Gas plants, not wind, may have been at fault in South Australia blackout | RenewEconomy

Gas plants, not wind, may have been at fault in South Australia blackout

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Sudden changes in output from ageing gas-fired generators may have worsened impact of storms in South Australia blackout, new study suggests. Inverter controlled solar, wind and storage may have ridden through the problems and kept the lights on.

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The role of ageing gas-fired generators may have been part of the problem in the events leading up to the state-wide blackout in South Australia in September, which experts say could have been avoided if the gas generators had been replaced by inverter linked renewables and storage.

A new study by international renewable energy and storage firm RES and engineering group Lloyds Register has modelled the events leading to the September 28 blackout, and suggested that if inverter controlled solar and storage had been in place instead of gas generators, then the blackout may have been avoided.


That’s because new smart and fast reacting technology can respond much quicker to unexpected events than the ageing portfolio of gas and diesel generators. The inverters and storage that go with such systems could have smoothed out the changes in output and voltage, and not made them worse as the gas-fired generators did.

It’s ironic, because the blackout in South Australia has been used by the Coalition government, the fossil fuel lobby and critics of renewable energy as proof that such technologies are not reliable and endanger the grid. The findings also challenge the idea that the situation can be resolved with more expensive transmission lines and more gas generation.

The blackout was caused when huge storms, with winds of up 260km/h, brought down three major transmission lines, in turn causing changes in output and frequency that caused the link to Victoria to separate and the grid to go “system black”.

The fall in output from six wind farms, because they were not programmed to ride through multiple voltage changes, were blamed in some quarters. However, most energy experts say the blackout was inevitable no matter what generation was operating in the state.

Questions have also been raised about why the Australian Energy Market Operator took no pre-emptive action, despite clear warnings of the approaching storm. Its latest report on the blackout is due for release on Monday.

The new study from RES and Lloyds Register suggests the problem may have been in the way that the gas-generators responded to the changes in the network. The sudden changes in output from the gas-fired generators may have made the situation worse, as they did in a previous outage in November, 2015.

Using precise computer models of the South Australian system obtained from AEMO, RES and Lloyds Register looked to see if the system may have performed any differently if the remaining gas generation in South Australia was replaced with inverter connected batteries and solar power.

This is an excerpt from their report:

“The simulation shows the behaviour of the wind generators, gas generators and interconnectors with Victoria in the lead up to the disconnection of the Heywood Interconnector. It starts at 16:17:30 AEST, approximately 45 seconds prior to disconnection of the Heywood Interconnector.

Notice the how the gas units swing up and down, causing rapid loading of the interconnection after the faults at 68 seconds and 74 sections. At the 76 second mark the system voltage collapses. The simulation is stopped at this point, as the models provided by AEMO do not include the very fast equipment protection systems that disconnected the Heywood interconnector (ref 2 p.16) at this point.

Screen Shot 2016-12-08 at 7.39.13 AM

So, would the system have behaved any differently if the gas power stations were replaced with inverter connected solar and storage power stations?

To find out, the modellers repeated the simulation  with the same fault sequence, and in this case the inverter generators smoothly resume power after the fault, flows on the interconnection remain stable and the system survives.

The “wobbles” in the output from the gas generators disappear, and the system remains stable.

lloyds south australia solar

And it should be pointed out that this occurs even with the wind farms losing output from the setting of their fault-ride through mechanisms, which in most cases have since been fixed.

What does this mean?

It shows that inverter controlled solar, wind and storage generation is offering the opportunity to provide much smarter and more stable controls than the previous combination of gas and coal-fired plants. And remember, most of South Australia’s gas plants operating on the day of the blackout are 40 years old.

“While there is much discussion around the challenges of integrating renewable power into the grid, technology is advancing at a rapid pace,” the report says.

“So perhaps a fully secure and sustainable future for electricity is not so far away.”

To illustrate their findings, RES Australia and Lloyd Register are progressing plans for a 100MW lithium-ion battery storage plant in South Australia, in a location that is yet to be revealed. They hope to use this to illustrate the savings that could be achieved from avoiding construction of more transmission lines or more gas plants.

The findings of the study – which are consistent with observations made by the likes of Reposit Power, network operator ElectraNet and even AGL (pointing to benefits of renewables based micro grids), point to the rapid change in energy systems, as dramatic as the switch from internal combustion engines to electric vehicles.

Andrew Jones, from Lloyds Register, says the gas market wobbles are the natural result of a system focusing on “inertia” and “synchronous” generation. Gas plants are like giant flywheels – if the output is blocked, it will suddenly speed up, much like a car might do if you apply the clutch and keep your foot on the accelerator.

Then it tries to back off. In each case, it overheats, leading to the sort of output “wobbles” highlighted by the AEMO data.

“Because the system was on edge, this would have helped push it over,” Jones says. “We are still waiting for data from AEMO, who have said the interconnector was “out of sync” but haven’t explained what they mean by that.”

“But what we do see here is that the inverter connected generation rides through the event.”

Jeremy Moon, from RES-Australia, adds: “There is a lot of talk about power system security. Inertia is seen as key in traditional power systems, but we think we should start to use the battery storage system and want to get that conversation started.”

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  1. riley222 4 years ago

    Makes a lot of sense and points to a logical path forward.
    Then I remember seeing ‘end of days’ Bernardi and the crazed look on his face as he talked about Turnbull’s toe in the water review. OZ is stuffed under this dysfunctional rabble, there seems zero chance of any compromise with ratbags like that. ‘My way or the highway’ it is with the aim of stopping and eliminating renewable energy .
    Next they’ll want out of the Paris accord, Trump will provide the impetus and Bernardi and his ilk will be all over it, with of course plenty of post truth support from sections of the media.

    • trackdaze 4 years ago

      Cory bananas has already suggested walking away from paris. Not many would have heard over the hysterics.

    • Bristolboy 4 years ago

      In my opinion basic economics will ensure that the switch away from fossil will continue to happen globally, even if there are short-term political bumps in specific countries.

  2. Kevin Brown 4 years ago

    And what about the gas and diesel plants who failed to to provide power to restart the grid as they were contracted to do? How much longer did the “system black” outage ? What penalties have they incurred for failing to meet thir contractual obligations?

  3. Chris Fraser 4 years ago

    Goodbye inertial, synchronous generation !

  4. Cooma Doug 4 years ago

    “The interconnector out of sync” happens if the system frequency in SA could not keep up. The two states slip out of sync and cause the interconnecter to trip. The gas gens go nuts when the major lines hit the ground causing voltage collapse. This disrupts the balance of input and output of the gens. No dossil fuel gen could have stayed on line.
    The high tech renewable solution is real.

  5. John McKeon 4 years ago

    Whilst I admit that I am not at all up to speed on the engineering technicalities of the whole SA electricity generation & transmission scene, may I submit the following rhetorical question:

    Was it not at least half obvious what an opportunistic stance was been taken by Malcolm TurnbullS and his COALition to knock sustainable energy innovation – when that storm and blackout struck? [And not that word: innovation!!! Sound familiar?]

    On the subject of climate change and our extremely disappointing prime minister, Robert Mann has an written a stinging critique at:

    [Declaration: 1) I admit I don’t vote LNP anyway. 2) I’m not promoting a magazine – I genuinely think that Robert Mann’s article is a very trenchant political analysis of Turnbull’s leadership re climate change. He is easily as disappointing as Rudd when it comes to changing his tune on this profoundly important issue.]

