Origin Energy’s 300MW/650MWh Mortlake battery energy storage system (BESS) has entered the Australian Energy Market Operator’s (AEMO) Market Management System (MMS), marking the facility’s transition into its formal testing and commissioning phase.
The grid-forming battery storage system, designated MLB01 in AEMO’s registry, is now undergoing low-load injection and consumption testing to verify its integration within Victoria’s transmission network, according to an update by Geoff Eldridge of consultancy Global Power Energy.
Located approximately 200km west of Melbourne at Origin’s existing Mortlake Power Station site, the facility represents one of Australia’s largest battery storage developments and a cornerstone of the company’s energy transition strategy.
The system’s entry into AEMO’s MMS follows Origin’s successful completion of unconditional connection agreements with the market operator in November 2025.
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These agreements provided the regulatory certainty required for Origin to proceed with the final construction phases, having satisfied all technical assessments and grid-impact studies necessary for safe integration with the transmission network.
The Mortlake facility incorporates grid-forming inverter technology, distinguishing it from conventional grid-following battery systems through its enhanced ability to provide system strength services.
This technology enables the battery storage system to actively stabilise the grid by mimicking the behaviour of synchronous generators, setting its own internal voltage waveform reference and operating independently of other generation sources when required.
Grid-forming capabilities have become increasingly valuable in Australia’s evolving energy landscape, where traditional synchronous generation is being progressively replaced by renewable energy sources.
The technology enables battery systems to maintain grid stability and ensure an uninterrupted power supply even during network disturbances, making them particularly suited to strengthening grids with high renewable energy penetration.
The deployment aligns with broader industry trends in the National Electricity Market, where grid-forming technology is becoming increasingly prevalent among large-scale battery storage projects.
Several other grid-forming BESS are being deployed in Australia. For instance, French independent power producer (IPP) Neoen announced last year that its 270MW/540MWh Western Downs Stage One in Queensland, which has grid-forming capabilities, started operations.
Strategic positioning and market participation
The AU$400 million (US$279 million) battery storage development, first announced by Origin in January 2024, leverages the existing transmission infrastructure at the Mortlake Power Station site.
It connects directly to AusNet’s 500kV switchyard through a dedicated substation, optimising integration costs and operational efficiency.
Construction activities commenced in August 2024, with Fluence serving as the main contractor, bringing the project into its current commissioning phase within approximately 18 months of the initial announcement.
The facility’s location places it approximately 30km northwest of the recently integrated 100MW/200MWh Terang BESS, contributing to a growing concentration of grid-scale storage assets in western Victoria.
Eldridge noted that current SCADA data monitoring indicates that the Mortlake system is progressing through systematic testing protocols designed to validate its operational parameters and grid interaction capabilities.
The commissioning process, which can be tracked through specialised industry monitoring platforms, represents the final phase before the facility’s transition to full commercial operations, targeted for completion in late 2026.
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