Who’s in charge of NEM stability and resilience?

Wind farm at sunset with transmission towers in the background (aemo report)
Image: Lucy Nicholson/Reuters

At a recent public forum, chief executives of coal-fired, renewable energy sources and a grid operator talked about their participation in the NEM in terms of their own vantage points ranging from the continued importance of coal, frustration with the regulatory environment and sanguinity with the rollout of battery-supported renewables that ‘would be just like synchronous generators’, writes Phil Kreveld.

Listening to the exchanges with each other, the question of stability and resilience of the grid arose. Questioned on these essential properties the collective, short answer was that it was an issue for AEMO rather than for them.

Their response, although to be expected, given the ‘laissez faire’ attitude practiced in the development of energy sources, grid construction and augmentation, was nevertheless concerning in that stability and resilience are all-important in realising the oft-stated aim of ‘keeping the lights on for the mums and dads of Australia’. AEMO, via its market mechanisms of reliability and emergency reserve trader (RERT) and frequency control auxiliary services (FCAS) as well as demand response, is controlling stability and resilience to the very best of its abilities, given limitations imposed by its charter.

Related article: Information system vital for the NEM

The issue is that the ‘very best of its abilities’ do not cover the millisecond scenario that the rise and rise of renewables throws up. The sinewaves shown above are typical of voltage and current and have a period of 20 milliseconds in the NEM alternating current (AC) networks. The ‘quintiplication’ of the current/voltage sinewaves in the above illustration is not just some artistic design ploy but points out an important feature of a stable network—one where, for example, the voltage sinewaves everywhere in the network maintain a fixed time relationship to one another. Sharp variation in power consumption due to the stochastic behaviour of millions of rooftop solar panels in distribution networks see to this stable relationship being broken. The same unpredictability applies to much of the large-scale renewable sources being connected at an accelerating pace. Twenty years ago, the then control procedures—basically a collection of individually attuned controls at the various generators around the South East Coast, were adequate for networks. Classical electrical engineering did the job. That is no longer possible—or rather, the only reason stability can still be maintained is because of the stabilising presence of ‘old technology’ synchronous generation.

A new stability paradigm is badly needed as the step-change in the renewables wave breaks over us. In the past, traditional generation by way of its inherent inertia, i.e., stored energy in the rotating masses of turbines and generators, provided periods of three or more seconds (three seconds amounts to 150 20-millisecond pulses) to allow slower controls to operate. In the brave new world where only renewables create electrical power, inertia will have disappeared and, therefore, control over generators and consumption centres will shrink the time to respond for their control from seconds to milliseconds.

We do not have a suitable control paradigm—it rests in the ‘too hard’ basket. Rather than addressing its implementation, solutions are sought by way of mimicking traditional synchronous generation, for example through battery storage-inverters. Does that make sense? In short, no. Battery storage is necessary for the supply of energy—to even out fluctuations in electrical power generation by wind and solar. However, there is a new reality—the very fast, millisecond response from renewable source inverters—new technology, requiring new control paradigms.

The very basis for control in renewable networks is synchronised information throughout the system of sources and centres of consumption—synchronised, because the time-relationships of voltage and current sinewaves throughout the networks must be available at all times for a control system to work at all. That is essential because of the innate fast response times of wind and solar generators. Who will invest in this control system yet to be devised but nevertheless essential? It brings the question back to the meeting of the grid operators and generator owners. “It’s not my job” is the collective response.

Related article: GenInsights21 report highlights NEM complexity and risk

In economic terms, stability and resilience are treated in the Australian electrical energy markets as ‘externalities’. As a result, investment in interconnectors and synchronous condensers, and batteries here, there, or wherever there is vacant land, is proceeding at a pace. The question of whether many of these investments could be avoided or scaled down, and whether there might there be alternate ways to assure the maintenance of stability and resilience—based on real-time analysis prior to allocating billions, does not arise.

Not grasping the nettle builds in future costs: lack of reliability and resilience will see industrial investment in standby generators and uninterruptible power supplies, will result in costs of servicing unnecessary investments and overbuilds—the much politicised ‘gold plating’, will see congestion in remote energy zone links, drive off renewable investment—and will see to it that somehow all this has to be paid for—if not by electricity consumers, then by taxpayers. The ‘externalities’ of stability and resilience will come home to roost.

In conclusion, it is inevitable that our unique national experiment with renewables cannot proceed without us recognising the urgent need to look hard at new information systems and real-time controls. We do not have a NEM mechanism for stability and resilience and this needs to be addressed urgently because we are dealing with national infrastructure essential to our economic welfare.

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