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tech / sci.electronics.design / Grid Stability and Renewable Power

SubjectAuthor
* Grid Stability and Renewable PowerRicky
+- Re: Grid Stability and Renewable PowerKlaus Kragelund
+* Re: Grid Stability and Renewable PowerPhil Allison
|`- Re: Grid Stability and Renewable PowerRicky
+* Re: Grid Stability and Renewable Powerwhit3rd
|`- Re: Grid Stability and Renewable PowerJan Panteltje
+* Re: Grid Stability and Renewable PowerMartin Brown
|`* Re: Grid Stability and Renewable PowerRicky
| `* Re: Grid Stability and Renewable PowerMartin Brown
|  `- Re: Grid Stability and Renewable PowerRicky
+- Re: Grid Stability and Renewable PowerGlen Walpert
`* Re: Grid Stability and Renewable PowerPhil Allison
 +* Re: Grid Stability and Renewable PowerRicky
 |`* Re: Grid Stability and Renewable PowerPhil Allison
 | `- Re: Grid Stability and Renewable PowerRicky
 `* Re: Grid Stability and Renewable PowerJeff Liebermann
  +- Re: Grid Stability and Renewable PowerPhil Allison
  +* Re: Grid Stability and Renewable PowerRicky
  |`- Re: Grid Stability and Renewable PowerJeff Liebermann
  +* Re: Grid Stability and Renewable PowerBertrand Sindri
  |`- Re: Grid Stability and Renewable PowerJeff Liebermann
  `* Re: Grid Stability and Renewable PowerPhil Allison
   `* Re: Grid Stability and Renewable PowerRicky
    `* Re: Grid Stability and Renewable PowerMartin Brown
     +* Re: Grid Stability and Renewable PowerPhil Allison
     |`* Re: Grid Stability and Renewable Powerwhit3rd
     | +- Re: Grid Stability and Renewable PowerJeroen Belleman
     | +- Re: Grid Stability and Renewable PowerRicky
     | `* Re: Grid Stability and Renewable PowerGlen Walpert
     |  `- Re: Grid Stability and Renewable PowerRicky
     `- Re: Grid Stability and Renewable PowerDon Y

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Grid Stability and Renewable Power

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Subject: Grid Stability and Renewable Power
From: gnuarm.d...@gmail.com (Ricky)
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 by: Ricky - Mon, 18 Apr 2022 03:01 UTC

Is there some fundamental reason why renewable power sources on the grid can't provide the equivalent of "inertia", to stabilize the grid?

It seems to me the only issue is normally renewable power sources are optimized to provide the maximum power possible, so if the grid frequency slows (because there is less power sourced than the power drained), renewable power generation is already maxed out.

So would operating at a few percent below optimum provide adequate energy margin to act to stabilize the grid? If the frequency drops, the renewable power sources pull in efficiency a bit to pump more energy into the grid and bring back up the frequency. If the grid frequency drops, the renewable power sources drop back on the efficiency a small bit and the lower output again stabilizes the grid.

Is this not adequate in some way? Is operating a couple of percent off optimum not acceptable? Does anyone actually know the answer rather than speculating?

Of course, this won't eliminate the need for grid storage for intermittent power sources. But it would solve the problem of short term grid stability with renewable energy sources.

Someone is trying to tell me that using inverters makes it impossible to use them for grid stability, which makes no sense to me. Then again, I believe people here have shown that wind turbines don't use inverters. AC is generated directly in the generator without inverters.

--

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209

Re: Grid Stability and Renewable Power

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From: klausk...@hotmail.com (Klaus Kragelund)
Newsgroups: sci.electronics.design
Subject: Re: Grid Stability and Renewable Power
Date: Mon, 18 Apr 2022 09:34:18 +0300
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 by: Klaus Kragelund - Mon, 18 Apr 2022 06:34 UTC

18.04.22 06:01, Ricky wrote:
>Is there some fundamental reason why renewable power sources on the grid can't provide the equivalent of "inertia", to stabilize the grid?
>
>It seems to me the only issue is normally renewable power sources are optimized to provide the maximum power possible, so if the grid frequency slows (because there is less power sourced than the power drained), renewable power generation is already maxed out.
>
>So would operating at a few percent below optimum provide adequate energy margin to act to stabilize the grid? If the frequency drops, the renewable power sources pull in efficiency a bit to pump more energy into the grid and bring back up the frequency. If the grid frequency drops, the renewable power sources drop back on the efficiency a small bit and the lower output again stabilizes the grid.
>
>Is this not adequate in some way? Is operating a couple of percent off optimum not acceptable? Does anyone actually know the answer rather than speculating?
>
>Of course, this won't eliminate the need for grid storage for intermittent power sources. But it would solve the problem of short term grid stability with renewable energy sources.
>
>Someone is trying to tell me that using inverters makes it impossible to use them for grid stability, which makes no sense to me. Then again, I believe people here have shown that wind turbines don't use inverters. AC is generated directly in the generator without inverters.
>

Older systems with high percentage of old style synchronized high inertia generators provided good stability

In the future more generated power will be decentralized, so you need a distributed communication channel to set the duty point of the majority of the power generated

AFAIK most solar systems are current sources with no knowledge of grid state, resulting in VAR squishing around on the grid

--
Klaus

Re: Grid Stability and Renewable Power

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Subject: Re: Grid Stability and Renewable Power
From: palliso...@gmail.com (Phil Allison)
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 by: Phil Allison - Mon, 18 Apr 2022 07:17 UTC

Ricky wrote:
==========
>
> Is there some fundamental reason why renewable power sources on the grid can't provide the equivalent of "inertia", to stabilize the grid?
>

** They do that right now and for the past 100 years.

Hydro power stations are the main frequency regulating elements in a grid.
Certainly here on the east cost of Australia ( Snowy River Scheme) and I bet in any other place blessed with hydro.

Reasons being that generation can be fine controlled almost instantly in response to frequency deviations and permanently availability when a number of dams and stations are involved.

The permanently part arises form the ability pump water up hill and keep a few dams full at all times.
Sun light and wind are God's domain, not human controlled.

....... Phil

Re: Grid Stability and Renewable Power

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Subject: Re: Grid Stability and Renewable Power
From: whit...@gmail.com (whit3rd)
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 by: whit3rd - Mon, 18 Apr 2022 07:51 UTC

On Sunday, April 17, 2022 at 8:01:27 PM UTC-7, Ricky wrote:
> Is there some fundamental reason why renewable power sources on the grid can't provide the equivalent of "inertia", to stabilize the grid?

What is the 'inertia' analogy, exactly? Most renewable power sources aren't like hydroelectric, with large
stored reserves and quick access to extra generating capacity, but a 'grid' can have (and use) a variety of
sources, including some with stored reserves, in cooperative fashion.

