Reliability and security are the twin foundations of the power system. Reliability is the balancing of supply and demand within network constraints, while security primarily relates to maintaining stable voltage and frequency, particularly in the sub-second periods following disturbances such as transmission faults or the sudden loss of generation.
While future reliability risks, even with demand growth, are widely considered low, there is increasing focus on ensuring emerging power system security risks are fully understood and mitigated.
Historically, thermal generators have underpinned system security through their predictable physics-driven response to disturbances, providing the fault current, inertia and system strength on which network protection and control systems rely.
As the system shifts towards technologies connected via power-electronic inverters and controlled by software, this foundation is changing.
Accountability for maintaining system security ultimately sits with energy ministers and network operators, who are understandably proceeding with caution as the system evolves.
AEMO’s 2025 Transition Plan for System Security outlines “a comprehensive plan to meet systems security requirements as well as consumer needs,” calling for investment in new system security services from synchronous condensers and advanced inverter technologies.
AEMO also highlights that system security is a shared responsibility requiring collaboration between industry, government, research, and consumer groups to bring forward solutions that those accountable can rely on.
Against this backdrop, the NSW Decarb Hub and the UNSW Energy Institute and Real Time Simulation Lab have published a white paper, Securing Power Systems in the Renewable Revolution, that examines how Australia can ensure system security as the electricity system transitions to one dominated by inverter-based resources.
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Drawing on engagement across industry, government and academia, it identifies key knowledge gaps around inverter behaviour and protection system performance during disturbances and the dynamic stability of a highly distributed, power-electronics-based grid.
It pinpoints the critical aspects that affect the power system security, highlights the need for investment in testing and validation capabilities and facilities to build confidence in emerging technologies and operating practices that underpin the billions of capital to be deployed in the coming decade.
As part of a national approach to electrification, the paper recommends an investigation into inverter responses and protection relay performance during disturbances; the delivery of a wide-area network digital twin to test actual control systems and simulate future operating scenarios ahead of deployment; and the formation of an expert working group to support policy, regulation and standards.
Over 90 per cent of new connection enquiries are now based on available inverter-based technologies. With long lead times for synchronous condensers and gas turbines, and an ageing coal fleet experiencing more frequent outages, maintaining system security during periods of low thermal generation or minimum demand will become more complex.
Greater confidence that the power system can operate securely during periods of close to 100% inverter-based supply will enable faster connection of new generation, lower costs and help meet growing electricity demand in a resilient, decarbonised system.
Mark Twidell is an Industry Professor of Practice at the UNSW Energy Institute, he is also a non-executive director of AGL
