Industry experts are warning that new rules imposed on wind and solar projects are placing un-necessary costs that are forcing developers to re-assess their projects and consider taking their investment elsewhere.
The controversy focuses on the technical rules that govern engineering issues that come under the umbrella term of “system strength”, and appear to reflect great differences in how the details of the transition from synchronous machines to mostly inverter based technologies should be managed.
Like the “do no harm” rules that were imposed on wind and solar farms years ago, and then dumped because they were so badly conceived, these latest requirements – designed to replace those same “do no harm” rules – are also causing wind and solar projects to be stopped in their tracks.
It adds to the growing problems facing renewable energy projects, already dealing with the complexity of connection rules, (which has caused part of the country’s biggest wind precinct to be abandoned), the delays in new transmission projects, and the problems in supply chains and labour costs.
Bruce Miller, one of the country most respect electrical engineers, wrote a withering critique of the new requirements in a lengthy piece posted on LinkedIn on Monday, reflecting the concerns of many project developers in forensic details.
Miller is particularly critical of the interpretation by the Australian Energy Market Operator on “available fault levels” (AFL), and their impact on the grid, and the new requirement imposed on inverter-based technologies such as wind, solar and battery storage.
No physical justification
“The system strength rule effectively makes the assertion that there is some sort of inherent capacity at a specific grid location that IBR (inverter based tech) plant consumes, and traditional synchronous plant provides,” Miller writes.
“There is no physical justification whatsoever for this assertion.
“System strength is complicated. It is multifaceted, and can only be understood by studying its component parts which includes: fault level, system impedance, control system behaviour, interactions with other plant etc. a proxy measure such as AFL captures none of this.
“AFL is a fictitious metric which measures nothing of any physical consequence, but it is this measure which is the key parameter used to determine how much cost should be allocated for system strength.
“This is the main metric, which developers claim is killing off new renewable projects, and putting Australia’s energy transition program at risk.”
The former “do no harm” rules required many wind and solar projects to install their own “synchronous condensers” next to their projects at great cost. Many have never been used. See our story: Do no harm? How Australia’s regulators fumbled the transition to wind and solar
The onus was then switched away from individual project developers – after the networks themselves admitted it was doing more harm than good to the grid – and put into the hands of networks in the hopes of some co-ordination.
Wind and solar will pay the cost
But Miller and others argue that the networks are using the new interpretation to justify hundreds of millions of new investment in new synchronous condensers across their grid, ostensibly to ensure system strength requirements are met. And wind and solar farms will stay pay the costs.
Miller says the reasoning behind this investment is often a “nonsense.”
He writes: “Proxy concepts such as AFL add another layer of obfuscation to an already highly technical discussion – and we believe are not safe concepts to be used as the basis for “system strength” charges.
“We hope this will be overturned sometime in the near future when people realise the deleterious effect this concept haves on the industry.”
Miller says there are alternatives which will impose a much lower cost on developers.
“The costs estimated by TNSPs (transmission network companies) to install unnecessary synchronous condensers results in excessive costs which no project can tolerate.
“It is much easier to build overseas or for the projects themselves to take on the responsibility to provide suitable remediation of the proxy AFL metric rather than to pay excessive costs for others to provide a centralised solution.
“Any solution, centralised or project specific should address the real system reliability concerns – not rely on minimising proxy metrics which have no basis in the underlying physics, and will almost certainly lead to sub-optimal outcomes.
Contrary to the aims of the market
“Attempts by any rule to distil the various issues lumped under the term “system strength” to a one line formula will cause overinvestment in unnecessary plant or discourage private investment.
“This is contrary to the stated aims of the National Electricity objective.”
RenewEconomy understands that the views of Miller are widely shared, and that AEMO is responding to the issue by requesting its own rule change to the AEMC – which sets the rules of the market – to try and address the situation.
It’s deeply ironic, because it is believed that the costs imposed by the new rules are potentially so great that some developers have suggested they go back to building their own syncons – the very situation that the new rules were trying to avoid.
This is not the first time that new rules have been imposed on wind and solar projects in particular, and put a brake on new investment.
As Miller writes in his introduction, the problem emerges from the scale and the complexity of the transition from one technology to another. As some others have noted in the past, problems can emerge when lawyers and economists are tasked to try and solve issues best left to engineers.
Ripples in a pond
It’s worth repeating Miller’ observations here.
“Imagine the following scenario – the electricity grid which since the late nineteenth Century has used rotating generators to provide the source of its power has now changed these out for power electronics.
“What was once a system underpinned by rotating iron and copper is now increasingly being propped up by stationary silicon controlled by clever software.
“The new technologies behave well under normal conditions, however when a power system fault occurs near an installation, it may become unstable – it could start oscillating in power, voltage, and current output. This causes other nearby power sources which use power electronics to also begin to oscillate.
“Like ripples in a pond after dropping a large rock into its centre, the disturbance propagates outwards until virtually every generator on the system is now oscillating out of control.
“Protection systems may automatically operate to trip some of the generation in the hope that the oscillations will cease but this also results in a loss of supply capacity. The load/generation balance is affected and despite the operation of load shedding a system collapse ensues leading to a total blackout of the whole grid.
“This is the nightmare scenario that the rules and guidelines relating to “system strength” are aimed at preventing.
“But – how realistic really is this scenario? And assuming it is a possibility , how effective are existing rules in preventing this or similar events from happening?
“Two key questions which give interesting insights.
“There are also other issues that are often lumped in with system strength, specifically:
• Three phase fault levels
• Load shedding and generation shedding
• Regional stability
• Protection system operation
“To my mind, these issues should not be conflated with the poorly defined concept “system strength” but unfortunately this is what has happened – and like other NEM rulings and guidelines in the past it is now acting as a brake on the energy transition and causing unwarranted economic damage to many projects.”
RenewEconomy reached out to AEMO for a response but did not hear back before publication.
