Connecting grid-forming BESS to Australia's largest Northern power grid: technical pathways and practical realities

This paper details the integration of a large-scale Grid-Forming Battery Energy Storage System (GFM-BESS) – the Darwin-Katherine BESS (DKBESS) - into the Northern Territory's Darwin-Katherine Network (DKN). The project represents the first deployment of grid-forming technology in the Northern Territory (NT) at this scale, with a 35 MVA (45.6 MW overload) facility replacing a retiring synchronous generator at Channel Island Power Station. The BESS provides critical ancillary services including voltage and reactive power control, frequency control ancillary services (FCAS), inertia and system strength. The integration process required extensive modelling in both RMS and EMT domains and presented unique complexities due to limitations of the existing Network Technical Code. This led to negotiated performance standards and the development of novel control strategies, including Virtual Feeders, a new On-Load Tap Changer (OLTC) control method, and tuned Rate-of-Change-of-Frequency (ROCOF) relay logic. The paper provides insights into the technical pathways, modelling approaches, and the practical realities of connecting the DKBESS as a crucial pilot for grid-forming technologies in the NT, enabling the integration of IBRs and operation under low system loads by providing essential synchronous-like services. The project is undergoing its final commissioning and compliance testing in Q3 2025. The outcomes are expected to establish a precedent for future grid-forming connections in the NT and provide valuable lessons for larger interconnected grids transitioning to higher levels of renewable generation.