  6. permaculture utopia 4 years ago

    Anyone who owns a hybrid or off-grid inverter knows the inverter can ramp it’s output up and down at near instantaneous speed. Mine does this while maintaining a near perfect 230VAC +/- 2% and 50Hz +/- 0.1% waveform. No fossil fuel generator can do that. Additionally, if a fossil fuel generator is connected to supply additional power in winter or during cloudy weather, the inverter will also compensate for changes in the load so the fossil fuel generator can be run at a constant speed within its optimal efficiency range. In this way, the inverter acts as the FCAS service for the off-grid property. The inverter can make fast changes in output power because the electrons from the battery are very fast. It can do this because the electrons have less mass and inertia than a gas or coal turbine. In other words, the inverter offers the only true 50Hz synchronous output because no other generator can perform at a specification of +/- 0.1% tolerance of waveform quality.

  7. john 4 years ago

    When your political stance is 1,2,3
    Point 1 Renewable energy is bad.
    Point 2 Renewable energy causes all problems.
    Point 3 Only the present system is the best.
    Of course each and every problem is because of point 1 or 2.

    I bet you with out a fear of failure in my bet that the Chief Scientist will recommend tomorrow Friday that Australia implements Renewable Energy as soon as possible because the outcome will be a lowering in final energy cost to the consumer.

    I will be extremely surprised if the Chief Scientist does not go along those lines.

    I also expect that his recommendations will be ignored and written off as ivory tower pontificates that do not resonate with the ordinary person.

    Translation This will be dismissed because insert here ” ” said so and I want to watch next idiot show on 3rd rate TV.
    Sorry for being so obnoxious but honestly that is my expected outcome.

    • Joffan 4 years ago

      When your value system says that renewable energy is awesome, and never causes any problems, then of course any problems “must” be caused by something else, not the cranky turn-up-when-it-feels-like nature of weather-based systems.

      The disingenuity of describing the infeasible battery backup as “solar battery” is just another attempt to hitch a ride on this faith.

      • Chris Fraser 4 years ago

        No – all the problems are caused by politicians, not modern technology.

        • Joffan 4 years ago

          Without politicians, there would be no subsidies for renewables, no priority grid access, no market share targets, no carbon taxes… actually there’d be almost no renewables, so you’re probably right that the politicians caused these problems.

          And I don’t reject renewable energy, but I do object to the dewey-eyed mindset that attributes any issues to some other system that doesn’t sufficiently accommodate its foibles.

          • Chris Fraser 4 years ago

            Excellent ! Then you acknowledge the fact that without politicians, the influence of science on climate responses and the Infrastructure would be exactly as it should be. Without politicians, you acknowledge new technologies dovetail immediately into small “L” and capital “L” liberal ideologies of market responses. Without politicians, you acknowledge the artificial subsidies they created in favour of fossil fuel energy no longer exist.

          • Joffan 4 years ago

            I don’t understand what your point is, or indeed most of what you are saying.

            You may have misread my previous comment as lamenting the existence of politicians, which was not my intent. I do not endorse or accept the fantasy that uncontrolled market forces will result in a better world.

          • DJR96 4 years ago

            The “other system” being the existing 20th century tech NEM.
            And no, it does not sufficiently accommodate renewable generation tech. It simply wasn’t designed to. The renewables we have now are a scarcely tolerated nuisance as far as the NEM is concerned.
            It is very clearly the NEM design and operating model that needs to be reformed, dragged screaming and kicking into the 21st century. All the required technology is there already, it just needs the NEM to embrace it and adapt for it.
            Until the NEM, the entire industry and politicians acknowledge this, there will never be a happy ending.

  8. permaculture utopia 4 years ago

    A renewable energy grid will also not need Demand Response Management (DRM) strategies, as the graph demonstrates how the inverter can supply a load from batteries while accurately matching rapid spikes or troughs in the load without effecting the voltage or frequency. While fossil fuel generators remain on the grid they can run at their optimum efficiency, while inverter/chargers working with batteries can accurately match the load.

  9. permaculture utopia 4 years ago

    This article also highlights how private industry is leading the way with a renewed focus upon utility level storage, to enhance grid reliability and dispel myths, enabling the country to unequivocally move forward with renewable energy. It is a shame ARENA didn’t tap this opportunity before all the SA outages, by funding the Lyon PV/storage projects as I lobbied for. SA appears the crisis we had to have, for leaders to focus first and foremost upon proof of concept with an effective prototype of a utility level grid, duplicating what renewable energy has already achieved decades ago with microgrids and off grid installs, where no additional FCAS has ever been needed.

  10. permaculture utopia 4 years ago

    A hybrid or off-grid inverter can ramp it’s output up and down at near instantaneous speed. Mine does this while maintaining a near perfect 230VAC +/- 2% and 50Hz +/- 0.1% waveform. No fossil fuel generator can do that. Additionally, if a fossil fuel generator is connected to supply additional power in winter or during cloudy weather, the inverter will also compensate for changes in the load, so the fossil fuel generator can be run at a constant speed within its optimal efficiency and power output (also saving fuel). In this way, the inverter acts as the FCAS service for the off-grid property. The inverter can make fast changes in output power because the electrons from the battery are very fast. It can do this because the electrons have less mass and inertia than a gas or coal turbine. In other words, the inverter offers the only true synchronous output because no other generator can perform at a specification of 50Hz +/- 0.1% tolerance of waveform quality.

    • solarguy 4 years ago

      Go to the top of the class son and pick up a gold star!

    • DJR96 4 years ago

      Spot on.
      Your accurate description explains that the whole notion of “inertia” as being an essential characteristic can be thrown out the window. Inertia was exactly the problem.
      This is the very point that the industry must comprehend and reform towards.

      • Nick 4 years ago

        Exactly wrong. Inertia caused no problems.

        • DJR96 4 years ago

          For the SA black system event, the problem is that there was a big difference in inertia between SA and Victoria. So when there was a disturbance they don’t react at the same rate. The SA generators slowed down more than the Victorian ones. This difference creates a struggle across the inter-connector, resulting an overload that tripped it.
          Had the amount of inertia been more closely matched, they would have responded equally and not lost synchronous control.

          • Nick 4 years ago

            No, they lost synchronism across Heywood because they exceeded the maximum power transfer capability. Power flows by the equation P=V1V2/X * sin(theta).

            SA tried pulling from Victoria a power P that resulted in being unable to solve that equation for the impedance X of the line while holding voltages at the two ends of the line V1 and V2 to nominal voltage. There was no angle X that solved the equation. Inertia had nothing to do with it.

          • DJR96 4 years ago

            Nick, the two regions became out of sync BEFORE the inter-connector tripped.
            They were in sync up to when the Davenport-Mt.Lock transmission line tripped. That caused a disturbance (and urgently needed load shed) that could have been recovered from (note that from the previous disturbance it took 4-5 seconds to recover). But just one second later an attempt to re-close that line was made, re-introducing a large load (another disturbance in itself) before the system had recovered. It was at this point SA became out of sync with Vic, and another second later Heywood tripped.
            I maintain that had there been a similar amount of inertia in both states, the disturbances would not have caused the loss of synchronous control.
            Perhaps another way to describe it is that the SA generators were so far out of sync that they were effectively a lagging load on the Victorian generators.

