Ray,
I think the version you sent should work. It is okay to do the updating
before calling pfsoln().
Regarding Niccolò’s second question about results being affected by
changing load which itself is not a meaurement, the answer is it depends. If
you change the load amount at non-generator bus, it should not affect the
state estimation results. However, if you change the load amount at
generator bus whose generation (Pg) is measured, the state estimation
results will change. It is because it will change the estimation error for
this Pg and therefore the total square of errors (Note that the state
estimator uses weighted lease square estimation method).
To give a simple example, if Pg measurement is 100MW and at the same bus
there is a 20MW load. Assume state estimation solution gives 98MW as
estimated Pg. Then, the net injection at this bus is 98-20=78MW. When you
change the load to 30MW and let's first assume the state estimation solution
doesn't change, the net injection will then remain the same as 78MW. Now,
the estimated Pg becomes 78MW+30MW=108MW. The Pg estimation error suddenly
increases from the original 2MW (=100-98) to 8MW (=100-108). State estimator
will be able to adjust the solution to further reduce the total square of
errors, resulting in a different SE solution.
Hope it helps.
Thanks,
Rui
Rui Bo
Ph.D, Principal Engineer, Senior Member IEEE
Regulatory and Economic Studies Department
Midcontinent Independent Transmission System Operator (MISO)
2985 Ames Crossing Rd
Eagan, MN 55121, USA
Cell: (865) 951-6639
Email: [email protected], [email protected]
Personal URL: https://sites.google.com/site/eeruibo/
-----Original Message-----
From: Ray Zimmerman
Sent: Tuesday, December 6, 2016 8:55 AM
To: MATPOWER discussion forum
Cc: [email protected]
Subject: Re: state estimation: active power not balanced in test cases
Thanks Rui.
Quick question … is there a reason to do the updating of the Pg and Qg
values after, rather than before calling pfsoln()? I’ve attached the
updated version I propose to include in v6.0.
And what about Niccolò’s second question regarding the results being
affected by system load rather than simply the measurements?
Thanks,
Ray
On Dec 6, 2016, at 2:35 AM, Ray Bo <[email protected]> wrote:
Hi Ray,
Sure I will take care of it.
Niccolò,
As I don't have 6.02b2 right now, I did a quick check on v5.1, and did see
the issue you brought up. The state estimation results are actually
correctly presented in the last section of the screen output, where you
can see the Pg2=0.3034 pu, Pg3=0.1336 pu. So the gen, load and losses are
balanced. The Pg2 and Pg3 values you see in the 'Generator Data' output
section are actually the default values from the 3-bus case, and appear to
be inbalanced with load. The reason Pg2 and Pg3 values do not get updated
in the 'Generator Data' output section is that, to output the power flow
solution in a nice format, I simply took advantage of the MATPOWER
function 'pfsoln' to update bus, gen, branch data structures to match
power flow solution. This function however only updates Pg for the slack
bus generator and not for the rest of the generators (because those are PQ
and PV buses and there is no need to do it).
To clean up the output to avoid such confusion, I have implemented a quick
fix for the issue by updating the Pg and Qg using state estimation
results. The code with the quick fix is attached. I haven't tested it
extensively. Please use it and let me know if you find it useful or if you
have additional questions. I can be reached at [email protected].
Thanks,
Rui
-----Original Message----- From: Ray Zimmerman
Sent: Monday, December 5, 2016 9:27 AM
To: Rui Bo
Cc: MATPOWER discussion forum
Subject: Re: state estimation: active power not balanced in test cases
Hi Rui and Niccolò,
The state estimation code was contributed by Rui Bo, so I’m not that
familiar with it. Rui, I was wondering if you might be able to address
Niccolò's questions.
Thanks,
Ray
On Dec 1, 2016, at 6:20 PM, Niccolò Citroni <[email protected]>
wrote:
Hallo, I'm new to matpower, using it for my master thesis.
I'm trying to figure out how the se program works, and running the
included test cases I noticed the following:
there is a big unbalance in active power in the network, for example in
the 3 bus case there are more than 380 MW of active power in excess,
considering generation, load, and losses. How is that possible?
Another thing: modifing the load i get different results runnning the se.
Why is that? shouldn't the state estimation be based only on the input
mesurements and the topology of the network? How has the load and
generator power anything to do with the se, when not included in the
mesurements? From what I know the power balance at each node should be a
result of the se, not part of the input data (when not as mesurements of
course).
I hope I've been clear enough.
I'm using version 6.0b2
Thankyou for the help and the program.
Niccolò Citroni
<run_se.m>