It's a stable grid if its management has the right combination of feedback and time delays... just like
a compensated op amp.

[about solar photovoltaics]
> Someone is trying to tell me that using inverters makes it impossible to use them for grid stability, which makes no sense to me.

If by that they mean inverters that aren't managed as part of the overall grid, but which are always-full-power,
then the feedback requirement isn't met. So it does make some sense. The photovoltaic output would have
to exceed the sum of easily-controlled other sources, or have abrupt transitions that exceed slew rate
of the grid-control options. Or, the grid control would have to be badly designed.

Re: Grid Stability and Renewable Power

<t3j9d8$u5r$2@dont-email.me>

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From: pNaonStp...@yahoo.com (Jan Panteltje)
Newsgroups: sci.electronics.design
Subject: Re: Grid Stability and Renewable Power
Date: Mon, 18 Apr 2022 08:59:31 GMT
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 by: Jan Panteltje - Mon, 18 Apr 2022 08:59 UTC

On a sunny day (Mon, 18 Apr 2022 00:51:00 -0700 (PDT)) it happened whit3rd
<whit3rd@gmail.com> wrote in
<eabbe49a-d070-4224-b10f-629921a15f5fn@googlegroups.com>:

>On Sunday, April 17, 2022 at 8:01:27 PM UTC-7, Ricky wrote:
>> Is there some fundamental reason why renewable power sources on the grid can't provide the equivalent of "inertia", to
>> stabilize the grid?
>
>What is the 'inertia' analogy, exactly? Most renewable power sources aren't like hydroelectric, with large
>stored reserves and quick access to extra generating capacity, but a 'grid' can have (and use) a variety of
>sources, including some with stored reserves, in cooperative fashion.
>
>It's a stable grid if its management has the right combination of feedback and time delays... just like
>a compensated op amp.
>
>[about solar photovoltaics]
>> Someone is trying to tell me that using inverters makes it impossible to use them for grid stability, which makes no sense to
>> me.
>
>If by that they mean inverters that aren't managed as part of the overall grid, but which are always-full-power,
>then the feedback requirement isn't met. So it does make some sense. The photovoltaic output would have
>to exceed the sum of easily-controlled other sources, or have abrupt transitions that exceed slew rate
>of the grid-control options. Or, the grid control would have to be badly designed.

Molten salt sun power plants use 'inertia' to supply power day and night:
https://www.yara.com/chemical-and-environmental-solutions/solar-power-molten-salt/

Re: Grid Stability and Renewable Power

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From: '''newsp...@nonad.co.uk (Martin Brown)
Newsgroups: sci.electronics.design
Subject: Re: Grid Stability and Renewable Power
Date: Mon, 18 Apr 2022 10:45:24 +0100
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 by: Martin Brown - Mon, 18 Apr 2022 09:45 UTC

On 18/04/2022 04:01, Ricky wrote:
> Is there some fundamental reason why renewable power sources on the
> grid can't provide the equivalent of "inertia", to stabilize the
> grid?

Part of the problem in the UK was that because of micro generation on
individual home roofs have to self protect their 4kW rated kit if the
load gets too far off specification they each make an independent
decision to disconnect leading to a runaway cascade failure.

That is part of what the technical investigation into the big UK
powercut that took down most of London and the SE in August 2019.

The other snag was that the low frequency demand disconnect system
dropped both load and active generation capacity on home roofs so that
the numbers no longer added up. Net load shed was much less than the
absolute load shed (because of local PV generation on roofs).

https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/836626/20191003_E3C_Interim_Report_into_GB_Power_Disruption.pdf

It is a case study in how adding renewables to the mix effectively
destabilised the network because some of the new protections on big
offshore windfarms were untested/incorrect and conceptually flawed.
>
> It seems to me the only issue is normally renewable power sources are
> optimized to provide the maximum power possible, so if the grid
> frequency slows (because there is less power sourced than the power
> drained), renewable power generation is already maxed out.

The grid is generally balanced by dumping all residual power into
electrolytic aluminium or brine plants that can absorb any amount of
energy and can change how much they take in an instant. They do require
a certain amount of power to stay hot/warm but can vary their
consumption by two or possibly three orders of magnitude when required.
>
> So would operating at a few percent below optimum provide adequate
> energy margin to act to stabilize the grid? If the frequency drops,
> the renewable power sources pull in efficiency a bit to pump more
> energy into the grid and bring back up the frequency. If the grid
> frequency drops, the renewable power sources drop back on the
> efficiency a small bit and the lower output again stabilizes the
> grid.

No. The individual domestic systems will each try to save themselves
when the network conditions become adverse. Only really big generators
can provide the inertia (pumped storage or solid state huge batteries)

Neither can provide a long term solution so if some more conventional
power doesn't come back onstream before it runs out you are stuck.

The ultimate sanction is that the grid will shed great chunks of load
until it is able to get the frequency back under control. The
calculation of how much has been greatly complicated by solar PV.

> Is this not adequate in some way? Is operating a couple of percent
> off optimum not acceptable? Does anyone actually know the answer
> rather than speculating?

There is no point in operating at anything other than peak efficiency.
The grid is always balanced for consumption and generation with the
loads of last resort taking up any instantaneous slack. They also get
dumped off first if there is a glitch.

> Of course, this won't eliminate the need for grid storage for
> intermittent power sources. But it would solve the problem of short
> term grid stability with renewable energy sources.

How? Each of the toy systems on a home will make its own decision about
when to drop off as the frequency goes out of spec. You probably could
allow them some more leeway to stay on grid for longer.

Nothing can really get around the fact that if the house they are on
gets disconnected from the grid by load shedding their contribution
(which during daytime might well be net positive) is lost.

The calculation that wasn't allowed for in the UK is that with domestic
generation on home roofs and on a sunny day when you shed "load" you
will also shed a whole bunch of local solar PV generation as well.

