early implementations of simplified AC load flow in energy system optimization frameworks

[Robbie Morrison]

Hello all

I am looking for some historical context.

The first energy (as opposed to electricity) system optimization frameworks treated electricity as any other commodity (like coal) — albeit non‑storable.  For instance, MARKAL and derivatives.  Also deeco in 1995.

Later came nodal pricing (aka locational marginal pricing) methodologies that embedded simplified AC load flow to underpin these then new markets.  An early example was reported as Alvey et al (1998) for New Zealand as introduced in 1996 (I attended some of lead‑up public consultation for this revised non‑copper‑plate market).

Simplified AC load flow (aka power flow) usually assumes no voltage drop and voltage angles to about 45° (Motto et al 2002).  The methodology is sometimes described as the "DC approximation".

By my very rough reckoning, generalized energy system projects with AC load flow would include: xeona circa 2012, GenX circa 2017, and PyPSA circa 2020 or later (first public commit 0.3.0 on 14-Jul-2020, was PyPSA just for power systems back then?).  My apologies in advance for omitting or misrepresenting key frameworks.

many thanks, Robbie

PS: It could be worth collecting some of the early history of open energy system modeling on a wiki or similar?  Key milestones could be noted as well.  Mark Howells (from OSeMOSYS) once suggested this to me.

References

Alvey, Trevor, Doug Goodwin, Xingwang Ma, Dan Streiffert, and David Sun (1998). "A security-constrained bid-clearing system for the New Zealand wholesale electricity market". IEEE Transactions on Power Systems. 13 (2): 340–346. doi:10.1109/59.667349.

Motto, Alexis L, Francisco D Galiana, Antonio J Conejo, and José M Arroyo (2002). "Network-constrained multiperiod auction for a pool-based electricity market". IEEE Transactions on Power Systems. 17 (3): 646–653. ISSN 1558-0679. doi:10.1109/MPER.2002.4312289.

▢

-- 
Robbie Morrison
Address: Schillerstrasse 85, 10627 Berlin, Germany
Phone: +49.30.612-87617

[Tom Brown]

Hi Robbie,

The first public release of PyPSA was on 27th Jan 2016, v0.3.0:

https://pypsa.readthedocs.io/en/latest/references/release-notes.html#v0-3-0-27th-january-2016

https://github.com/PyPSA/PyPSA/commit/6f214336f0d64e9061ec3a4a0c3afea3530fa016

Announcement to openmod:

https://groups.google.com/g/openmod-initiative/c/Yz7UyrKHaSw/m/4I6ZYfq-EgAJ

I think the date you have there was when I put it into the GitHub
release format thing.

This release was initially power-sector only, we added the "Link" for
generalised energy conversion a few months later, released July 2016

https://pypsa.readthedocs.io/en/latest/references/release-notes.html#v0-5-0-21st-july-2016

That was some fun archaeology...

Best,

Tom

On 23/05/2025 07:39, Robbie Morrison wrote:
> Hello all
>
> I am looking for some historical context.
>
> The first energy (as opposed to electricity) system optimization
> frameworks treated electricity as any other commodity (like coal) —
> albeit non‑storable.  For instance, MARKAL and derivatives. Also deeco
> in 1995.
>

> Later came nodal pricing <https://en.wikipedia.org/wiki/
> Electricity_market#Bid-based,_security-
> constrained,_economic_dispatch_with_nodal_prices> (aka locational

> marginal pricing) methodologies that embedded simplified AC load flow to
> underpin these then new markets.  An early example was reported as

> Alvey /et al/ (1998) for New Zealand as introduced in 1996 (I attended

> some of lead‑up public consultation for this revised non‑copper‑plate
> market).
>
> Simplified AC load flow (aka power flow) usually assumes no voltage drop

> and voltage angles to about 45° (Motto /et al/ 2002). The methodology is

> sometimes described as the "DC approximation".
>
> By my very rough reckoning, generalized energy system projects with AC
> load flow would include: xeona circa 2012, GenX circa 2017, and PyPSA
> circa 2020 or later (first public commit 0.3.0 on 14-Jul-2020, was PyPSA
> just for power systems back then?).  My apologies in advance for
> omitting or misrepresenting key frameworks.
>
> many thanks, Robbie
>
> PS: It could be worth collecting some of the early history of open
> energy system modeling on a wiki or similar?  Key milestones could be
> noted as well.  Mark Howells (from OSeMOSYS) once suggested this to me.
>
>
> References
>
> Alvey, Trevor, Doug Goodwin, Xingwang Ma, Dan Streiffert, and David Sun
> (1998). "A security-constrained bid-clearing system for the New Zealand

> wholesale electricity market". /IEEE Transactions on Power Systems/.
> *13* (2): 340–346. doi:10.1109/59.667349 <https://
> doi.org/10.1109/59.667349>.

>
> Motto, Alexis L, Francisco D Galiana, Antonio J Conejo, and José M
> Arroyo (2002). "Network-constrained multiperiod auction for a pool-based

> electricity market" <https://www.academia.edu/download/48811172/Network-
> Constrained_Multiperiod_Auction_20160913-25825-ta5ftq.pdf>. /IEEE
> Transactions on Power Systems/. *17* (3): 646–653. ISSN 1558-0679
> <https://www.worldcat.org/issn/1558-0679>. doi:10.1109/MPER.2002.4312289
> <https://doi.org/10.1109/MPER.2002.4312289>.
>
> ▢

>
> --
> Robbie Morrison
> Address: Schillerstrasse 85, 10627 Berlin, Germany
> Phone: +49.30.612-87617
>

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--
Tom Brown (he/him)
Professor of Digital Transformation in Energy Systems
Institute of Energy Technology
Technische Universität Berlin

Group website: https://www.tu.berlin/en/ensys
Personal website: https://nworbmot.org/

Visitor Address:
Einsteinufer 25 (TA 8)
10587 Berlin

[Berit Müller]

Hi Robbie,

I remember additionally ISI with the project “energy rich Japan” around 2003  (Harry Lehmann). With their own Model…(I don’t know the name)

I’m not sure how much load flow was implemented

@ISI colleagues: does this fit here?

Best

Berit

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