On 15 December 2022, the Australian Energy Market Commission (AEMC) published a draft rule and determination that would revise the minimum access standards that specify the nature of the reactive current response that inverter-connected generators must provide in response to a fault. 

The draft rule would offer the following key benefits: 

• lower the cost of connecting renewable generators by lowering the amount of reactive current capability they would need to provide
• improve system security outcomes by establishing a better balance between response speed and stability 
• ensure the provision of voltage support equipment at least cost over time by acknowledging the role of NSPs in assessing the costs and benefits of these investments.

The draft rule would achieve this by making the following key changes to the rules: 

• It would lower the reactive current capability requirement to a ‘do no harm’ level that will require generators to inject or absorb reactive current at their connection point to ensure that they do not worsen voltage conditions after a disturbance 
• It would reformulate existing requirements to incentivise a fast and stable response by requiring that responses commence within 40 milliseconds and lengthen the rise time requirement from 40 ms to 80 milliseconds.
• It would clarify several other aspects of the rules to support faster connection negotiations between connecting generators, NSPs and AEMO

Submissions to the draft determination are due by 3 February 2023 

Background

The AEMC initiated consultation on a consolidated rule change request from two proponents, one from a consortium of wind turbine original equipment manufacturers and the other from Renewable Energy Revolution (RER) Pty Ltd on 26 May 2022. 

The Commission consulted on these issues together because they cover similar issues. Both proposed that the standards specifying the reactive current fault-response that should be required of connecting plant be changed and set at a level better reflects the locationally specific needs of the power system.

Inverter connected resources such as batteries currently have to demonstrate that they comply with the minimum access standards specified in Schedule 5.2.5.5 of the NER. Network service providers are not able to provide connection approval to parties that do not meet this minimum standard. 

RER’s proposal considered that the existing reactive current fault-response requirements are not appropriate for locations in the network with low inductance resistance ratios and recommended a move away from the current static maximum reactive current fault-response requirement of 100% of the unit’s maximum continuous current. Instead, they proposed a maximum reactive current response that is less than 100% and varies based on the impedance at the connection point described by the local reactance to resistance ratio.

The wind turbine OEMs’ proposal noted that the standards are set at an inappropriate level compliance is not defined in a way that is mutually understood by AEMO, TNSPs and connecting proponents inconsistencies exist between these and some related standards that make it difficult to comply with all of them. To address these issues, their proposal recommended that: 

• the minimum level of reactive current capability that generators have to install at the connection point be lowered to zero to resolve the risks to the commercial viability of new generation and investment duplication;
• the point of compliance assessment be shifted from the connection point to the generator unit terminals to resolve the challenges with controlling a generator's reactive current response
• the standards describing the characteristics of a response (i.e. how quickly the response should rise, and stabilise) be made less onerous
• resolve other issues that are creating uncertainties for the grid approvals process by clarifying potential conflicts between obligations to provide a reactive power response that helps maintain stable voltage levels and an active power response that helps maintain stable frequencies

The Commission consulted on the rule change proposals till 23 June 2022. After this, we held three technical working group meetings and invited all the parties that had made submissions to the consultation paper to provide feedback on the principles that should guide revision of these standards, options for revision and our preliminary views on the draft rule. 

The Commission extended the timeframe to make a draft determination to 15 December 2022 because there was a material change in circumstances that made this extension necessary.

Earlier, the timeline to make a draft determination was extended to 3 November 2022 upon commencement of the rule change process, due to the complexity of the issues raised in the rule change requests.