Rule changes, reform needed to address poor network frequency control

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Having the power system frequency poorly controlled is like driving a car on a rough road.

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The graph introducing this piece shows a density function of power system frequency for the NEM over the last few years. The range is widening which shows that the that the control of frequency is continuing to deteriorate.

On top of this, frequency is heading outside even these bounds more often, which is of even greater concern.

The electrical engineering profession has a reasonably good understanding of why the control is getting worse.

It is not because our control systems are not as good as they used to be – in many cases they are better.

It is not because our fleet of traditional generation is aging, although it is.

It is not the widespread adoption of renewable energy sources – they simply don’t yet make up enough of the generation fleet to be a significant factor.

It is the preference of baseload generation to operate at constant load and not provide frequency control – and the rules of a market which encourages baseload generation to effectively switch off their control systems by penalising them for moving away from their dispatch target.

The energy industry gets into a manifestation of the “tragedy of the commons”. No-one really wants to maintain system frequency, so it is left to those few who can’t avoid it.

Those generators that have not spent money to upgrade their control systems (to stop the automatic as designed provision of frequency control), or those which believe they can make some money on the FCAS market.

The control of frequency is localised among a few generators instead of spreading out across the entire fleet, it is akin to operating a long train with most of its wheels missing. The generators left controlling the frequency must work harder to make up for those that are doing nothing.

The market is meant to fix this situation. It is meant to place a higher value on control of frequency and thus encourage more units to provide their services. Unfortunately, it is not working as well as it should due to basic flaws in its design.

As a result, the regulation of frequency has got worse, and will continue to get worse unless something is done.

I believe we are already experiencing some of the side effects that we know poor system frequency control can have. Our ageing traditional synchronous plant is failing more often than it used to – is this just due to equipment age? Or could it be because it is operating outside of its nominal design parameters – specifically its rotational frequency – more often?

As I write these words, news of another generator failure (Loy Yang A Unit 2) has come to light, was this because of age of the plant? Was it the way it was operated that caused the failure?

Or was it the fact that the generator was constantly ramped up and down over a relatively wide frequency range the ultimate cause?

Many of us who drive cars know they break down at often the most inconvenient time. While the component that caused the failure can usually be identified the reason why it failed is often more difficult to pin down. Was a flat tyre the result of a rough road, low quality tyres, or reckless driving?

All of these could be valid reasons for the flat tyre, but knowing the tyre is flat doesn’t tell you which reason should apply.

However, we do know that any of the reasons given could be the cause and if we want our tyres to last longer it would be prudent to avoid all of them whenever practical.

Having the power system frequency poorly controlled is like driving a car on a rough road. A rough road exposes the car to jolts and sharp rocks which it doesn’t experience on the highway. Similarly, for generators, a poorly controlled frequency regime exposes them to changing mechanical vibrations and changing electrical and magnetic fields.

As a generalisation, machines do not like changes to their operating conditions – poor system frequency regulation introduces constant change across the whole NEM which is experienced by every connected generator. Is it any wonder we seem to be getting an increase in electrical equipment failures?

A group of us [1] have proposed a rule change which is a step towards addressing this issue. It removes some of the most obvious obstacles to reintroducing a regime whereby all generation plant contributes to controlling system frequency.

However, more than just a rule change is required. In fact, most of the poor frequency control practices that have become established in the electrical industry are outside the regulatory rules.

– Causer pays

– The division of the FCAS market into 8 bands (regulation raise /lower, 6 second raise /lower, 1 minute raise/lower, 5 minute raise/lower)

– The methods used to procure FCAS services

– How FCAS is allocated to generation across the system

On all these issues – the rules are silent, but procedures have been put in place to produce the complex system we currently have which often works to deliver poor outcomes.

These procedures also require reform if we are to re-establish the reliability of the power system we used to have.

All it requires is the will to do so.

[1] Peter Sokolowski, Lasantha Meegahapola, Xinghuo Yu, Jack Bryant, Bruce Miller, Kate Summers, Ryan Jennings, Mahdi Jalili, and Ryan Ghanbari.

Original article published on LinkedIn. Reproduced with permission.

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