Large power-systems for power-flow study
Large power-systems for power-flow study
(OP)
I have just been started on a research project which involves finding ways to speed up the solution time of the power-flow problem (see Wikipedia here) which is basically calculating voltages at each of the buses of a given power system.
I have a few data-sets like the standard IEEE power-flow test cases, mentioned here
However, these bus-systems are still very small. Is there any database (like the standard IEEE power-flow test cases mentioned above), but with a large number of buses. Large being on the order of 1000 to 10000 buses, or even larger.
If also there is some standard algorithm for generating a "fake" power system with an arbitrary number of buses, or standard technique to join say several IEEE 300 bus systems to make a larger network, that would also be helpful.
I have a few data-sets like the standard IEEE power-flow test cases, mentioned here
However, these bus-systems are still very small. Is there any database (like the standard IEEE power-flow test cases mentioned above), but with a large number of buses. Large being on the order of 1000 to 10000 buses, or even larger.
If also there is some standard algorithm for generating a "fake" power system with an arbitrary number of buses, or standard technique to join say several IEEE 300 bus systems to make a larger network, that would also be helpful.






RE: Large power-systems for power-flow study
RE: Large power-systems for power-flow study
RE: Large power-systems for power-flow study
Thanks for the reply.
Are you solving the power-flow problem on this network of 15000 buses?
If so, could you give me a rough estimate of the time it takes to do power-flow (i.e. finding voltages
at the non-slack buses) on your desktop.
Thanks
RE: Large power-systems for power-flow study
RE: Large power-systems for power-flow study
please see the following link:
http://www.wecc.biz/library/Pages/Powerflow%20Base...
"WECC Powerflow Base Cases are available to all members free of charge. Some Powerflow Base Cases are also available to non-members upon approval."
run a 15000 or more node power flow using pss/e or pslf takes less than 2 to 3 seconds. some cases take less than 1 second.
RE: Large power-systems for power-flow study
Aspen fault calculation are near instantaneous, however solving WECC powerflow cases using PowerWorld often takes a couple of seconds per case on my computer. Not too long if you are doing just one, but our contingency file includes 8000 contingencies. FERC/NERC seems to be pushing for real-time contingency tool to able to resolve the whole set of contingencies every 2 minutes.
RE: Large power-systems for power-flow study
There's no doubt that there are still incremental improvements in computational speed to be wrung out, but large scale power system analysis has long been one of the cutting edge fields in applied mathematics. In a 15k bus system there are theoretically 225E6 entries in the Z (or Y) matrix; and probably 224.9E6 of them are zero. I'm reasonably sure that no modern system analysis program, fault or load flow, spends any time to speak of looking at the zeros.
I'm reasonably certain that FERC/NERC are going to ultimately drive us to knowing the system state rather than estimating it (synchrophasors everywhere) and if you know the system state, the contingency analysis will be easier; someone will figure out a means to determine which contingencies are irrelevant for any given state and greatly reduce the number to be evaluated at any give time. If the OP wants to really get out in front, on the bleeding edge, it would be the math to determine which contingencies matter at any moment rather than trying to wring out another incremental improvement in sparse matrix analysis.
RE: Large power-systems for power-flow study
I had a couple of more questions.
I am pretty new to the field of power-flow studies so please
Please forgive me if they seem trivial, I am pretty new to the field of power-flow analysis myself.
1. In your experience what is the number of buses in the typical largest network on which power-flow is routinely performed?
2. Given ,say, a real n-bus system, how would one join an identical copy of this system to get a 2n bus system. Is it even reasonable to do so.
3. Say I have an algorithm to generate a sparse graph ie a graph where each vertex has the number of outgoing edges bounded by a small integer constant.
This graph can be used to represent the buses in a power-system. (Or better to say a power-system is a sprase graph)
Is there a way to assign reasonable real and reactive powers, basically obtaining a table like the IEEE 30 bus system here: http://www.ee.washington.edu/research/pstca/pf30/i...
Thanks.
RE: Large power-systems for power-flow study
Interesting project either way.
RE: Large power-systems for power-flow study
1. In your experience what is the number of buses in the typical largest network on which power-flow is routinely performed?
(I run a power flow case with appro. 25000 buses but my interest is only on about 1000 buses.)
2. Given ,say, a real n-bus system, how would one join an identical copy of this system to get a 2n bus system. Is it even reasonable to do so.
{I have encoutered above scenario only once in the past 20 years. It was because our area network was interconnected to the neighboring system with the new inter-ties. So our power flow cases have to include the neighboring system}
3. Say I have an algorithm to generate a sparse graph ie a graph where each vertex has the number of outgoing edges bounded by a small integer constant.
{I am not sure I fully understand your third question. I am guessing that you are trying to apply the sparse matrix methodology into the power flow program to increase the computation speed?
I am not aware that the PSS/E PSLF using sparse martix but in one of the EMTP typs of software they implemented the sparse matrix to get rid of the zeros first to improve the speed. Frankly speaking, off line power flow studies nowadays, engineers don't really care too much about the speed. However, in really time simulation, speed does play an important role. As far as I know most of the real time tools used in the control centers are using lousy algorithms to trade of the speed other than improve the matrix computation methodology.}
Hope it helps.
RE: Large power-systems for power-flow study
RE: Large power-systems for power-flow study
RE: Large power-systems for power-flow study
RE: Large power-systems for power-flow study
RE: Large power-systems for power-flow study
I checked the website you posted. Looks like Aspen has a powerful power flow tool. Too bad we did not purchase it. Otherwise I would like to try it and compare it with pss/e and pslf.
By the way, this gets nothing to do with WECC.
RE: Large power-systems for power-flow study
RE: Large power-systems for power-flow study
RE: Large power-systems for power-flow study
By accurate data, do you mean the accuracy of the non-linear solver itself, or the accuracy of the measurements
fed to the non-linear solver?
Because issues regarding non-convergence of the newton solver, or
occasional convergence to a bad solution do arise.
RE: Large power-systems for power-flow study
RE: Large power-systems for power-flow study
So, yes, you can get very large cases with little effort.
You might be surprised to know that speed of solution is NOT an issue for any modern Operations or Planning Engineer. The biggest hangup is the human being reading the thousands of results and deciding what it means. Having said that, I would suggest that the art of power system modeling is be no means a completed product and that any improvements are good in their own right.
In the real time environment power flows can be pounded out quickly enough...transient stability studies perhaps not as fast. The real issue is again processing the results into some actionable set of switching orders, etc for an operator.
The comments about bad data are always relevant...