            Now please re-arrange the equation such that you have three voltage/phase angle groups. You need one for the load on one side, you need one for the Vic generator on the opposite side using the same phase angle, then you need a third on the same side as the load with a significantly different phase angle to represent it lagging. Do that and I believe you will see a larger P between the two sides.

            I believe you will find the greater the difference in angle the greater P will be.
            Being out of sync introduces an extra load above and beyond the demand beforehand.

          • Nick 4 years ago

            Do you have a source on the Davenport-Mt. Lock trip dropping load and the reclosing picking load back up? Davenport-Mt. Lock tripped and after attempting to reclose it, the line stayed out of service at 16:18:14 per the AEMO update report (Table 3, page 18). This was about 1.5 seconds before the collapse, and the voltage and frequency plots on pages 15 and 16 of the update report show the voltage and frequency stable until 16:18:15 when the “Group B” wind turbines tripped (page 24).

            “I maintain that had there been a similar amount of inertia in both states, the disturbances would not have caused the loss of synchronous control.”

            I really don’t know what you mean by this. There was more load than generation, and the high flow across Heywood was more than the line could handle. How would increased inertia have changed this?

            “You need one for the load on one side, you need one for the Vic generator on the opposite side using the same phase angle, then you need a third on the same side as the load with a significantly different phase angle to represent it lagging.”

            I don’t follow you. It’s a single equation for the power transfer. The angle theta is the angle across the line.

          • DJR96 4 years ago

            To your first question. If a line trips the load it was carrying at the time is dropped/shed. Re-closing the line is adding the load serviced by that line.

            Figure 2, p16 of that report. At 16:18:14 the frequency varies due to the disturbance created by the Davenport-Mt.Lock transmission line. Notice how the blue line (SA side) varies by about 2.5 times more than the red line (Vic side). That difference in variation is due to the large difference in available inertia at the time. If the inertia was the same both sides, the two lines would have stayed together, varying by the same amount.

            Then during that 1.5 seconds after, it didn’t quite fully synchronise properly again. It needs about 4-5 seconds to do that.
            But before it could, even more load is put on the inter-connector when more wind turbines drop off. At which point the frequency deviates between states dramatically. Which is loss of synchronous control. For a brief moment, 0.7 seconds, the load on the inter-connector spikes, until Heywood trips.

            Sorry I’m not explaining this clearly enough. Not the easiest thing to explain.

            A graph of the phase angle of each state would be useful, but I’ll try and make do.

            Let’s work from the point at 16:18:15.1 (the moment the wind turbines drop off and frequency between states start to vary dramatically. Let’s use easy numbers and say the Victorian side maintained 50 Hz. 0.7 seconds later it did 35 cycles. And the SA side dropped to 49.5Hz. Doesn’t sound like much difference, but after the same 0.7 seconds, it only does 34.65 cycles. That’s 0.35 of a cycle or 120 degrees shift out of phase with the Victorian side. (It could be worse than this because the deviation was higher, but it wasn’t linear so it makes it too difficult work out perfectly, but it should be enough to make my point).
            Now, SA was providing 330MW from it’s synchronous generators at the time. Can I now ask you to perform the math to work out the difference in current that is?
            And that difference is an extra load on the inter-connector. If it had become a full 180 degrees out of phase, completely opposite from the Victorian side, then the full 330MW would be working against the Victorian side, ie. an extra 330MW load to carry. That is the devastation of losing synchronous control!

            Hope that helps.

          • riley222 4 years ago

            Hey Boys, as a general reply , would it be safe to say the answer is there if the will to look for it is there ?

          • Nick 4 years ago

            It’s safe to say the AEMO reports state all the facts about the science of the blackout. There’s nothing missing from their reports from the science side.

            Unaddressed is things like why didn’t they know about the finite number of low voltage events before the turbines trip? Or why they didn’t schedule frequency regulation in SA during a serious storm.

          • riley222 4 years ago

            I thought the federal government was pretty quick out of the blocks when this happened, almost like such an event was expected and here was the chance they’d being waiting for to monster renewables, especially wind.
            It’s probably the reason as little will be done to fix it as they can get away with, hoping the public believe their spiel that renewables are not grid compatible. All part of an overall plan to slow the introduction of renewables into the grid by any means available.

          • Nick 4 years ago

            “If a line trips the load it was carrying at the time is dropped/shed. Re-closing the line is adding the load serviced by that line.”

            Nope. Load is dropped only if the line is radial, and Davenport was not radial from Mt. Lock at the time of the trip. When the line opened, the load was served by the intact parallel path. So when the line reclosed, it didn’t pick up any load because that load was continuously connected.

          • DJR96 4 years ago

            Ah, I understand what you are saying.
            However, in this case the parallel line (or loop) is the Davenport-Belalie line, which happens to be on the same towers and had tripped out just 8 seconds beforehand.
            So when the Davenport-Mt.Lock line tripped, all the load it was carrying at the time had no other line to carry it. So it was load lost.

          • DJR96 4 years ago

            Sorry Nick, you’re correct.

            The Davenport-Mt.Lock transmission line was the third line supplying Davenport to fail. There was a fourth line that was still providing power there.

            I’ve edited my previous post to reflect that. Hope that’s better now.

  11. permaculture utopia 4 years ago

    This article highlights how private industry is leading the way with a renewed focus upon utility level storage, to enhance grid reliability and dispel myths, enabling the country to unequivocally move forward with renewable energy. SA appears the crisis we had to have, for leaders to focus first and foremost upon proof of concept with an effective prototype of a utility level grid, duplicating what renewable energy has already achieved decades ago with microgrids and off grid installs, where no additional FCAS has ever been needed. It is important to address fears in public and political sentiment by consolidating a paradigm, instead of focusing only upon more renewable energy generation. This is what happens when technology is attempted to be marshalled as a driver, when awareness has always been the driver and maker of new paradigms and new epochs in history. Collective awareness is the driver and what votes. From a social science perspective, that’s what primarily needs to be addressed.

    • riley222 4 years ago

      Whilst what you say is true, as things stand the majority of voters are supportive of moves to renewables, many voting by installing their own systems. I don’t think the problem lies with public awareness or sentiment.
      The problem is in the business/political arena, where a powerful minority have hijacked any move to enhance collective awareness, and they are attempting to force their will by a program of targeted misinformation.
      Think ‘Pizzagate’ but in the renewable arena, this is what Oz is facing right now. This is what needs to be countered, not any perceived fears in public sentiment.

      • permaculture utopia 4 years ago

        Structural hegemony exists whilst the gravity of voters has yet to reach it’s tipping point.

  12. Chris Baker 4 years ago

    This analysis doesn’t make sense to me. The second chart shows the system still running at 1500 MW after all the faults, and of that about 900 MW being supplied by the interconnector. According to AEMO report of the outage the capacity of the interconnector is 600 MW, and when it reached 850 to 900 MW in the actual event it tripped to protect the interconnector. In this model it assumes that the interconnector can supply 900 MW and remain stable. The modelling seems to focus on swings of the gas units, and somehow attributes these swings to overloading the interconnector. Surely the interconnector is overloaded because the wind farms shut down, not because the gas generator output fluctuated. The interconnector did actually pick up the load, and for about 0.8 seconds if I am reading the AEMO report correctly. By then the protection equipment acted as it should and tripped the interconnector.

    In this modelling, substituting inverters for gas generators, the interconnector still has to pick up the missing 300+ MW of generation, and surely the protection equipment would still shut it down because its running at well over its capacity.