--
Regards,
Martin Brown

Re: Grid Stability and Renewable Power

<k2d7K.361496$Gojc.226527@fx99.iad>

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From: nos...@null.void (Glen Walpert)
Subject: Re: Grid Stability and Renewable Power
Newsgroups: sci.electronics.design
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 by: Glen Walpert - Mon, 18 Apr 2022 12:44 UTC

On Sun, 17 Apr 2022 20:01:23 -0700 (PDT), Ricky wrote:

> Is there some fundamental reason why renewable power sources on the grid
> can't provide the equivalent of "inertia", to stabilize the grid?
>
> It seems to me the only issue is normally renewable power sources are
> optimized to provide the maximum power possible, so if the grid
> frequency slows (because there is less power sourced than the power
> drained), renewable power generation is already maxed out.
>
> So would operating at a few percent below optimum provide adequate
> energy margin to act to stabilize the grid? If the frequency drops, the
> renewable power sources pull in efficiency a bit to pump more energy
> into the grid and bring back up the frequency. If the grid frequency
> drops, the renewable power sources drop back on the efficiency a small
> bit and the lower output again stabilizes the grid.
>
> Is this not adequate in some way? Is operating a couple of percent off
> optimum not acceptable? Does anyone actually know the answer rather
> than speculating?
>
> Of course, this won't eliminate the need for grid storage for
> intermittent power sources. But it would solve the problem of short
> term grid stability with renewable energy sources.
>
> Someone is trying to tell me that using inverters makes it impossible to
> use them for grid stability, which makes no sense to me. Then again, I
> believe people here have shown that wind turbines don't use inverters.
> AC is generated directly in the generator without inverters.

This is an active area of R&D, and there have been some pretty
significant developments which seem to have gone by unnoticed by most,
namely code changes mandating the use of inverters compliant with UL1741
SA. This changed the requirements for grid connected inverters from a
very simple "disconnect immediately when the grid goes out of a very
narrow definition of normal and reconnect after the grid has been normal
for 5 minutes" requirement ("Grid Interactive"), to a much more
sophisticated "Grid Support" requirement, where inverters are required to
help stabilize the grid. They can do this more effectively than large
rotating generators because their response time is /much/ faster.

UL1741 SA (Supplement A) has since been rolled into Rev 1 of the base
UL1741 spec, but SA is still a good search term. The only accurate
description of these requirements I have found, short of shelling out
thousands on specs, is a one hour seminar available on the UL web site,
registration required. There is a lot of BS on all other sources I have
seen, mostly people don't seem to understand the relationship between
reactive power and grid voltage (Grid Support inverters supply reactive
power to the grid to help correct under voltage even if they are already
at maximum output; they can deliver significant reactive power with only
a small reduction in real power, and reactive power is more effective in
boosting grid voltage than real power due to the characteristics of the
rotating generators and motors on the grid. (By convention capacitors
supply reactive power and inductive loads use it.)

Requirements for grid connection of any power source are published in a
utilities SRD (Source Requirements Document), and as far as I know all US
utilities SRDs have required Grid Support inverters since 2020, and they
are also required by the current NEC.

Some utilities, Hawaii and possibly others, also reserve the right to
require a SCADA-like monitoring and control network connection to your
inverter - they want your knobs :-).

There have been similar code changes in Canada and the EU.

IEEE refers to grid connected inverters as "static synchronous
generators" and the old-fashioned type as "rotary synchronous generators"
in newer specs, liberally referenced by UL.

Glen

Re: Grid Stability and Renewable Power

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Subject: Re: Grid Stability and Renewable Power
From: gnuarm.d...@gmail.com (Ricky)
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 by: Ricky - Mon, 18 Apr 2022 14:34 UTC

On Monday, April 18, 2022 at 3:17:17 AM UTC-4, palli...@gmail.com wrote:
> Ricky wrote:
> ==========
> >
> > Is there some fundamental reason why renewable power sources on the grid can't provide the equivalent of "inertia", to stabilize the grid?
> >
> ** They do that right now and for the past 100 years.
>
> Hydro power stations are the main frequency regulating elements in a grid.
> Certainly here on the east cost of Australia ( Snowy River Scheme) and I bet in any other place blessed with hydro.
>
> Reasons being that generation can be fine controlled almost instantly in response to frequency deviations and permanently availability when a number of dams and stations are involved.
>
> The permanently part arises form the ability pump water up hill and keep a few dams full at all times.
> Sun light and wind are God's domain, not human controlled.

OTHER than hydro... of course.

--

Rick C.

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Subject: Re: Grid Stability and Renewable Power
From: gnuarm.d...@gmail.com (Ricky)
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 by: Ricky - Mon, 18 Apr 2022 14:43 UTC

On Monday, April 18, 2022 at 5:45:31 AM UTC-4, Martin Brown wrote:
> On 18/04/2022 04:01, Ricky wrote:
> > Is there some fundamental reason why renewable power sources on the
> > grid can't provide the equivalent of "inertia", to stabilize the
> > grid?
> Part of the problem in the UK was that because of micro generation on
> individual home roofs have to self protect their 4kW rated kit if the
> load gets too far off specification they each make an independent
> decision to disconnect leading to a runaway cascade failure.
>
> That is part of what the technical investigation into the big UK
> powercut that took down most of London and the SE in August 2019.
>
> The other snag was that the low frequency demand disconnect system
> dropped both load and active generation capacity on home roofs so that
> the numbers no longer added up. Net load shed was much less than the
> absolute load shed (because of local PV generation on roofs).
>
> https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/836626/20191003_E3C_Interim_Report_into_GB_Power_Disruption.pdf
>
> It is a case study in how adding renewables to the mix effectively
> destabilised the network because some of the new protections on big
> offshore windfarms were untested/incorrect and conceptually flawed.
> >
> > It seems to me the only issue is normally renewable power sources are
> > optimized to provide the maximum power possible, so if the grid
> > frequency slows (because there is less power sourced than the power
> > drained), renewable power generation is already maxed out.
> The grid is generally balanced by dumping all residual power into
> electrolytic aluminium or brine plants that can absorb any amount of
> energy and can change how much they take in an instant. They do require
> a certain amount of power to stay hot/warm but can vary their
> consumption by two or possibly three orders of magnitude when required.
> >
> > So would operating at a few percent below optimum provide adequate
> > energy margin to act to stabilize the grid? If the frequency drops,
> > the renewable power sources pull in efficiency a bit to pump more
> > energy into the grid and bring back up the frequency. If the grid
> > frequency drops, the renewable power sources drop back on the
> > efficiency a small bit and the lower output again stabilizes the
> > grid.
> No. The individual domestic systems will each try to save themselves
> when the network conditions become adverse. Only really big generators
> can provide the inertia (pumped storage or solid state huge batteries)
>
> Neither can provide a long term solution so if some more conventional
> power doesn't come back onstream before it runs out you are stuck.
>
> The ultimate sanction is that the grid will shed great chunks of load
> until it is able to get the frequency back under control. The
> calculation of how much has been greatly complicated by solar PV.
> > Is this not adequate in some way? Is operating a couple of percent
> > off optimum not acceptable? Does anyone actually know the answer
> > rather than speculating?
> There is no point in operating at anything other than peak efficiency.
> The grid is always balanced for consumption and generation with the
> loads of last resort taking up any instantaneous slack. They also get
> dumped off first if there is a glitch.
> > Of course, this won't eliminate the need for grid storage for
> > intermittent power sources. But it would solve the problem of short
> > term grid stability with renewable energy sources.
> How? Each of the toy systems on a home will make its own decision about
> when to drop off as the frequency goes out of spec. You probably could
> allow them some more leeway to stay on grid for longer.
>
> Nothing can really get around the fact that if the house they are on
> gets disconnected from the grid by load shedding their contribution
> (which during daytime might well be net positive) is lost.
>
> The calculation that wasn't allowed for in the UK is that with domestic
> generation on home roofs and on a sunny day when you shed "load" you
> will also shed a whole bunch of local solar PV generation as well.

