Re: convergence problem in runpf.
Mirish,
I couldn't help notice that you're building this model from scratch (well,
from a database) and you mentioned ***To make the problem simple I used
all buses as PQ buses except one slack bus*. This actually makes it
harder to converge, unless you have *very* accurate data on what the
reactive injections Q (on generator buses) should be.
May I suggest a different, incremental approach:
1. Start by keeping all generator buses you can as PV, instead of PQ.
They will help holding up the voltage profile. After all, a PV node is a
slack bus in what regards the reactive power injection.
2. For the loads, start by zeroing out PD (real power demand), but
keeping QD (reactive demand)
3. For generators, set the scheduled PG to zero
4. For lines transformers, zero out the resistance R
5. The resulting network will be a purely reactive power model. Now
run a powerflow. If this doesn't have a feasible powerflow solution, it is
because some branches have an X parameter that is too large (or
equivalently, some load QD is too large). Ramp down the profile of QD
until you see convergence.
6. Look at the resulting Q flows across branches, and try to detect
anomalously large values (i.e. clear outliers). They will help you uncover
values of X that may be wrong (too large). Also, keep an eye on negative X
coming from equivalents such as 3-winding transformers; they may also be
wrong.
7. Once you get that working, ramp up the values of PD on loads and PG
on generators (keeping an eye on the swing's resulting PG, in order to
redistribute big excesses).
8. Finally ramp up the resistance on lines.
The whole idea is based on the fact that, for transmission networks (lines
with RX), the reactive flows are like the backbone on which real power
flows can sort of ride on. Get a healthy backbone first, and then you
can start transporting real power.
Hope it helps,
--
Jose L. Marin
Gridquant España SL
Grupo AIA
On Wed, Aug 12, 2015 at 2:36 AM, Mirish Thakur mirishtha...@gmail.com
wrote:
Dear Mr.Shree,
Thank you very much for your help. As per your suggestion and FAQ I tried
to find out the problems.
The results I got-
1) Fast-decoupled power flow did not converge in 30 iterations.
2) By following http://www.pserc.cornell.edu/matpower/#pfconvergence I
tried to runcpf to get good initial guess and i got results like
step 1 : lambda = 0.084, corrector did not converge in 10 iterations.
Where lambda is 1 and for reducing steady state loading limitation I
reduced demand less than 60 % which also failed to converge the power flow.
3) Also I tried to run an optimal power flow according to Dr. Ray's
explanation given in following link-
*https://www.mail-archive.com/search?l=matpower-l@cornell.eduq=subject:%22Re%5C%3A+%5C%5BMatpower%5C%5D+3500+bus+simulation%22o=newest
https://www.mail-archive.com/search?l=matpower-l@cornell.eduq=subject:%22Re%5C%3A+%5C%5BMatpower%5C%5D+3500+bus+simulation%22o=newest*
but got the results like-
MATPOWER Version 5.1, 20-Mar-2015 -- AC Optimal Power Flow
MATLAB Interior Point Solver -- MIPS, Version 1.2, 20-Mar-2015
(using built-in linear solver)
itobjective step size feascond gradcond compcond
costcond
-
0 1200199.7 2.41677 0.71 536.762
0
1 946197.39 15.531 1.3682 1.75871 525.914
0.209885
2 954529.91 15.405 0.766107 0.203773 297.341
0.00871422
3 954849.8 12.849 0.7277120.0545952 258.471
0.00033166
4 954629.03 13035 0.69114 0.107402 258.048
0.000228815
5 954614.88 33406 0.692682 0.255673 257.828
1.46744e-05
6 954525.69 14111 0.579613 0.143897 256.765
9.24569e-05
7 954539.42 61648 0.581139 0.501345 255.994
1.42362e-05
8 954518.93 22452 0.573652 0.478609 255.465
2.12443e-05
9 954494.92 8540.4 0.556318 0.403754 254.653
2.48944e-05
10 954523.58 20366 0.556265 0.570707 254.104
2.97206e-05