    I wonder at the rationale of using batteries and inverters in the manner suggested in this modelling — that is, as a substitute for base load gas generators. To supply continous power at 330 MW (the gas generation at the time) requires a huge battery capacity, and to supply this load, say overnight, would need many gigawatthours of capacity. That is a very large battery.

    Its interesting to speculate further, that if such a battery/inverter installation, capable of 330 MW or generation capacity, was to be on standby, rather than running as baseload generation, it could have picked up the load as the wind farms tripped, and the interconnector would not have been overloaded. The inverters would only have had to carry the load long enough for the wind farms to be reset or additional gas generating units brought on line — requiring a much smaller battery installation, probably measured in hundreds of megawatthours (still a big battery). This seems to me a more likely use for this technology rather than as base load power.

    • permaculture utopia 4 years ago

      Yes initially inverters/storage could be on standby or merely act to smooth out rapid spikes or troughs in the load, due to their much more rapid ramp of the output power without compromising the voltage or frequency. And, having established the superiority of the paradigm in terms of its inherent stability and flexibility, it can be rolled out across the whole grid, including utility level applications, and energy harvest much closer to its point-of-use.

    • Nick 4 years ago

      Agreed. The study here started with a conclusion and then tried to sell a story that fit that conclusion. It may convince people who like the story but won’t influence policy makers.

    • taiyoo 4 years ago

      How long would it take for the wind and gas to reset?
      Seconds or minutes? 330MW for 5 minutes (the longest frequency service AEMO feels the need to procure) is only 27.5MWh.

      • Chris Baker 4 years ago

        In this case the gas generators are running at about full capacity, and its not a question of restart, but starting other idle generators from cold. And maybe not at the plants that are running, because I think they are base load and probably slow to start. Perhaps quarantine peaking plant can start quickly from cold. I’d like to think that the wind farms could restart very quickly because its just a controller issue and not a physical limitation that shut them down in the first place. Maybe its minutes and just needs an operator to initiate restart. It would be interesting to hear from someone who knows…

        • DJR96 4 years ago

          You’re pretty much right here.
          Gas peakers need about 10-15 minutes to get online.
          During that SA black system event, Ladbroke’s gas was already running at full capacity so it couldn’t help any further. But Torrens Island had 3 of its 4 turbines running. And they were only running at just over 50%. But being steam turbines it would take a bit longer to ramp up. Did they? Good question…..
          Don’t forget the Murraylink HVDC either. It was only running at half capacity at the time too. It could have stepped up almost instantaneously. Was it instructed to? Another good question……

    • Vindaloo Bugaboo 4 years ago

      Surely the interconnector is overloaded because the wind farms shut down, not because the gas generator output fluctuated.

      Bingo. Smart people can see through this smoke screen from RES (who has a conflict of interest). You are one of them.

  13. Nick 4 years ago

    Giles, why do you keep pushing phony pieces like this and ignoring the real story: that while wind did trip off that day, the issue was identified in a day or two and fixed in a week or two at a cost of $0. Your continued insistence that something else must have caused the blackout is just embarrassing.

    • permaculture utopia 4 years ago

      The point remains that inverter controlled battery storage provides the fastest response times in potentially cascading system failure. Severe weather has created increasing challenges to energy security. Inverter controlled storage is the only technology capable of responding swiftly in crisis. Mechanical generators have inertia.

    • DJR96 4 years ago

      The report is pretty much correct. It may not have actually understood the exact issue or described it clearly though.
      Please read the report I posted further down. I think I may have described it in a way that’s easier to understand.

  14. GiveADogABone 4 years ago

    ‘The simulation is stopped at this point, as the models provided by AEMO do not include the very fast equipment protection systems that disconnected the Heywood interconnector (ref 2 p.16) at this point.’
    Fig 1.
    Interconnector power at 850Mw at trip. Normal maximum load 650Mw.

    ‘The “wobbles” in the output from the gas generators disappear, and the system remains stable.’
    Fig 2.
    Q: After the event, interconnector power is ?
    A: Greater than 650Mw and 850Mw. This simulation should have stopped at interconnector load greater than 650Mw with a disconnected Heywood interconnector.

    ‘What does this mean?’
    Fig 2. makes a false assumption and fails to heed the warning in Fig 1. – ‘Model stopped as it does not contain interconnection protection’. In reality, Fig 2. trips as well.

    Chris Baker makes the same point in his own way further down the thread.

  15. GiveADogABone 4 years ago

    To understand the blackout, you have to understand :
    Power Grid – Cascade Failure and Spinning Reserve :

    Key Phrases :
    A cascading failure is a failure in a system of interconnected parts in which the failure of a part can trigger the failure of successive parts.
    A power outage (also called a power cut, a power blackout, power failure or a blackout) is a short- or long-term loss of the electric power to an area.
    In electricity networks, the operating reserve is the generating capacity available to the system operator within a short interval of time to meet demand in case a generator goes down or there is another disruption to the supply.

    Cascade Events :
    On the evidence currently available, the cascade failure on 28th September 2016 followed this sequence :-
    1: a storm which …
    2: contained tornadoes which …
    3: caused voltage distrubances on and/or damage to grid circuits which …
    4: caused wind turbines to trip which ..
    5: caused the Heywood interconnector to trip on overload which …
    6: caused a high RoCoF event on the disconnected SA grid which …
    7: caused the UFLS in SA to fail to operate which …
    8: caused all connected generation in SA to trip at 47Hz falling which …
    9: caused a blackout throughout SA.

    From 2: to 9: is a cascade failure. All of 2: to 8: are the cause of 9:. If any one of 2: to 8: had not happened, then neither would 9: have happened. Arguing about whether or not it was the pylons or the wind turbines that caused the blackout is fatuous. The real system failures were in 5:, 6: and 7:.

    5: Failure to carry sufficient spinning reserve on the interconnector was operator error.
    6: and 7: Failure to realise that an interconnector trip from 850Mw would cause a high RoCoF event (which caused a UFLS non-event) was an operator error.

    Q: Was the blackout(9:) caused by the :-
    8: all generation trip at 47Hz, or
    7: failure of the UFLS to actuate, or
    6: low system inertia causing a high RocoF event, or
    5: Heywood interconnector trip, or
    4: wind turbines tripping, or
    3: voltage disturbances , or
    2: tornadoes.
    A: All of the above
    1: to 4: are to be expected and should be survivable, even with a degraded grid. The first real system failure is 5:.

    Throughout this event the spinning reserve in SA should be accounted.
    1: Prior to the event, no FCAS services were commissioned by AEMO, so spinning reserve in SA was zero, apart from some inertia. The main spinning reserve was therefore provided by the Heywood interconnector.

    2: Prior to the event, the load shedding system (UFLS) in SA was armed but in the event totally ineffective. It was defeated by the high RoCof event.

    3: Therefore prior to the event there was no spinning reserve and/or UFLS in SA. It was all on the Heywood interconnector (max normal load 650Mw ), so the loss of generation (445Mw) was added to the 570Mw, resulting in 5:

    • Nick 4 years ago

      Why do you see 4 as more survivable, more “normal” than 5?

      • GiveADogABone 4 years ago

        First, 200Mw of generation tripped.
        What happened to the interconnector load?
        It rose by 200Mw because no FCAS services were available in SA.
        So far perfectly normal.

