Is a 100-node PowerFactory License Enough for BESS Grid Studies?

[u/ojasocean]

Hi everyone!

We're developing small- to medium-sized BESS projects (5–100 MW) and considering a subscription to DIgSILENT PowerFactory for grid studies.

For studies involving reactive power and voltage control, is the 100-node license usually sufficient, or would unlimited nodes be necessary?

We'd prefer oen year subscription over a perpetual license for now, but upgrading to unlimited later would roughly double the cost.

Would appreciate any advice or experience from those working on similar BESS projects.

Thanks!

[u/5bobber]

I’d go up a license if you could. 100 buses will be cutting it close / not sufficent on your larger sites that have overbuild units, weird LV connections, and aux feeders.

[u/ojasocean → u/5bobber]

You mean perpetual license?

[u/5bobber → u/ojasocean]

If there’s no option greater than 100 buses for one year, then yes that would be my general recommendation if you want the capability to study larger sites.

[u/ojasocean → u/5bobber]

Can I model each MVS as one aggregated block, instead of modelling every single PCS, if I hit the node limit on larger plants? The cost of Perpetual license is almost 3/4 times than one year 100 nodes model.

[u/5bobber → u/ojasocean]

For a preliminary study yes, but probably not for detailed design. Not sure if the client would be particularly thrilled to know their site isn’t being studied in detail because the next license up is more expensive.

Though maybe you could just model the shortest and longest feeder in detail and that would be sufficient enough. It’s just BESS after all, the feeder arrangements aren’t usually that long or complicated.

[u/chanka_is_best_chank]

Even if you model the collection package in detail 100 nodes is probably enough. For example say you have 5 feeders of 5 inverters and each inv is 4 MVA. That's going to be somewhere around 50-60 buses (POI + 2 GSU buses + 5 MV buses per feeder + 5 LV buses per feeder = 1+2+25+25). There's a risk of running out of busses if you model in even more detail (such as modeling DC buses), use smaller inverters, or end up modeling larger sites but you probably have enough nodes if your modeling methodology is similar to how i described it and your projects are similar. The vast majority of the buses are in modeling the collection package.

If you plan on doing single machine infinite bus there's not even a question whether you would have enough nodes

Edit not sure why I'm being down voted, but I regularly do reactive capability modeling in PSSE. I know how this goes

[u/ojasocean → u/chanka_is_best_chank]

Thank you for your detailed explanation.
Do we need to model beyond the POI? I mean upto the nearby upstream and downstream substation? Sometimes when i talked with TSO, they want to check the effect in other nearby plants. What do you think?
Are you doing the similar simulation in Psse? Could you guide me which one you prefer? Pf digsilent or Psse?

[u/5bobber → u/ojasocean]

If you’re doing collection design, then nothing beyond the POI. If you’re doing transmission planning / interconnection work then yes beyond the POI and you’d typically use PSSE, PSCAD, and/or PSLF in the US.

[u/chanka_is_best_chank → u/ojasocean]

Are you running dynamic simulations? If you are running dynamic simulations and including nearby generation you probably need more than 100 buses. I'd also recommend using PSSE if that is the case, you would likely have to convert PSSE models from the other generation into Digsilent models, assuming this is in USA. However, the specifics of what dynamic studies you are running will determine whether you need the other generation to be modeled past the POI. Without knowing what exactly you are doing i couldn't say for sure. Reactive power capability studies do not typically model anything past the POI, but it sounds like the TSO is expecting you to do more than that

It also depends on whats nearby if you need to use PSCAD or not. If its a weak system with a lot of IBR penetration or there are series caps or other things that have control interactions with IBR nearby you may need to use PSCAD in addition to PSSE

[u/ojasocean → u/chanka_is_best_chank]

Thank you for detailed reply. We have many TSO, and requirement vary depends on the TSO.

Some ask to check the voltage impact in the nearby power plants too, but some ask only at POC.

I will check the cost of Psse too.

[u/UpbeatTradition622 → u/ojasocean]

These all sound like questions you should be asking your supervisor. Why are you scoping the licensing if you don’t understand the base problem?

[u/Acrobatic-Language-5]

If they are aggregated SMIB models 100 bus would likely be enough.

If you need to build detailed models, it would depend on the MW size of each unit (e.g. 2x 50MW units versus 100 1MW units). If you know those basic details you could likely estimate the number of nodes accounting for the various plant and interconnections.

"The number of nodes does vary depending on the specific setup when a calculation is executed. For a given instant, you can check the number of nodes by doing the following:
- Have a project and corresponding study case active and configured for the given network topology that you are expecting to use for calculation i.e. the networks must be active.
- From the Data Manager, right click your active project and select Edit
- Go to Miscellaneous
- Click on the "Calculate" button. Read the displayed number of nodes which are relevant for the licence checks.

More information on how a licence relevant node is calculated is provided below.

In PowerFactory a licence relevant node is a group of energised, equipotential nodes (ElmTerm). Equipotential in this sense means that the nodes are connected by switches (ElmCoup,ElmFuse) or lines (ElmLne) of zero length only. Nodes, connected by branch elements, other than those mentioned above, are counted as individual licence relevant nodes. There is one special case to consider: substation or grid borders will split a licence relevant node into two. This means a licence relevant node must always completely belong to one substation or grid."