Let's leave the small, domestic systems out of the conversation. The particular point someone was making was that no inverters used with wind power (or solar farms) has the ability to help stabilize the grid, because there is no rotating inertia. It was not claimed that this was not possible, but it was implied by pointing out no one had done this yet and it would be a very useful feature.

Seems to me it would require some way of increasing the power output, which means the facility has to run below optimal efficiency to have anything in reserve.

The advantage of natural inertia, is the continuous nature. As much energy as is needed is available if you are able to tolerate the reduction in frequency. Of course, there is a limit to the inertia available, but it seems to do the job pretty well in most cases, while currently we seem to get nothing from solar and wind power facilities.

--

Rick C.

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Subject: Re: Grid Stability and Renewable Power
From: palliso...@gmail.com (Phil Allison)
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 by: Phil Allison - Mon, 18 Apr 2022 21:51 UTC

Ricky wrote:
===========
>
> Is there some fundamental reason why renewable power sources on the grid can't
> provide the equivalent of "inertia", to stabilize the grid?
>
> It seems to me the only issue is normally renewable power sources are optimized to
> provide the maximum power possible, so if the grid frequency slows (because there
> is less power sourced than the power drained), renewable power generation is already maxed out.

** What happens now is that inverters feeding the grid *track* the existing frequency - cos they are minor players in supplying the load.
But what if that were not the case, they became the majority suppliers and and instead were locked to a central clock ?

Rotating machines would then follow them.

....... Phil

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Subject: Re: Grid Stability and Renewable Power
From: gnuarm.d...@gmail.com (Ricky)
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 by: Ricky - Mon, 18 Apr 2022 22:37 UTC

On Monday, April 18, 2022 at 5:51:42 PM UTC-4, palli...@gmail.com wrote:
> Ricky wrote:
> ===========
> >
> > Is there some fundamental reason why renewable power sources on the grid can't
> > provide the equivalent of "inertia", to stabilize the grid?
> >
> > It seems to me the only issue is normally renewable power sources are optimized to
> > provide the maximum power possible, so if the grid frequency slows (because there
> > is less power sourced than the power drained), renewable power generation is already maxed out.
> ** What happens now is that inverters feeding the grid *track* the existing frequency - cos they are minor players in supplying the load.
> But what if that were not the case, they became the majority suppliers and and instead were locked to a central clock ?
>
> Rotating machines would then follow them.

That's a weird thing to say. If the "inverters" were locked to a central clock and driving the grid, rotating generators would be no different than they are now, following the grid.

The grid is very complex. Many different actors, who is leading and who is following in this dance? It's not quite so simple. That's why rotational inertia is useful.

--

Rick C.

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Subject: Re: Grid Stability and Renewable Power
From: palliso...@gmail.com (Phil Allison)
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 by: Phil Allison - Tue, 19 Apr 2022 00:07 UTC


Ricky the IDIOT wrote:
==================
> >>
> > > Is there some fundamental reason why renewable power sources on the grid can't
> > > provide the equivalent of "inertia", to stabilize the grid?
> > >
> > > It seems to me the only issue is normally renewable power sources are optimized to
> > > provide the maximum power possible, so if the grid frequency slows (because there
> > > is less power sourced than the power drained), renewable power generation is already maxed out.
> > ** What happens now is that inverters feeding the grid *track* the existing frequency - cos they are minor players in supplying the load.
> > But what if that were not the case, they became the majority suppliers and and instead were locked to a central clock ?
> >
> > Rotating machines would then follow them.
>
> That's a weird thing to say. If the "inverters" were locked to a central clock and driving the grid,
> rotating generators would be no different than they are now, following the grid.

** Whaaaaaaatttttt ??????

Insane, retarded crap.

....... Phil

Re: Grid Stability and Renewable Power

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Subject: Re: Grid Stability and Renewable Power
Date: Mon, 18 Apr 2022 17:28:06 -0700
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 by: Jeff Liebermann - Tue, 19 Apr 2022 00:28 UTC

On Mon, 18 Apr 2022 14:51:38 -0700 (PDT), Phil Allison
<pallison49@gmail.com> wrote:

>Ricky wrote:
>===========
>>
>> Is there some fundamental reason why renewable power sources on the grid can't
>> provide the equivalent of "inertia", to stabilize the grid?
>>
>> It seems to me the only issue is normally renewable power sources are optimized to
>> provide the maximum power possible, so if the grid frequency slows (because there
>> is less power sourced than the power drained), renewable power generation is already maxed out.
>
>** What happens now is that inverters feeding the grid *track* the existing frequency - cos they are minor players in supplying the load.
> But what if that were not the case, they became the majority suppliers and and instead were locked to a central clock ?
>
> Rotating machines would then follow them.
>
>...... Phil

Synchronizing grid tied inverters and generators using GPS clocks and
GPS disciplined oscillators is a common topic for green research
papers. For example:
"How Microsynchrophasors Could Keep Solar-Saturated Grids Stable"
<https://www.greentechmedia.com/articles/read/How-Microsynchrophasors-Could-Keep-Solar-Saturated-Grids-Stable>

The fun begins if the grid frequency slows down a little due to a
decrease in source supply or an increase in load. A short while
later, the generators are adjusted to bring everything back to exactly
50 or 60Hz. However, that's not good because the frequency also needs
to be adjusted to compensate for the time lost during the power sag.
Otherwise, all the power line driven synchronous motor clocks would
runs slow. So, the frequency of the entire grid needs to be increased
slightly until the lost milliseconds are recovered, when it is now
safe to return to exactly 50 or 60Hz. This explains the basics of how
it's done:
<https://www.mainsfrequency.com/gridtime.php>
Notice that the example shows that Swiss time was 160 seconds behind
UTC in June 2013. At 50Hz, that's
160sec * 50cycles/sec = 8,000
clock cycles that need to added to the grid for grid time to catch up
with UTC time. Looking at the graph (blue line), time still hasn't
caught up 6 months later.

Bottom line is that synchronizing grid tied inverters is certainly
possible, but isn't quite as simple as it might initially appear.