        Second, a further 200Mw of generation tripped about six seconds later.
        What happened to the interconnector load?
        It tried to rise by another 200Mw and reached the interconnector trip level.

        Third, at the time of the interconnector trip, the interconnector was the largest generator on the system at 850Mw (about 45% of total demand). The opening of the interconnector now allowed detection of falling frequency, but the loss of 45% of supply produced a RoCoF that beat the UFLS. At the point the interconnector opened, a blackout was a certainty.

        In a normal grid system, the first 200Mw trip would have been absorbed by ‘spinning reserve’ in SA. The second 200Mw trip might have challenged the UFLS with a falling grid frequency and called up an automated 200Mw load shed while generation picked up and the lost load could be reconnected. That much (i.e. 4:) is all normal and within design. A blackout caused by 5: most certainly is not normal.

        • Nick 4 years ago

          The trip of Heywood shouldn’t have caused the blackout, yes, and it wouldn’t have if the wind had been online. It also wouldn’t have tripped if the wind had been online.

          Take a look at the AEMO report from 28 September. Figure 1 on page 15 shows the voltages collapsing before Heywood opens. This is a system that is already collapsing before Heywood opens. The trip of Heywood is a reaction to the collapsing SA system, not the initiator.

    • DJR96 4 years ago

      Pretty good analysis, but there is a major omission.
      Each time there is a significant disturbance like when transmission lines tripped out due to faults, it challenges the generators. They have to adjust there outputs. During which time they must also remain synchronised to each other.
      The “wobbles” in gas generation is that adjustment but much more seriously it is also a struggle to remain synchronised with the line from Victoria. The opposing generators really fight each other and place much greater loads on the interconnecter. That is the wavy line seen in figure 2 of the first report from AEMO.
      So in your analysis you need a point 4.5 – interconnecter overloaded due to loss of synchronous control.
      Had that not happened, 5 onwards may have been prevented.
      See my report below for full run down.

  16. permaculture utopia 4 years ago

    The central challenge of severe weather events is the need for a fast response during potentially cascading system failure. Mechanical generators are too slow for this purpose. Inverters and batteries have no moving parts and can ramp up their output power in milliseconds. Inverters and batteries have always been the basis for the Uninterruptible Power Supply (UPS). Works on my property. Will work when strategically located in regions in grids.

    • Nick 4 years ago

      The central challenge is avoiding cascading collapse to begin with.

      Mechanical inertia is a good thing in most systems, basically any time other than a system collapsing. You’ll find converter backed generation (wind, solar, batteries) increasingly mimicking mechanical inertia because it’s a good thing.

      • permaculture utopia 4 years ago

        No inertia is not a good thing. Lightning is fast. The response needs to be equally fast. A generator with inertia is clearly not needed on my property so how is it needed at every other level of scale? The only limit is the amount of storage and the peak power output of the inverter. The inverter will produce its peak power 50Hz +/- 0.1% regardless of whether it is ramping its output up or down quickly.

        • Nick 4 years ago

          Because unlike your property, generation across the entire system needs to work together. That’s true whether it’s wind, solar or gas. They’re all synchronous. Without inertia, a lightning strike will cause all of them to lose track of where in the 50 Hz sinusoid they are. Mechanical inertia provides that for a gas unit, and batteries and other asynchronous units will mimic that inertia. Because it’s so vital.

          If you feel inertia is so bad, why do grids not collapse every time there’s a lightning strike?

          Unfortunately, your house is a poor proxy for how a large interconnected power system functions.

          What you’re calling for is actually infinite inertia, not zero inertia. You’re advocating for inertia.

          • permaculture utopia 4 years ago

            No the inverter is the only true synchronous generator. For example, my inverter has a grid interaction profile where it can stand alone and only access the grid to top up its peak power output. To do this, the inverter must count the beat of the 50Hz of the grid, then dance in so fast, that the inverter uses this transfer ability to seamlessly add to its own peak power output. In other words, the inverter is so fast, it can synchronise with the grid and ramp its output power so fast, it can accurately match the load. No inertia needed. The only reason fossil fuel people harp on about inertia, is inertia was a clumsy fuel inefficient way to ensure stability of frequency with mass, when electricity presents rapidly changing loads. The inverter and battery are electrical not mechanical. My inverter synchronises in milliseconds with the larger grid it is in. No fossil fuel generator can do that.

          • solarguy 4 years ago

            Sounds reasonable to me.

          • permaculture utopia 4 years ago

            Yes so the fossil fuel generators can continue to run in the background where needed, and allow newer rapid response technology to manage peaks and troughs in demand. In terms of rapid response, the order appears to be inverters (milliseconds), hydro (seconds), gas (hours) and coal (days).

          • Chris Baker 4 years ago

            PU I suggest you left out perhaps what is currently the most important rapid response energy source. That is inertia. It also responds in milliseconds to the change in demand. If extra power is needed from a spinning generator it is taken instantly and as a result of this the frequency drops. Its in response to this frequency change that the governors begin to open on the steam and hydro plants to take up this power demand in a more sustainable manner.
            Maybe we could begin to think of inertia like a battery. It is a source of energy that is instantly available, and like a battery, needs to recharged again, by bringing its frequency back up.

          • permaculture utopia 4 years ago

            Yes I largely agree the inertia of spinning reserve functions like a battery, although spinning reserve costs millions of dollars a year to keep it spinning in case, using fuel, while when in standby a battery just sits there.

          • Chris Baker 4 years ago

            there’s a difference between spinning reserve and inertia. Inertia is there for free in every spinning generator and is ready to instantaneously take the load and does so continuously allowing the governors the seconds they need to pick up the load. Spinning reserve picks up the load after it has first been picked up by inertia. The system becomes aware of the extra load because the frequency drops to an extent that triggers a need for spinning reserve to respond.
            I agree that it batteries will play a role in replacing spinning reserve, and at some suitable price that will make it worthwhile for you to set aside battery capacity just to be ready to take up the load. Its in this area we see so much angst between the regulator and market players to find a suitable pricing mechanism. Changing to 6 minute payment intervals I’m sure would help.

          • DJR96 4 years ago

            Yes “inertia” is a form of reserve energy. But it can not be used without the side effect of the frequency being altered. Furthermore, the governing mechanisms only respond to a change in frequency. So in fact the inertia introduces a delay in governor response, but does smooth out variation in frequency.

            The point PU is trying to make, is that with suitable battery storage available, an inverter can respond instantaneously to changes load demands, and it can do it whilst maintaining frequency and voltage very accurately.

            The battery storage doesn’t have to be a lot of MWh either, it at the least only needs to hold long enough for generation to respond. Even one minute is extremely useful.

          • permaculture utopia 4 years ago

            Thanks for the dancing in analogy. I got that from your previous posts.

          • Nick 4 years ago

            The inverter is simply following the grid.

            “Synchronous generator” is a term that means something. It means the speed of the prime mover directly relates to the electrical frequency.

            The inertia of the system is what allows your inverter to “dance” in sync with it. If the system was too weak, the connection of a source would push the system around and be unable to sync. This is sort of what was happening during the blackout, when South Australia was pulling too much power across the Heywood Interconnector. The SA end of the line was too weak due to the wind turbine trips, causing power oscillations and collapsing voltage.

            There’s no way to ensure a stable grid without inertia. That isn’t an antiquated sentiment, it’s a fact. Without system inertia, your inverter couldn’t “dance” with the grid. Without inertia, an increase in wind output would cause a wind generator to slip out of synchronism with the rest of the grid. Inertia is what holds it all together, whether it’s wind or gas or anything else. Your misunderstanding of the fundamental physics of the power grid does not change this.

