State Estimation Setup

[cavassiGE]

Hi! I would like tips and help with my setup for a state estimation.

I have a low voltage network with one transformer, using the "inner side" of the transformer components. I have reduced the components to just include the clients node, busbars, joints, and different cable types. The client nodes are also the points where real life measurements are being made (real life sensors). These measure the voltage which usually is around 230-240V. They also measure active and reactive power.

If it makes a difference, the graph can be seen in "graph.png".

Right now, I'm building the PowerGridModel object with these components:

input_data[ComponentType.node] = nodes
input_data[ComponentType.line] = lines
input_data[ComponentType.source] = source
input_data[ComponentType.sym_voltage_sensor] = sym_voltage_sensor
input_data[ComponentType.sym_power_sensor] = sym_power_sensor

The source, voltage sensor, and power sensor components are pretty much the same as the documentation. Should I consider adding loads? If so, how many? On which nodes? What values should they have?

I build the object and run the state estimation the same way as the documentation.

If my results could be useful, the most typical values can be seen in results.txt

Either my setup is wrong and I need to reconsider something from it. Or the constants I'm using are not accurate.

I'll also upload a file with the constants I'm using and their values

results.txt

config.py

[mgovers]

Hi @cavassiGE,

Thank you for your questions. Here is my attempt to answer them:

Should I consider adding loads? If so, how many? On which nodes? What values should they have?

Yes, you should add a load (resp. generator) at every location where you expect an energy consumer (resp. producer) - i.e., the same locations in which you would have a load if you were to run a power flow calculation. In your case, if my assumption is correct, that that would be at the red nodes.

However, you do not need to assign p_specified and q_specified, as the power consumption will be calculated from the sensor measurements. The reason you need to specify the loads is so that the Power Grid Model knows where consumption is happening. Without loads, the model thinks there is no consumption happening, so all estimated power flows are zero.

The rest of your setup seems to be OK.

I hope this helps. Please let us know how it goes!

[cavassiGE]

Thank you for your answer!

You are correct, the red nodes are where the voltage and active/reactive power is being measured. So having the loads here makes sense.

I have now added the sym_load components, which naturally changed the output. But the results are still not looking very good. The error tolerance need to be minimum 2e-1 for the estimation to be able to run, which I believe is way higher than wanted.

To give you as much context as possible, I'll share the file where I create the PowerGridModel object, as well as the config which is now slightly updated. I have tried tweaking some of the constants, but I'm afraid my physics knowledge are not good enough to know what a reasonable value is for most of them.

I'll also share the results, but since the data used as input is classified, I've had to round/remove/modify some of the output values. But the overall picture is still the same.

Not sure if these points are interesting, but some things to notice are:

• the extreme outliers (try ctrl+f and search for e+0X)
• all Lines have NaN on loading
• the source values does not look reasonable right?

I've added some TODOs in the code for things that I'm not sure about.

Thank you again!

graph_to_pgm.py

summary.txt

[mgovers]

Hi @cavassiGE,

I see that you specify u_measured in p.u. (per unit/natural units) instead of in Volt (sym_voltage_sensor["u_measured"][i] = float(row["voltage"]) / conf.LV_LN_VOLTAGE). This should probably be simply sym_voltage_sensor["u_measured"][i] = float(row["voltage"])

If that does not help, can you run a couple tests to see what is up?

1. I see that you add quite a lot of voltage sensors (while not necessarily an issue, it may hide other things). Can you please run an experiment in which you only add 1 single voltage sensor?
2. What happens if you change the measured_object_type from MeasuredObjectType.node to MeasuredObjectType.sym_load and also change the measured_object to the respective sym_load ID? This should at the very least make the active and reactive power values in the output sym_loads be correct.

[cavassiGE]

Changing the u_measured to Volts gives me a max deviation of around 3.35. I could raise the error tolerance and provide the new results if you'd like.

1. Single voltage sensor:

using p.u gave me a Max deviation of 110
using Volts gave me a Max deviation of 497
(15 iterations on both)

2. I suppose you mean MeasuredTerminalType because I can't find MeasuredObjectType. Same for .sym_load, I can only find .load.

I tried doing the ID changes without reverting from 1. and got that there were Not enough measurements available for state estimation. The total number of independent power sensors is not enough to make the grid observable.

Then I also tried changing the ID's with all the voltage sensors. with both p.u values and Volt.

Volt gave me a max deviation of 1.7
p.u was able to run and gave me a sym_load output seen here, again, rounded:
sym_load_result.txt

[cavassiGE]

I believe my code is fairly generic. Would it be possible to set up some small test environment with a simple graph and minimal voltage and P/Q datasets to determine whether the issue comes from my code or from my input data? @mgovers

[mgovers]

What you can do, is to create a personal or otherwise (maybe private?) repository and set up the needed code, data and tools there. We don't provide active support but we can have a quick look that way.

[cavassiGE]

Any recommendations on minimum amount of nodes/edges in the graph and voltage/PQ values to use?

[mgovers]

In general, the simpler, the better. That's called a minimal reproducible case. You can even try it out with one node, one source, one load and one voltage sensor and one power sensor. if that works as intended, you can then add one line, and then build up your grid.