Trivia For UK grid:
<http://www.gridwatch.templar.co.uk>
<https://jeelabs.org/2016/06/keeping-track-of-time/>
<https://www.dynamicdemand.co.uk/grid.htm>
<https://www.mainsfrequency.com>

--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

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Date: Mon, 18 Apr 2022 18:13:17 -0700 (PDT)
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Subject: Re: Grid Stability and Renewable Power
From: palliso...@gmail.com (Phil Allison)
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 by: Phil Allison - Tue, 19 Apr 2022 01:13 UTC

jeff.li...@gmail.com wrote:
======================
Phil Allison
>> >
> >** What happens now is that inverters feeding the grid *track* the existing frequency - cos they are minor players in supplying the load.
> > But what if that were not the case, they became the majority suppliers and and instead were locked to a central clock ?
> >
> > Rotating machines would then follow them.
> >
> Synchronizing grid tied inverters and generators using GPS clocks and
> GPS disciplined oscillators is a common topic for green research
> papers.

** Nice to know, I was just speculating.

> The fun begins if the grid frequency slows down a little due to a
> decrease in source supply or an increase in load.

** Errrr - why ??

Alternators naturally slow in reaction to load, but not inverters.
Plus all alternators in a grid are locked together in phase.

....... Phil

Re: Grid Stability and Renewable Power

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Subject: Re: Grid Stability and Renewable Power
From: gnuarm.d...@gmail.com (Ricky)
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 by: Ricky - Tue, 19 Apr 2022 01:52 UTC

On Monday, April 18, 2022 at 8:07:58 PM UTC-4, palli...@gmail.com wrote:
> Ricky the IDIOT wrote:
> ==================
> > >>
> > > > Is there some fundamental reason why renewable power sources on the grid can't
> > > > provide the equivalent of "inertia", to stabilize the grid?
> > > >
> > > > It seems to me the only issue is normally renewable power sources are optimized to
> > > > provide the maximum power possible, so if the grid frequency slows (because there
> > > > is less power sourced than the power drained), renewable power generation is already maxed out.
> > > ** What happens now is that inverters feeding the grid *track* the existing frequency - cos they are minor players in supplying the load.
> > > But what if that were not the case, they became the majority suppliers and and instead were locked to a central clock ?
> > >
> > > Rotating machines would then follow them.
> >
> > That's a weird thing to say. If the "inverters" were locked to a central clock and driving the grid,
> > rotating generators would be no different than they are now, following the grid.
> ** Whaaaaaaatttttt ??????
>
> Insane, retarded crap.

Ah, Phil speak for he doesn't understand.

--

Rick C.

+- Get 1,000 miles of free Supercharging
+- Tesla referral code - https://ts.la/richard11209

Re: Grid Stability and Renewable Power

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Subject: Re: Grid Stability and Renewable Power
From: gnuarm.d...@gmail.com (Ricky)
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 by: Ricky - Tue, 19 Apr 2022 02:08 UTC

On Monday, April 18, 2022 at 8:28:18 PM UTC-4, jeff.li...@gmail.com wrote:
> On Mon, 18 Apr 2022 14:51:38 -0700 (PDT), Phil Allison
> <palli...@gmail.com> wrote:
>
> >Ricky wrote:
> >===========
> >>
> >> Is there some fundamental reason why renewable power sources on the grid can't
> >> provide the equivalent of "inertia", to stabilize the grid?
> >>
> >> It seems to me the only issue is normally renewable power sources are optimized to
> >> provide the maximum power possible, so if the grid frequency slows (because there
> >> is less power sourced than the power drained), renewable power generation is already maxed out.
> >
> >** What happens now is that inverters feeding the grid *track* the existing frequency - cos they are minor players in supplying the load.
> > But what if that were not the case, they became the majority suppliers and and instead were locked to a central clock ?
> >
> > Rotating machines would then follow them.
> >
> >...... Phil
> Synchronizing grid tied inverters and generators using GPS clocks and
> GPS disciplined oscillators is a common topic for green research
> papers. For example:
> "How Microsynchrophasors Could Keep Solar-Saturated Grids Stable"
> <https://www.greentechmedia.com/articles/read/How-Microsynchrophasors-Could-Keep-Solar-Saturated-Grids-Stable>
>
> The fun begins if the grid frequency slows down a little due to a
> decrease in source supply or an increase in load. A short while
> later, the generators are adjusted to bring everything back to exactly
> 50 or 60Hz. However, that's not good because the frequency also needs
> to be adjusted to compensate for the time lost during the power sag.
> Otherwise, all the power line driven synchronous motor clocks would
> runs slow. So, the frequency of the entire grid needs to be increased
> slightly until the lost milliseconds are recovered, when it is now
> safe to return to exactly 50 or 60Hz. This explains the basics of how
> it's done:
> <https://www.mainsfrequency.com/gridtime.php>
> Notice that the example shows that Swiss time was 160 seconds behind
> UTC in June 2013. At 50Hz, that's
> 160sec * 50cycles/sec = 8,000
> clock cycles that need to added to the grid for grid time to catch up
> with UTC time. Looking at the graph (blue line), time still hasn't
> caught up 6 months later.
>
> Bottom line is that synchronizing grid tied inverters is certainly
> possible, but isn't quite as simple as it might initially appear.

I don't know about Switzerland, but in the US, didn't they throw in the towel on supporting synchronous clocks? I think that happened over 10 years ago. Maybe I was misinformed. I found an article at the IEEE from 2011 about a year long experiment where they were going to stop correcting the grid to see how many people complained. I didn't find anything about the result.

--

Rick C.

++ Get 1,000 miles of free Supercharging
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Re: Grid Stability and Renewable Power

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From: jef...@cruzio.com (Jeff Liebermann)
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Subject: Re: Grid Stability and Renewable Power
Date: Mon, 18 Apr 2022 21:23:27 -0700
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 by: Jeff Liebermann - Tue, 19 Apr 2022 04:23 UTC

On Mon, 18 Apr 2022 19:08:01 -0700 (PDT), Ricky
<gnuarm.deletethisbit@gmail.com> wrote:

>I don't know about Switzerland, but in the US, didn't they throw in the towel on supporting synchronous clocks? I think that happened over 10 years ago. Maybe I was misinformed. I found an article at the IEEE from 2011 about a year long experiment where they were going to stop correcting the grid to see how many people complained. I didn't find anything about the result.

This is probably the 2011 paper about the test:
<https://phys.org/news/2011-06-power-grid-disrupt-clocks.html>

Reports started to appear a few years later. However, I can't tell if
the 1 year test was actually performed. This report looks like it was
done using historical data from a power line frequency monitoring
network:
"Impacts of Power Grid Frequency Deviation on Time
Error of Synchronous Electric Clock and Worldwide
Power System Practices on Time Error Correction"
<https://mdpi-res.com/d_attachment/energies/energies-10-01283/article_deploy/energies-10-01283.pdf>
"On the other hand, the identification results present that up to the
end of 2016, many electric utilities around the world, especially in
North America and Europe, provided the TEC service to periodically
remove the accumulative time error of synchronous electric clocks."