          • Chris Baker 4 years ago

            I think its worth expanding more on Nick’s comments about inertia and that your house, Permaculture Utopia, is not a good analogue for the national grid.

            Its easy to think of inertia as something bad like the inertia of the Luddites of the coalition holding back progress. This is a kind of inertia. In the electricity system though inertia is a good thing, and endows synchronous generators with an ability to handle overload conditions.

            Think of a steam turbine, such as at Torrens Island running at half power. Its mechanical inertia means though that in the event of other generating units in the system tripping it can instantly pick up some of that load and momentarily generate more power, which is what we see in the graphs and described pejoratively as wobbles. Lets say hypothetically it increases from 80 to 100 MW momentarily. Because its steam turbine is producing only the power it need before the event, 80 MW, it begins to immediately slow down because its pulling the extra power from the inertia of the spinning mass. As the frequency begins to drop the governor opens and attempts to supply more steam. But for a moment it and all the intertial generators in the system, including those in Victoria, will pick up the extra load by taking this power out of the spinning mass in all those units combined. This gives some time for the governors to begin to open and supply more steam or water power to meet the new demand.

            The non-inertial generators in the system, such as the wind generators and the grid connected inverters are already at maximum and have no ability to feed in extra power for an event such as this. They don’t wobble because they don’t even try to help maintain the system. As you say they synchronise perfectly with the grid and so slavishly do they do this that they go down with it, offering no support to the collapsing frequency.

            A suggested solution to this problem is to program into these devices synthetic inertia, so that they too can offer system support. This requires that they either normally run below capacity in the case of an solar inverter, or momentarily overload the spinning blades in the case of wind turbines, and extract energy from the inertia in them.

            Inertia in the national grid could be usefully described as instantaneous reserve capacity. In the seconds while it is being extracted the controllers on the spinning reserve have a chance to respond to pick up this load in a manner that can be maintained.

          • permaculture utopia 4 years ago

            “The non-inertial generators in the system, such as the wind generators and the grid connected inverters are already at maximum”.

            The topic is not grid-connected inverters or wind turbine driven inverters. The article is about inverter controlled batteries. Inertia is not needed in an electrical system able to ramp up and down at almost instantaneous speed. We’re talking about RE like wind and solar first being fed into a battery, then the inverter firing up and dragging current from the battery when needed.

          • DJR96 4 years ago

            Just a little on your last 3 paragraphs .

            As of October there was a change in AS4777. It requires all new inverter systems larger than 3kW per phase to have reactive power control RPC. What this means is that if it senses the grid voltage or frequency is lower than it should be it will feed-in reactive power. The AC waveform it generates will be slightly ahead of the grid. Leading. This supports the grid, helping it get back to the 50Hz and in the right voltage range. (220-253V) If the grid goes over 253V it should start lagging, putting a reactive load on the grid to try and slow it down a bit. It’s not an easy feature to explain.

            This will prove to be an invaluable and essential feature moving into the future. However, the parameters programmed into the inverters are fairly wide still. Meaning the grid has to drop to 220V before RPC starts taking effect. I think in time they’ll realise it can be narrowed down quite a bit and increase it’s usefulness. No longer are inverters pure following slaves.

            So in SA, if the wind turbines are programmed to perform RPC, it would provide a huge support in maintaining grid parameters. It would be very worthwhile retro-fitting/reprogramming this into the existing wind turbines even though they pre-date the new standard.

          • Chris Baker 4 years ago

            Thats interesting and thanks for the heads up. I struggle to properly understand reactive power. Does it actually put in any more power? In this case because we’ve lost a power source we need to find some power from somewhere. Would the RPC help here, or does it only help if the voltage is out of range due to power factor?

          • DJR96 4 years ago

            It’s not an easy thing to describe and it is stretching my knowledge too. I’ll have a go but if someone else can do better, I’ll be only too happy to learn too.

            Active power is the energy that does useful work for us. Ordinary resistive loads like a heating element or incandescent globe use active power. They have no effect other than to draw current from the source.
            Electric motors and other appliances that use or form any magnetic field tend to create harmonics or noise on the supply lines. I guess the term is because it is reacting with the supply. In effect they cause a shift in the phase angle. This is where the term power factor comes into it. You may have heard of “0.9 lagging” or “0.95 leading”. This is a measure of how far the phase angle is away from where it should be. It’s generally not something most households have to worry about. But industrial customers with lots of electric motors it can add up and have negative effects on the supply. It also means it draws more power from the grid and is not detected by a normal kWh meter. Which is why commercial customers now need to have kVA meters instead because they do measure it. There is various ways to mitigate it. I think capacitor banks use correct it.

            So the new inverters can detect how much of this reactive power is in the grid and can time the feeding in of energy to counteract it somewhat. Very clever stuff, and beneficial to the grid and overall supply.
            SMA inverters now feature it and it’s on their website. I guess all the other manufacturers also do too. I think anything over 3kW per phase has to have RPC. I just had my 10kW Samil replaced. I can see the settings in the menu but I haven’t got the passwords to dig deeper to see if it responds to frequency as well as voltage. My line voltage here is pretty good so I never see it take effect though.

            Ultimately, if the settings are narrow enough, it should effectively have the effect of increasing inertia to the grid.

            Hope that helps…..

  17. DJR96 4 years ago

    Entirely complements my analysis and report:-

    I assume you’ve all read the reports so far:-

    So after analysing all that I can provide some interesting details.

    Yeah the wind was seriously strong. Seven tornadoes with wind speeds as high as 260kmh developed during the storm, some crossing paths with transmission lines. Little wonder some pylons blew over.

    Yes some of the wind turbines reduced output or disconnected altogether.
    There is a few things going on here.
    Wind turbines need about a 30kmh breeze to generate at full capacity. They can keep generating at full capacity up to around 90kmh at which point they have to reduce to be able to not over-stress the pylon structure it stands on. This likely occurred at some units but it’s not been publicised yet just which ones or by just how much they reduced due to high speed speeds.
    They can tolerate wind gusts over 200kmh, so they’re pretty tough. And in fact none of them suffered any structural damage as a result of the storm.
    Almost all of the wind turbines detected disturbances on the grid (voltage sags/surges) and went into a ‘fault ride-through’ mode. When they do this they also reduce output to keep a buffer up in case of any further irregularities, but soon build back to normal generation if it senses the grid being ok.
    Unfortunately, many of them were also programmed to disconnect altogether if they go into this ride-through mode a number of times. Many only after just two occasions. Others 6 or more.
    So every time there was a fault in the transmission lines, either shorting, disconnecting or even re-closing after a trip, a disturbance occurs that the wind turbines detected.
    Also not made very clear is which wind turbines (if any) had to disconnect because there was no active grid to feed-in to due to failed transmission lines. Just like a home solar inverter, if they’re islanded they can’t operate.
    So yes, a fair chunk of wind capacity was lost due to this. But not due to excessive wind velocity!

    The reports say that the synchronous generation (Torrens Island and Ladbroke Grove), and the Murraylink HVDC transmission line all did what they were supposed to do and weren’t damaged at any time. What it does not say though is whether they were called upon to increase capacity as a result of some of the wind generation dropping off. Because it appears all of the shortfall was being brought in via the Heywood interconnector.

