The Australian Energy Market Commission (AEMC) has made draft changes to the National Electricity Rules to clarify power system frequency arrangements for grid scale batteries to keep the system stable as thermal generators continue to retire.
These changes are set out in a draft determination for stakeholder consultation following a rule change request by the Australian Energy Market Operator (AEMO), to clarify obligations for batteries with a capacity of 5 megawatts and registered as ‘scheduled bidirectional units.
The AEMC sets the rules for the National Electricity Market (NEM) and provides independent expert energy advice to Australia’s State and Federal Governments. It is strongly focused on providing a framework for a secure electricity system and affordable electricity prices, particularly in light of current cost of living concerns.
An essential part of this work involves making rules to make sure that the power system remains secure in order to meet the needs of households and businesses over the coming years.
Frequency varies when the supply of electricity doesn’t exactly align with consumer demand. Uncontrolled changes in frequency can cause cascading blackouts.
Primary frequency response (PFR) refers to an automatic adjustment in the generation or consumption of electricity from a generator or load, triggered by changes in the system’s frequency. This response is becoming increasingly important as traditional thermal generators are progressively replaced by variable energy sources, such as wind, solar and batteries.
Pressure will continue to be placed on the electricity system as aging coal fired generation retires, creating the potential for security risks. The Commission has made a series of frequency related reforms over the past couple of years, including the introduction of two new fast frequency response markets, to mitigate these risks.
To build on these arrangements, the AEMC has made draft rules to require scheduled bidirectional batteries to provide PFR when:
- generating energy
- charging (except when solely powering auxiliary loads)
- providing a regulation service.
The Commission’s determination seeks to balance the security benefits against any incremental costs that battery operators may face in complying with these new obligations.
Importantly, the rule would not require batteries to provide PFR when idle or at rest and providing contingency services. The Commission is of the opinion that the costs to battery operators for providing PFR in these cases could outweigh the benefits to system security.
The Commission notes that batteries capable of providing continuous PFR when at rest may choose to do so. The draft rule is not intended to preclude or restrict the provision of PFR in this case. It also reflects that batteries are already sufficiently incentivised to voluntarily provide this service.