This CAISO document indicates that TEC (time error correction) was
active in western USA at least up to 2019:
<https://www.caiso.com/documents/rc0220.pdf>

This 2021 document indicates that in the event of an emergency, time
error correction can be temporarily suspended until things sort
themselves out:
<https://www.caiso.com/Documents/4420.pdf>

Kinda looks like TEC is currently alive and well, at least for some
grid operators.

Drivel: Old technology doesn't completely die out, even after several
generations of superior technologies. For example:
<https://www.google.com/search?q=swimming+pool+timer&tbm=isch>

--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

Re: Grid Stability and Renewable Power

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Newsgroups: sci.electronics.design
Subject: Re: Grid Stability and Renewable Power
Date: Tue, 19 Apr 2022 15:53:36 -0000 (UTC)
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 by: Bertrand Sindri - Tue, 19 Apr 2022 15:53 UTC

Jeff Liebermann <jeffl@cruzio.com> wrote:
> The fun begins if the grid frequency slows down a little due to a
> decrease in source supply or an increase in load. A short while
> later, the generators are adjusted to bring everything back to exactly
> 50 or 60Hz. However, that's not good because the frequency also needs
> to be adjusted to compensate for the time lost during the power sag.

Time error correction is no longer done in the US after 2017:

https://www.usatoday.com/story/money/economy/2018/05/17/clocks-may-change-power-grid-maintenance-rule/619864002/

"... so last year, the correction part was quietly eliminated by the
Federal Energy Regulatory Commission."

https://www.balch.com/insights/publications/2017/01/www.balch.com/-/media/erl-blog/fercordersrulesdelegated-order-approving-retirement-for-reliability-standard-bal0040.pdf

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From: jef...@cruzio.com (Jeff Liebermann)
Newsgroups: sci.electronics.design
Subject: Re: Grid Stability and Renewable Power
Date: Tue, 19 Apr 2022 10:20:06 -0700
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 by: Jeff Liebermann - Tue, 19 Apr 2022 17:20 UTC

On Tue, 19 Apr 2022 15:53:36 -0000 (UTC), Bertrand Sindri
<bertrand.sindri@yahoo.com> wrote:

>Jeff Liebermann <jeffl@cruzio.com> wrote:
>> The fun begins if the grid frequency slows down a little due to a
>> decrease in source supply or an increase in load. A short while
>> later, the generators are adjusted to bring everything back to exactly
>> 50 or 60Hz. However, that's not good because the frequency also needs
>> to be adjusted to compensate for the time lost during the power sag.
>
>Time error correction is no longer done in the US after 2017:
>
>https://www.usatoday.com/story/money/economy/2018/05/17/clocks-may-change-power-grid-maintenance-rule/619864002/
>
>"... so last year, the correction part was quietly eliminated by the
>Federal Energy Regulatory Commission."
>
>https://www.balch.com/insights/publications/2017/01/www.balch.com/-/media/erl-blog/fercordersrulesdelegated-order-approving-retirement-for-reliability-standard-bal0040.pdf

Thanks. The above document seems to suggest that it's only replacing
one standard (BAL-003-xxx) with a new and improved version
(BAL-004-0). Without reading the standard, I can't tell if TEC (time
error correction) is still being performed using a new and improved
TEC procedure or standard. I said "seems to suggest" because I'm
having difficulties decoding the legalese.

Quoting:
NERC explains that since Reliability Standard
BAL-004-0 became effective, improvements have been
made to mandatory Reliability Standards (such as
the development of Reliability Standards BAL-003-1.1
and BAL-001-2 and the Interconnection Reliability
Operations and Coordination (IRO) Standards) that
help ensure continued adherence to frequency
approximating 60 Hertz over long-term averages and
make Reliability Standard BAL-004-0 redundant.

Note that "continued adherence to frequency..." indicates that
something is being done to maintain a "long-term average" 60Hz. If
synchronous clocks were not an issue, there would be no need for this
"long-term average". Also, just because it is no longer a regulatory
requirement to maintain clock sync doesn't prevent the utilities from
doing it anyway possibly because no utility wants to be first to be
identified as causing a problem with some forgotten device due to an
oversight. Also note that compliance to this reliability standard is
voluntary, not mandatory:
<https://www.nerc.com/pa/Stand/Pages/SARUrgentActionBAL004.aspx>
"Time Monitor is a voluntary service and, therefore, should not be
penalized for non compliance." Note that this was done in 2008.

--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

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 by: Phil Allison - Tue, 19 Apr 2022 22:15 UTC

jeff.li...@gmail.com wrote:
==================
>
> >** What happens now is that inverters feeding the grid *track* the existing frequency - cos they are minor players in supplying the load.
> > But what if that were not the case, they became the majority suppliers and and instead were locked to a central clock ?
> >
> > Rotating machines would then follow them.
> >
> >...... Phil
>
> The fun begins if the grid frequency slows down a little due to a
> decrease in source supply or an increase in load. A short while
> later, the generators are adjusted to bring everything back to exactly
> 50 or 60Hz.
>

** That is not what really happens.

The supply frequency is in constant, slow oscillation around the nominal 50 or 60Hz.
Anyone with a period counter or a scope in X-Y mode can verify this.

Excursions are limited to about +/- 0.1 Hz and take several minutes per cycle.
There are web pages that show this in real time too.

In any case, the millions of mostly electronic clocks that rely on this frequency cannot be trusted due to the high probability of local outages and tripping circuit breakers.

....... Phil

Re: Grid Stability and Renewable Power

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Subject: Re: Grid Stability and Renewable Power
From: gnuarm.d...@gmail.com (Ricky)
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 by: Ricky - Tue, 19 Apr 2022 22:53 UTC

On Tuesday, April 19, 2022 at 6:15:55 PM UTC-4, palli...@gmail.com wrote:
> jeff.li...@gmail.com wrote:
> ==================
> >
> > >** What happens now is that inverters feeding the grid *track* the existing frequency - cos they are minor players in supplying the load.
> > > But what if that were not the case, they became the majority suppliers and and instead were locked to a central clock ?
> > >
> > > Rotating machines would then follow them.
> > >
> > >...... Phil
> >
> > The fun begins if the grid frequency slows down a little due to a
> > decrease in source supply or an increase in load. A short while
> > later, the generators are adjusted to bring everything back to exactly
> > 50 or 60Hz.
> >
> ** That is not what really happens.
>
> The supply frequency is in constant, slow oscillation around the nominal 50 or 60Hz.
> Anyone with a period counter or a scope in X-Y mode can verify this.
>
> Excursions are limited to about +/- 0.1 Hz and take several minutes per cycle.
> There are web pages that show this in real time too.
>
> In any case, the millions of mostly electronic clocks that rely on this frequency cannot be trusted due to the high probability of local outages and tripping circuit breakers.