    Now this is the bit the reports don’t cover but if you analyse the graph on page 12 of the first report, you can see the disturbance caused by the 2nd trip of the Davenport-Belalie line at 16:18:09, and the loss of the first group of wind turbines (their 3rd detected fault). Then for 4 seconds after there’s a nice wavy line in the graph. This is due to the synchronous generation in Victoria and Torrens Island nearly losing synchronism. They were starting to fight each other and that puts huge extra loads on the transmission lines connecting them (Heywood). But it recovers after 4-5 seconds. Had that been all the disturbances it would have been all ok despite the Heywood line running more than 100MW over its rated capacity. It was coping.

    But then the Davenport-Mt.Lock line is tripped, and more wind generation is lost, creating another major disturbance which also messed with synchronisation. The system had not recovered from this (needing 4-5 seconds) when an attempt to re-close that line is made, totally screwing up synchronism, this time causing the load through Heywood to spike over 850MW which causes it to trip, disconnecting it from Victoria. Without all that energy coming from Victoria, the remaining generation could not supply demand, voltage and frequency plummeted which tripped all other generation off-line. Black system.

    The ONE thing that could have prevented the black system, was to not attempt re-closing that Davenport-Mt.Lock line. Just when the system urgently needed to be shedding some load, it tried to connect more. The Heywood interconnector was already running over-capacity and the system was struggling to stay synchronised.

    The irony here is that all grid connected inverters, whether that be your home solar system or the big wind turbines, have to by design specified in Australian Standards regulations, check for the presence and quality of the grid before feeding-in any energy.
    I don’t think it is too much to expect that the national grid operators should have to check beforehand whether conditions are safe and capable of connecting transmission lines and other elements before doing so. This would appear to be a monstrous gaping hole in safe operating procedures that need remedial action to ensure a more reliable network. These re-closers need to be centrally controlled and not independent units so that the network monitoring and control computers can manage them.

    AEMO seemed to not be aware of some of the software settings built into the wind turbines. In particular, the ‘number of fault ride-through events before disconnecting’ one.
    The wind turbine operators have all since adjusted them to 20 events.
    Significant generators like these are depended upon and every effort needs to be made to prevent any sudden unexpected losses in generation. It’s fine to ramp up and down at a reasonable rate that allows enough time for other generators to be able to adjust to. If the grid is live, let them generate at any time voltage and frequency is within operating limits. Inverters are capable of operating safely over a much wider voltage and frequency range than synchronous generators. Need to take advantage of that.

    Furthermore, I don’t know whether they already are or not, but they ought to comply with the latest AS4777 standard that requires they have reactive power control. This would see them providing leading phase energy when frequency/voltage on the grid is reduced, and vice-versa. This would provide some active grid support when synchronous generation is struggling. This may be achieved with a software upgrade, or may require a retrofitted control board from the manufacturer. Either way it should not be too difficult to implement, but the benefits very significant. The same also applies to the inverters at each end of the Murraylink HVDC. It too technically could provide the same support.

    So there you have it. Some insights you may not see elsewhere.
    It will be interesting to see if AEMO recognises these issues too.
    We’ll await their final report later this month.

    • permaculture utopia 4 years ago

      What’s laughable is so called “synchronous generators” which are already supplying power struggling to stay synchronised with each other, when offline inverter controlled storage will sync in milliseconds.

      • DJR96 4 years ago

        Exactly right. I saw it in that one graph in the preliminary report from AEMO. The major issue was staring at them all this time and they’ve only (reluctantly) recognising it now.
        The NEM is so 20th century. It has to transition into the 21st century. It’s going to take some very big fundamental shifts in the way they operate.

        And this proposed 100MW battery storage facility will be able to demonstrate all the advantages of building a NEM around inverters instead of synchronous generators.

        • permaculture utopia 4 years ago

          The other thing the event appears to illustrate is the wind turbines have the ability to quickly resynchronise in frequency and voltage disturbances with their ride through capability. Seems this ride through capability has proven reliable up to the point the ride through functionality was programmed to terminate due to repeated network disruptions.

          • DJR96 4 years ago

            That 4 to 5 seconds is the time the governors regulating the rotational speed (and hence frequency Hz) took to correct the synchronisation between itself and the power coming via the interconnecter from Victoria. That’s with everything actually running close to speed, just a final correction.
            Starting from cold, even gas turbines need 10-15 minutes before they’re ready to feed-in energy, and that’s quick. Anything steam powered takes hours.

            A running inverter, whether that be your roof-top solar or the wind turbines AND the receiving end of the Murraylink HVDC, are all followers. They follow what ever the frequency of the grid is that it is connected to. Instantaneously and accurately.
            But note that they can only operate if there is an operational grid there to start with. They sense the presence of and synchronise to the grid. And AS4777 requires that they sense this for between 60 and 90 seconds before they start feeding in energy. So by the standard they have to take that long when starting up. Technically they could actually start in under a second.
            But it is a necessary requirement. If a line goes down, the grid will usually automatically try to re-connect the line. If the fault is still there it will trip a second time and then stay locked out. You don’t really want inverters trying to start up when the grid is trying to sort itself out.

          • permaculture utopia 4 years ago

            “You don’t really want inverters trying to start up when the grid is trying to sort itself out.”

            Throwing out all previous assumptions, it seems logical the most accurate and reliable generators need to set the clock speed. In my mind, a battery fed inverter has the most precise 50Hz waveform.

          • DJR96 4 years ago

            You’re so on to it!
            The grid needs a master inverter at it’s core that runs the 50Hz. Everything else, including the synchronous generation, needs to follow that master inverter.

            That’s why this 100MW battery storage plant proposed for SA could be a real test case.
            Under certain circumstances – when there is plenty of wind and solar power – it would be possible to disconnect from Victoria. The inverter at the battery become the master setting the frequency. All the wind, solar and the Murraylink continue to follow as they do now. And I believe you could still have the local gas generation contributing. They would have to follow the frequency which means they would have to use voltage regulation to react much quicker. Their output would be relatively variable, but the inverter and battery storage can smooth that out completely. And you can do this with a battery that is as little as 5% of the grid capacity.

          • permaculture utopia 4 years ago

            I know at a small scale, all the inverter/chargers are the same and can be programmed as a master or a slave with DIP switches, or loading the device with new settings through a cord to a computer, or remotely via the internet. Perhaps reprogramming utility level inverters or fossil fuel generators is no big deal either.

          • DJR96 4 years ago

            The master/slave thing that some inverters currently can do is usually for the purpose of getting three single phase units to operate as one three phase unit. One is set as the master and it follows the grid. The other two are slaves that then operate at 120 degrees from the master.

            But as you can imagine, it would not be that difficult to reprogram an inverter to achieve other modes of operation.

            Check this out:- (6.1Mb)

          • permaculture utopia 4 years ago

            With this link, are you suggesting this equipment can be used to replace the current grid/s? Could it be configured for City Councils or regional areas, so they can stand alone when long runs of poles and wires are damaged and reconnect to the larger state grid when it is repaired?

          • Nick 4 years ago

            That’s impossible without an infinitely large battery. What you’re describing is an isochronous generator (or I suppose an isochronous battery). An isoch unit is a constant frequency unit. But to hold constant frequency, it needs to be able to change its power up and down to keep the power flowing into the system equal to the power flowing out. Without that balance, the frequency will deviate off the nominal 50 Hz.

