By Phil Kreveld
A recipe for dissonance? Singing a single note is not a problem. Something with lots of highs, lows and pitch changes—there’s challenge!
The Australian Energy Market Operator (AEMO) is the involuntary choirmaster, the millions of rooftop solar systems are the choir and to add spice, the sheet music varies widely amongst the choristers. That’s enough of an intro to the ‘phase locked loop’ (PLL), the operational heart of those millions of inverters connecting ‘consumer energy resources’ (CER) to Australia’s distribution networks. The PLL stands in for the ‘effective baton’ of AEMO. It is at the same time a set of handcuffs for all the distribution networks’ millions of solar inverters! They need to be connected to distribution networks to crank out electrical energy.
Related article: AGL vs Ausgrid: The pot’s calling the kettle black
At last year’s Australian Clean Energy Summit, a plenary session including Clare Savage (Australian Energy Regulator), Matthew Warren (ex Clean Energy Council) and David Leitch, energy economist, the importance of household and small business solar to the energy mix was a leading topic. Warren opined that ‘solar needs parenting’, a refence to its unconstrained growth. Recently, at a summit organised by the Australian Financial Review, Daniel Westerman of the Australian Energy Market Operator, regretted the lack of a more substantial energy contribution from the household and small business sector. This was attributed to hesitancy in participating in virtual power plant schemes.
AEMO has the task of limiting pitch (frequency) variation (keeping the ‘phase’ stable—see Fig 1) for those millions of CER inverters, all equipped with PLL so as to stay on the same beat. If frequency varies too much, the inverters shut down. To provide energy for households and businesses, and to charge their batteries, the inverters must be connected to ‘live’ distribution networks. A small number are ‘hybrid’ inverters, capable of providing energy for consumers if there is a black-out, provided they have batteries.
Aggregate CER generation capacity now matches the ‘big end of town’ generation. Therefore, things are becoming interesting—in several ways.
- One opportunity, given the big generation capacity of domestic and small business CER, is to feed excess energy into the transmission grid. That often enough turns out be a no-no to for some distribution networks and always much added capital expense.
- Another one, is for CER to band together and make distribution networks become one big generator-consumer. That is also not allowed by the Australian Energy Regulator—them’s the rules but rules can be changed! In fact, it relates to the substance of Ausgrid’s application to the AER for the installation of 130MWh battery capacity in its Mascot-Botany, and Charmhaven (north coast of NSW) distribution networks. It set off vigorous protests by AGL with accusations of anti-competitive behaviour (The Australian, Tuesday 23 September). Matt Kean, chairman of the Australian Energy Council, is not keen on this as reported by The Energy (30 October). He is reported as saying that it provides for less benefit for CER owners because it hands energy generation and sales to a monopoly.
- Or allow a bunch of brokers, to suck batteries dry, paying their owners something for the privilege—and making a motza from reducing energy demand by aggregating CER solar output when the ‘big end of town’ can’t crank out anymore energy because of their capacity limits. These are of course, the virtual power plant (VPP) schemes.
The reality is that electricity tariffs are a movable feast (for brokers) if not for energy consumers. Little wonder then that having spent several luxurious overseas holidays worth of money on their own plant (and reducing their energy bills massively), they’re wary of handing the reins to some outsider. The other reality is that VPPs notwithstanding, energy export by distribution networks is restrained in many ways. To accommodate more energy export, they have to spend big bucks upgrading transformers, on-load tap changers, re-conductoring, etc. It is therefore no wonder that dynamic operating envelopes are deployed, precisely to avoid all this.
Related article: A transition to what, when, how, and at what cost?
To conclude: Australia’s transition to renewables has illogical features, like piling on more and more large-scale generation, more and more transmission, while at the same time doing everything to make users of energy more and more independent. Standing in the way is the phase-locked loop. The PLL keeps millions of energy consumers handcuffed to an electricity system that is groaning under its weight of cumbersome regulations and ever-increasing complexity.
Isn’t time to really stop and think? Spoiling mountain habitats with wind generators, avoiding construction of solar farms on arable land by situating them at huge distances from energy consumption centres, while the solar generation capacity is right there in dense population centres. Local choirs may well be the harmonious solution for saving our planet.
