirements needed to optimise and support a secure power system under high levels of DER penetration.

How will AS/NZS 4777.2 change

AEMO is currently participating in the revision of the standard to ensure that the behaviour of these small-scale generators support the reliable and secure operation of the power system, including:

  • Specifying the conditions in which the inverter should remain connected and generating power to the electricity grid or disconnect to help prevent major events. 
  • Optimising and coordinating parameters to maximise the value of the capabilities offered with ‘smart’ inverters to provide improved power quality to customers and grid support functions for networks. This will increase the hosting capacity of DER allowing more customers the opportunity for DER uptake. 
  • Defining the accuracy and stability of measurement systems used in inverters, to improve the reliability of performance characteristics providing guaranteed responses to different conditions.
  • Improving and introducing testing procedures to ensure enhanced device level compliance is met. 

These changes aim to align with international best practice and applying (where possible) similar performance capabilities as large-scale generation.

Inverter inspections 

AEMO has been collaborating with the Clean Energy Regulator (CER) and the Clean Energy Council (CEC) to incorporate inverter settings checks into the CER’s existing inspection program as part of its Small-scale Renewable Energy Scheme.  

It was identified that as much as 40% of grid-connected inverters installed with rooftop solar PV systems since 2016 do not comply with some of the mandatory settings prescribed in AS/NZS 4777.2:2015 and the relevant Distribution Network Service Provider (DNSP) connection agreements. This is causing issues for grid reliability and security that without rectification will limit consumers’ choice to invest in DER. 

The information collected through the inverter settings checks in the CER inspection program will provide insights to better understand reasons for non-compliance to AS/NZS4777.2 and assist in improving processes to minimise this. It will also help inform the standards and testing arrangements that are required in the future, and assist AEMO, the CEC, DNSPs, or state and territory regulators with compliance monitoring.  

Compliance with the standards, and ensuring all settings are correct, is essential to increase hosting capacity of rooftop solar PV and other DER on the grid in the coming years, while maintaining grid reliability.  

For more information on the Inverter inspections, please visit: 

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