So, mismatches in generation and load do not result in a change in frequency? That's an interesting idea. So where does rotational inertia come in?

--

Rick C.

--- Get 1,000 miles of free Supercharging
--- Tesla referral code - https://ts.la/richard11209

Re: Grid Stability and Renewable Power

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From: '''newsp...@nonad.co.uk (Martin Brown)
Newsgroups: sci.electronics.design
Subject: Re: Grid Stability and Renewable Power
Date: Wed, 20 Apr 2022 09:49:30 +0100
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 by: Martin Brown - Wed, 20 Apr 2022 08:49 UTC

On 18/04/2022 15:43, Ricky wrote:
> On Monday, April 18, 2022 at 5:45:31 AM UTC-4, Martin Brown wrote:

>> The calculation that wasn't allowed for in the UK is that with
>> domestic generation on home roofs and on a sunny day when you shed
>> "load" you will also shed a whole bunch of local solar PV
>> generation as well.
>
> Let's leave the small, domestic systems out of the conversation.

But they are critical to understanding one of the key modes of failure
that took down so much of the UK grid. Roughly 2% of roofs have solar
panels on each producing 4kW in good sunlight and at a time when average
household load is about 200W so per thousand homes you have:

200kW load and 80kW local solar PV. The system tried to stabilise itself
by shedding 1MW of load but at the same time it lost 400kW of local
generation as well and so had to keep on dropping chunks off supply. It
was always behind the curve at every step of the way. The algorithm
expected to overshoot and then be able to reconnect. It didn't happen.

As the number of homes with solar PV increases it becomes harder and
harder to ignore this effect at >5% they become net exporters at least
when the sun is shining.

> The particular point someone was making was that no inverters used
> with wind power (or solar farms) has the ability to help stabilize
> the grid, because there is no rotating inertia. It was not claimed
> that this was not possible, but it was implied by pointing out no one
> had done this yet and it would be a very useful feature.

There is some rotating inertia in the spinning wind turbine blades but
nothing like as much as there is in a big mechanical steam turbine but
enough to keep going provided that you allow the frequency to drift.

> Seems to me it would require some way of increasing the power output,
> which means the facility has to run below optimal efficiency to have
> anything in reserve.

One way to build some resilience is to have local battery storage that
is immediately available to boost output when there is a sudden change
in load. US & Australia has a fair sized one to control peak loading.

https://www.bbc.com/future/article/20201217-renewable-power-the-worlds-largest-battery

UK has one but it is a complete toy and wasn't in the right place to do
any good last time. UK has a structural problem in that most power is
generated in the north and shipped down to the south to be used. The
upshot of this if they lose either of the big N-S EHT supergrid lines
then the south is very short of electricity and something has to give.

Pumped storage reservoirs are our most effective load balancing tool for
immediate generation of more power. Routine balancing is done by
adjusting power delivered the ultimate sink loads (on very favourable
intermittent tariffs). Unfortunately if you have already asked them to
power down you don't have that option (as has occurred some winters).

> The advantage of natural inertia, is the continuous nature. As much
> energy as is needed is available if you are able to tolerate the
> reduction in frequency. Of course, there is a limit to the inertia
> available, but it seems to do the job pretty well in most cases,
> while currently we seem to get nothing from solar and wind power
> facilities.

You can still simulate inertia by allowing the inverter to drift further
off frequency than the standard rules would normally allow. Something
like this tweak has been done to avoid quite so much chaos next time.

I presume that they have fixed the assumptions that caused the load
shedding algorithms to misjudge how much *absolute* load they would
have to drop to obtain a net saving of 1MW in future. It was a pretty
catastrophic mode of cascade systems failure for what should have been a
routine lightning strike with local cutout protection and recovery.

I don't think it would be such a problem in the USA since peak solar PV
output and peak domestic aircon requirements more or less balance it
out. In the UK there is hardly any domestic aircon so that in sunny
weather most of what is generated by domestic PV is exported to the grid
(especially in the late afternoon).

A stupid feature of the UK's "green" feed in tariff makes it cost
effective to have solar PV power and turn it into domestic hot water!
After market gizmos abound to do this automatically. You are deemed to
export half of what you generate irrespective of using it or not.

--
Regards,
Martin Brown

Re: Grid Stability and Renewable Power

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From: '''newsp...@nonad.co.uk (Martin Brown)
Newsgroups: sci.electronics.design
Subject: Re: Grid Stability and Renewable Power
Date: Wed, 20 Apr 2022 09:53:02 +0100
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 by: Martin Brown - Wed, 20 Apr 2022 08:53 UTC

On 19/04/2022 23:53, Ricky wrote:
> On Tuesday, April 19, 2022 at 6:15:55 PM UTC-4, palli...@gmail.com wrote:
>> jeff.li...@gmail.com wrote:
>> ==================
>>>
>>>> ** What happens now is that inverters feeding the grid *track* the existing frequency - cos they are minor players in supplying the load.
>>>> But what if that were not the case, they became the majority suppliers and and instead were locked to a central clock ?
>>>>
>>>> Rotating machines would then follow them.
>>>>
>>>> ...... Phil
>>>
>>> The fun begins if the grid frequency slows down a little due to a
>>> decrease in source supply or an increase in load. A short while
>>> later, the generators are adjusted to bring everything back to exactly
>>> 50 or 60Hz.
>>>
>> ** That is not what really happens.
>>
>> The supply frequency is in constant, slow oscillation around the nominal 50 or 60Hz.
>> Anyone with a period counter or a scope in X-Y mode can verify this.
>>
>> Excursions are limited to about +/- 0.1 Hz and take several minutes per cycle.
>> There are web pages that show this in real time too.

In general it often tends to run consistently slow when the loads are at
highest peak (like evening meal time in the UK) or peak afternoon aircon
load in the USA and consistently fast in the middle of the night.

The latter used to be a nuisance for some old school telescope drives
that were mains synchronous motor based. When you are tracking to arc
second precision the mains just isn't accurate enough. They moved to
quartz crystal references or servo with autoguider pretty much as soon
as the technology became available. Much less work for the observer.

>> In any case, the millions of mostly electronic clocks that rely on this frequency cannot be trusted due to the high probability of local outages and tripping circuit breakers.

Quite a lot of traffic lights still rely on it too.