          • permaculture utopia 4 years ago

            My inverter/charger can produce a constant 50Hz, or be programmed to connect to and sync with an external AC source, locally it can be programmed to function as a master or among other slaves. The system can be programmed to supply the load from batteries or to keep the batteries charged. It has five profiles for grid interaction. It is a computer controlled energy management system. I’m sure bigger utility level models have the same flexibility.

          • Nick 4 years ago

            Your inverter can produce a constant 50 Hz, or it can be tied to the external AC source. It cannot do both. Neither can larger utility models. It’s one or the other.

          • permaculture utopia 4 years ago

            Actually, my inverter/charger can power a local load and if it finds its peak power output is insufficient, it can connect and sync to a remote AC source during those milliseconds. Inverter/chargers such as this could power a City Council or regional area, and only sync with a larger grid to top up peak output power or charge batteries in winter, or automatically disconnect from the larger grid if its long runs of poles and wires fall over. So yes, in a way, the inverter/charger can produce a constant 50Hz and at other times when needed, automatically be a follower. It’s a truly flexible device of the future and will supersede all other inferior technology.

          • DJR96 4 years ago

            Sorry, but Nick is actually right here.
            Your true hybrid inverter as you say has several modes of operation and you can set an order of preference of those modes.
            One being stand-alone and has no interaction with the grid.
            The mode you probably have it set at is grid interactive. It will use local generation (solar I’m guessing) to run loads, if there is more available it will charge your battery pack, if that is fully charged or there is more than both the loads and charger can use it will then export to grid.
            At any time it is connected to the grid (not necessarily using power from the grid) it will be synchronised to the grid and be following it. If at any time the grid fails, the inverter is able to immediately continue running at it’s own 50Hz using energy from the battery. When the grid is restored, it will have to go through the same process as other inverters as per AS4777, sense the grid and wait 60-90 seconds before feeding-in any energy. During that time it will adjust its own frequency to re-synchronise with the grid.

          • permaculture utopia 4 years ago

            It really does have the third midway option. In the context of developing countries this has the advantage of loads working on a constant onsite 50Hz much of the time when the device is able to supply all the power needed by the loads, however it can quickly sync to a weak external AC source, to accept a wide frequency variation or low voltage, for those milliseconds it needs to connect. This mostly protects the local gear from undue deterioration from weak grids. This is what this feature is for. So the clock might look like this 50Hz 50Hz 50Hz then need more peak power momentarily so connect to weak grid 48Hz 47Hz disconnect from weak grid 50Hz 50Hz 50Hz…

          • permaculture utopia 4 years ago

            Here’s the profiles for grid interaction currently loaded into my inverter/charger. Can see option 3 is “Disconnect from the mains when possible”. This enables the device to only connect to the grid to export excess solar power and to quickly connect to the grid to back up its peak power. This feature is for locations where the grid is often weak and unreliable, though is still utilised the extent it can be. This company was established in 1975 and has built systems for community infrastructure in developing countries like hospitals, lighthouses, resorts etc

  18. DJR96 4 years ago


    Having analysed the third report from AEMO ( ), which has significantly more information and observations, I have concluded these points:-

    • As a result of the sixth disturbance, when the Davenport-Mt.Lock transmission line tripped, a group of wind turbines reduced their output.
    • This significant drop in generation not only caused a drop in voltage, but started a divergence in frequency between SA and Vic. This can be seen in Figure 12, p.43.
    • The Torrens Island generators indicated a brief increase in output that is attributable to inertia response. That response comes at the cost of frequency reduction. Inertia can not provide extra power without losing frequency. It is a problematic characteristic too relied upon.
    • Torrens Island was not participating in FCAS with the NEM so it was not even required to have a governor response to attempt correcting frequency. Meaning it would not have contributed much, if anything, to increasing the frequency back towards 50Hz. (Unless load was shed.)
    • At this point the frequency diverged between Victoria and SA.
    • The frequency at South East followed most closely with Heywood in Victoria, not SA.
    • The Ladbroke Grove generators being located close to South East followed the frequency of the inter-connector. Meaning their inertia was not contributing much towards maintaining frequency in the rest of SA.
    • This diverging frequency is indicated in Figure 13, p44 as phase angle difference. This is exactly as I described beforehand.
    • Note too that the phase angle had not fully re-aligned after the previous (5th)disturbance at 16:18:08. Previously I had said it needed 4-5 seconds for this to occur. But without governor response from Torrens Island this was going to take much longer to correct itself.
    • Most of the wind turbines that were still contributing power at the time were injecting some of their energy as reactive power which would provide some level of network assistance. But I suspect the settings for this are too wide to provide the sensitivity required to be effective soon enough. ie. The network has to be quite bad before it’ll start helping.
    • When the phase angle difference became too great, the synchronism relay at South East tripped the circuit breaker disconnecting the inter-connector from Heywood. Note that the actual trip and disconnection was due to the protection of the synchronism relay, not because of over-current.
    • Quote from p45:- “It was the combination of high currents and low voltages that resulted in activation of Heywood loss of synchronism relay rather than the sheer size of current (over-load).” AEMO doesn’t seem to comprehend the severe effect diverging phase angle has. That they start fighting against each other causing the low voltage/high currents. The low voltage/high current state is only occurring due to loss of synchronism.
    • This separation/disconnection has occurred a number of times in the past. Always as a result of loss of synchronism, not just over-current. In prior events there have been at least 2.5 times more synchronous generation at the time, providing the inertia to make the phase divergence time longer, allowing the UFLS time to take effect, and allow SA to run as an island after the inter-connector trips.
    • Once separated from the rest of the NEM, Torrens Island was the only means of running SA in island mode, it was the only remaining facility capable of providing a frequency reference. But it was both ungoverned and its frequency (phase angle) was diverged from Ladbroke Groves generators. Meaning it was impossible for it to continue. It never stood a chance. SA could never run in island mode that day!
    • AEMO not requiring Torrens Island to perform FCAS when it was the only operating facility capable of providing it is simply unfathomable. What were they thinking!?
    • Note that all the operating wind turbines and the Murraylink are “followers” to the network. Without an operational network they can do nothing and must disconnect.
    • Many of the elements that make up this event have occurred before. AEMO had prior experience. But it would seem they did not do anything to mitigate another event despite this experience.

    As many would have you believe, there needs to be considerably more local synchronous generation to provide better stability and reliability. Which IS true for the current way the NEM is operated.

    But we know the NEM IS in a transition towards more renewable generation, and the SA situation is simply the leading edge to it. A technological solution will need to be implemented to reduce or eliminate the dependence of synchronous generation and the “inertia” that it provides. To make any significant improvements to the network in the future this is essential.
    I am confident such a solution already exists, but AEMO’s mindset seems stuck in 20th century tech and unwilling to consider alternatives. It is unwilling to even allow the existing renewable technology to provide support to the grid despite the tech being able to do so much more than it currently is. A grossly under-utilized opportunity simply because they don’t fully comprehend its abilities.

    I believe this black system event and with Hazelwood closing next year, they’ll be forced into thinking more laterally. One of their current reports calls for more transmission lines between Victoria and SA, at something like a $1.4billion cost. This seems pointless if there is going to be less energy generated in Victoria to transfer. The money would clearly be better invested in another solution.

    Do I have that solution? Well, I am working on something. A work in progress that will need modelling and verification, but I believe it should work. But that is for another time to elaborate.

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