11 954522.07 6142.4 0.554989 0.647881 256.561
1.57288e-06
12 954573.42 6192.9 0.513972 0.716706 253.604
5.32434e-05
13 954575.97 5912.1 0.509457 0.699751 252.612
2.64406e-06
14 954576.23 16534 0.509454 0.674865 253.278
2.64555e-07
15 954579.65 12324 0.509394 0.812237 252.966
3.54362e-06
16 954579.86 7650.3 0.509391 0.80973 252.948
2.18359e-07
17 954579.87 8185.1 0.509391 0.809591 252.947
1.48635e-08
18 954579.88 8696.2 0.509391 0.809411 252.945
1.31087e-08
19 954579.9 9392.5 0.50939 0.80927
Re: PV curve using CPF
Sir,If i want to increase load in continuation power flow by step of 1 MW, What should be the step size of Lamda. My system base case load is 5000 MW. As CPF accuracy depends on step-size. Thanks. From: Jose Luis Marin lt;mari...@gridquant.comgt; Sent: Mon, 10 Aug 2015 18:53:11 To: MATPOWER discussion forum lt;matpowe...@list.cornell.edugt; Subject: Re: PV curve using CPF Shruti is right, the value you obtain for lambda is valid for all the network, since voltage collapse is a global phenomenon (in other words, you';ll see a nose point at the same value of lambda regardless of which bus you choose to plot).nbsp; Remember that lambda represents a fraction along the vector of injections linearly iterpolating [P_base, Q_base]nbsp; tonbsp; [P_target, Q_target].nbsp; The value of Lambda at the nose point is NOT the maximum loading point for that bus; rather, it is the maximum loading value along the path to the particular load/gen profile chosen as a target. Of course, one may wonder about this other problem: for a given profile [P_base, Q_base], what is the target direction [P_target, Q_target] for which one would obtain the shortest value of critical lambda?nbsp; If this is what you';re thinking about, then it is in general a hard problem.nbsp; I suggest these references by Ian Dobson, on the concept of shortest distance to voltage collapse: http://www.ece.wisc.edu/~dobson/PAPERS/publications.html#loading -- Jose L. Marin Gridquant España SL Grupo AIA On Mon, Aug 10, 2015 at 6:23 AM, nilesh patel lt;nk2...@rediffmail.comgt; wrote: Sir,When we run continuation power flow for particular system, we get p-v curve for selected bus. using this p-v curve, we can find Voltage stability Margin (in MW) on that bus by difference of operating point to nose point lamda.nbsp; nbsp; nbsp; nbsp; nbsp; I agree lambda at nose point provides maximum loading value but that is for that bus only for which p-v curve is plotted.nbsp; My question is How to find Voltage Stability Margin for whole Network using P-V curve ? I mean how to find maximum lamda for whole network using nbsp;p-v curve? Thanks. From: Abhyankar, Shrirang G. lt;abhy...@anl.govgt; Sent: Fri, 07 Aug 2015 22:31:31 To: MATPOWER discussion forum lt;matpowe...@list.cornell.edugt; Subject: Re: PV curve using CPF I donⴠquite understand your question, can you please elaborate. The maximum value of loading scaling parameter ᬡmbda⠧ives a measure of how much power can be transferred for a given transfer direction. So, lambda is also a measure of the nose point for the whole network.nbsp; Shri From: nilesh patel lt;nk2...@rediffmail.comgt; Reply-To: MATPOWER discussion forum lt;matpowe...@list.cornell.edugt; Date: Friday, August 7, 2015 at 8:46 AM To: matpower-l lt;matpowe...@list.cornell.edugt;, MATPOWER-L lt;MATPOWER-L@cornell.edugt; Subject: PV curve using CPF Dear Sir, P-V curve solution using continuation power flow gives nose point (maximum loading point) for individual bus. My question is - How to get nose point for whole network (all buses) using PV curve ?nbsp; I want to find network voltage stability margin rather than individual bus margin using CPF. Thanks. Nilesh Patel Get your own FREE website, FREE domain amp; FREE mobile app with Company email. nbsp;Know More gt;