The advent of cheap VLF time modules has made it much less of a problem.
Mains powered synchronous motor based kit has all but died out now. But
there are plenty of legacy traffic lights that need resetting after a
long powercut (since they tend to resume from whatever time they were at
when the power goes down). A few minutes is fairly harmless but a few
hours and the rush hour traffic flows end up in total chaos.
>
> So, mismatches in generation and load do not result in a change in frequency? That's an interesting idea. So where does rotational inertia come in?
>
That isn't what he said.

They have always allowed the mains frequency to drift slightly with time
to accommodate minor imbalances in the load at peak times. Heavy load
means lower frequency and lighter loads the allow it to run a bit fast.
It hunts slowly around the nominal frequency since if they predict that
load will increase they will bring more generation onstream.

To keep dead reckoning mains powered clocks based on synchronous motors
accurate they increase the frequency slightly when the loads are lowest
in the middle of the night. The average mains frequency over 24 hours
is held to very high precision linked back to atomic time standards.
(from what others have said it seems the USA have relaxed this rule)

Network phase in the UK is relatively well defined since 800km << 6000km
(one wavelength at 50Hz).

But in the USA where network distances are much greater the network
phase must be locally determined. eg. SF to NY is ~4000km which is a
very non-negligible fraction of a 60hz wavelength of 5000km.

--
Regards,
Martin Brown

Re: Grid Stability and Renewable Power

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Subject: Re: Grid Stability and Renewable Power
From: palliso...@gmail.com (Phil Allison)
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 by: Phil Allison - Wed, 20 Apr 2022 09:44 UTC

Martin Bullshit LIAR Brown wrote:

=============================
>
> >>>
> >>>> ** What happens now is that inverters feeding the grid *track* the existing frequency - cos they are minor players in supplying the load.
> >>>> But what if that were not the case, they became the majority suppliers and and instead were locked to a central clock ?
> >>>>
> >>>> Rotating machines would then follow them.
> >>>>
> >>>> ...... Phil
> >>>
> >>> The fun begins if the grid frequency slows down a little due to a
> >>> decrease in source supply or an increase in load. A short while
> >>> later, the generators are adjusted to bring everything back to exactly
> >>> 50 or 60Hz.
> >>>
> >> ** That is not what really happens.
> >>
> >> The supply frequency is in constant, slow oscillation around the nominal 50 or 60Hz.
> >> Anyone with a period counter or a scope in X-Y mode can verify this.
> >>
> >> Excursions are limited to about +/- 0.1 Hz and take several minutes per cycle.
> >> There are web pages that show this in real time too.
>
> In general it often tends to run consistently slow when the loads are at
> highest peak (like evening meal time in the UK) or peak afternoon aircon
> load in the USA and consistently fast in the middle of the night.

** So you have never checked the *actual frequency* or followed on-line pages that give a 24/7 readout.
Your whole bullshit is just fucking made up.

LIKE EVERY POST YOU HAVE EVER MADE !!
-----------------------------------------------------------------------------

> >> In any case, the millions of mostly electronic clocks that rely on this frequency
> cannot be trusted due to the high probability of local outages and tripping circuit breakers.
>
> Quite a lot of traffic lights still rely on it too.

** FFS what a fucking ridiculous red herring !!!

> > So, mismatches in generation and load do not result in a change in frequency?
> That's an interesting idea. So where does rotational inertia come in?
> >
> That isn't what he said.

** At least you got that one right.

Ricky is a total fucking, bullshitting ASD fucked IDIOT .
So are YOU !!!

> They have always allowed the mains frequency to drift slightly with time
> to accommodate minor imbalances in the load at peak times.

** Bullshit.

> Heavy load means lower frequency

** Bullshit.

> and lighter loads the allow it to run a bit fast.

** Bullshit.

> It hunts slowly around the nominal frequency since if they predict that
> load will increase they will bring more generation onstream.

** Bullshit.

> To keep dead reckoning mains powered clocks based on synchronous motors
> accurate they increase the frequency slightly when the loads are lowest
> in the middle of the night.

** Bullshit.

...... Phil

Re: Grid Stability and Renewable Power

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Subject: Re: Grid Stability and Renewable Power
Date: Wed, 20 Apr 2022 06:35:16 -0700
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 by: Don Y - Wed, 20 Apr 2022 13:35 UTC

On 4/20/2022 1:53 AM, Martin Brown wrote:

> They have always allowed the mains frequency to drift slightly with time to
> accommodate minor imbalances in the load at peak times. Heavy load means lower
> frequency and lighter loads the allow it to run a bit fast. It hunts slowly
> around the nominal frequency since if they predict that load will increase they
> will bring more generation onstream.
>
> To keep dead reckoning mains powered clocks based on synchronous motors
> accurate they increase the frequency slightly when the loads are lowest in the
> middle of the night. The average mains frequency over 24 hours is held to very
> high precision linked back to atomic time standards.

In the early-mid 70's, I wanted a clock that wouldn't have to deal with
the silly time changes so designed one around a 10MHz TCXO that we happened
to use in one of our products. I was chagrined to discover it was off several
seconds each month -- until I looked at the tolerance on the oscillator
(a few PPM).

As I couldn't step *up* to an OCXO (too much power required to keep it
operating through power outages), I looked to the mains as an alternate time
source ("how can *regular* clocks keep such good time?"). Eventually,
replacing all of the discrete logic with a processor I could "watch" the
mains frequency vary (against the stable TCXO) over the course of a day.
I.e., the mains-derived time had short-term stability problems but
long-term accuracy.

So, I fell upon the idea of using the mains frequency to tweek the TCXO's
notion of time. Then, realized the TCXO was essentially unnecessary;
any time source of sufficient short term stability could suffice -- if I
could *measure* that frequency against the mains over VERY long intervals.

Subsequent clocks have been built around cheap watch crystals/RTCs and
keep remarkably good time (much better than an undisciplined PC). I now
discipline my NTP server with such a source (I don't care if my PCs are
"off" by N seconds -- as long as they are ALWAYS off by N seconds -- as
this lets me operate without a GPS signal *or* routing them!)

> (from what others have said it seems the USA have relaxed this rule)

I'd been told that was *supposed* to happen. But, haven't seen any practical
consequences on any of my mains-disciplined clocks.

> Network phase in the UK is relatively well defined since 800km << 6000km (one
> wavelength at 50Hz).
>
> But in the USA where network distances are much greater the network phase must
> be locally determined. eg. SF to NY is ~4000km which is a very non-negligible
> fraction of a 60hz wavelength of 5000km.

There is a group that (informally?) monitors this nationwide, here (US):
<https://en.wikipedia.org/wiki/FNET>
I question how reliable their phase measurements are, given that they are
looking at "consumer" distributions and not the "backbone" of the
power network. (but, *frequency* observations should be dead to nuts)

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