That's very interesting. I run the case14 as below and get convergence in 1
iteration. However, the convergence aside, I still get different results when I
run a PF calculation of my model using the results of a previous OPF
calculation - these results are different by 100's of MVAR's. To me this
implies that the solution given by the opf is not attainable using pf, ie that
it is incorrect, or that the opf voltage results are not matched to the opf
power flow results. Could this also be a bug?
Regards,
Dominic
mpc=loadcase('case14.m');
resultsOPF=runopf(mpc);
resultsPF=runpf(resultsOPF);
MATPOWER Version 5.0, 17-Dec-2014 -- AC Optimal Power Flow
PDIPMOPF Version 4.1, Build 18, 11-Nov-2011
Copyright (c) 2007-2011 by Power System Engineering Research Center (PSERC)
Converged in 0.03 seconds
Objective Function Value = 8081.53 $/hr
================================================================================
| System Summary |
================================================================================
How many? How much? P (MW) Q (MVAr)
--------------------- ------------------- ------------- -----------------
Buses 14 Total Gen Capacity 772.4 -52.0 to 148.0
Generators 5 On-line Capacity 772.4 -52.0 to 148.0
Committed Gens 5 Generation (actual) 268.3 67.6
Loads 11 Load 259.0 73.5
Fixed 11 Fixed 259.0 73.5
Dispatchable 0 Dispatchable -0.0 of -0.0 -0.0
Shunts 1 Shunt (inj) -0.0 20.7
Branches 20 Losses (I^2 * Z) 9.29 39.16
Transformers 3 Branch Charging (inj) - 24.3
Inter-ties 0 Total Inter-tie Flow 0.0 0.0
Areas 1
Minimum Maximum
------------------------- --------------------------------
Voltage Magnitude 1.014 p.u. @ bus 4 1.060 p.u. @ bus 1
Voltage Angle -14.27 deg @ bus 14 0.00 deg @ bus 1
P Losses (I^2*R) - 2.90 MW @ line 1-2
Q Losses (I^2*X) - 8.86 MVAr @ line 1-2
Lambda P 36.72 $/MWh @ bus 1 41.20 $/MWh @ bus 14
Lambda Q -0.09 $/MWh @ bus 1 0.57 $/MWh @ bus 14
================================================================================
| Bus Data |
================================================================================
Bus Voltage Generation Load Lambda($/MVA-hr)
# Mag(pu) Ang(deg) P (MW) Q (MVAr) P (MW) Q (MVAr) P Q
----- ------- -------- -------- -------- -------- -------- ------- -------
1 1.060 0.000* 194.33 0.00 - - 36.724 -0.094
2 1.041 -4.022 36.72 23.69 21.70 12.70 38.360 -
3 1.016 -9.926 28.74 24.13 94.20 19.00 40.575 -
4 1.014 -8.665 - - 47.80 -3.90 40.190 0.120
5 1.016 -7.428 - - 7.60 1.60 39.661 0.208
6 1.060 -12.689 0.00 11.55 11.20 7.50 39.734 -
7 1.046 -11.188 - - - - 40.172 0.120
8 1.060 -10.415 8.49 8.27 - - 40.170 -
9 1.044 -12.997 - - 29.50 16.60 40.166 0.196
10 1.039 -13.233 - - 9.00 5.80 40.318 0.309
11 1.046 -13.091 - - 3.50 1.80 40.155 0.228
12 1.045 -13.533 - - 6.10 1.60 40.379 0.212
13 1.040 -13.583 - - 13.50 5.80 40.575 0.353
14 1.024 -14.274 - - 14.90 5.00 41.197 0.571
-------- -------- -------- --------
Total: 268.29 67.63 259.00 73.50
================================================================================
| Branch Data |
================================================================================
Brnch From To From Bus Injection To Bus Injection Loss (I^2 * Z)
# Bus Bus P (MW) Q (MVAr) P (MW) Q (MVAr) P (MW) Q (MVAr)
----- ----- ----- -------- -------- -------- -------- -------- --------
1 1 2 129.67 -6.36 -126.77 9.40 2.902 8.86
2 1 5 64.66 6.37 -62.61 -3.21 2.051 8.47
3 2 3 55.59 0.47 -54.25 0.56 1.344 5.66
4 2 4 48.92 -0.48 -47.63 0.79 1.285 3.90
5 2 5 37.28 1.59 -36.54 -3.00 0.737 2.25
6 3 4 -11.21 4.57 11.31 -5.63 0.099 0.25
7 4 5 -49.17 11.58 49.50 -10.53 0.331 1.04
8 4 7 22.85 -3.99 -22.85 5.04 0.000 1.05
9 4 9 14.84 1.17 -14.84 -0.04 0.000 1.12
10 5 6 42.06 15.14 -42.06 -10.90 0.000 4.23
11 6 11 6.09 4.56 -6.04 -4.46 0.049 0.10
12 6 12 7.65 2.66 -7.58 -2.51 0.072 0.15
13 6 13 17.12 7.73 -16.91 -7.32 0.208 0.41
14 7 8 -8.49 -8.05 8.49 8.27 0.000 0.22
15 7 9 31.34 3.01 -31.34 -2.02 0.000 1.00
16 9 10 6.49 3.20 -6.47 -3.16 0.015 0.04
17 9 14 10.20 2.95 -10.06 -2.67 0.131 0.28
18 10 11 -2.53 -2.64 2.54 2.66 0.010 0.02
19 12 13 1.48 0.91 -1.47 -0.91 0.006 0.01
20 13 14 4.88 2.42 -4.84 -2.33 0.047 0.10
-------- --------
Total: 9.287 39.16
================================================================================
| Voltage Constraints |
================================================================================
Bus # Vmin mu Vmin |V| Vmax Vmax mu
----- -------- ----- ----- ----- --------
1 - 0.940 1.060 1.060 583.780
6 - 0.940 1.060 1.060 55.184
8 - 0.940 1.060 1.060 71.069
================================================================================
| Generation Constraints |
================================================================================
Gen Bus Active Power Limits
# # Pmin mu Pmin Pg Pmax Pmax mu
---- ----- ------- -------- -------- -------- -------
4 6 0.266 0.00 0.00 100.00 -
Gen Bus Reactive Power Limits
# # Qmin mu Qmin Qg Qmax Qmax mu
--- --- ------- -------- -------- -------- -------
1 1 0.094 0.00 0.00 10.00 -
MATPOWER Version 5.0, 17-Dec-2014 -- AC Power Flow (Newton)
Newton's method power flow converged in 1 iterations.
Converged in 0.00 seconds
Objective Function Value = 8081.53 $/hr
================================================================================
| System Summary |
================================================================================
How many? How much? P (MW) Q (MVAr)
--------------------- ------------------- ------------- -----------------
Buses 14 Total Gen Capacity 772.4 -52.0 to 148.0
Generators 5 On-line Capacity 772.4 -52.0 to 148.0
Committed Gens 5 Generation (actual) 268.3 67.6
Loads 11 Load 259.0 73.5
Fixed 11 Fixed 259.0 73.5
Dispatchable 0 Dispatchable -0.0 of -0.0 -0.0
Shunts 1 Shunt (inj) -0.0 20.7
Branches 20 Losses (I^2 * Z) 9.29 39.16
Transformers 3 Branch Charging (inj) - 24.3
Inter-ties 0 Total Inter-tie Flow 0.0 0.0
Areas 1
Minimum Maximum
------------------------- --------------------------------
Voltage Magnitude 1.014 p.u. @ bus 4 1.060 p.u. @ bus 1
Voltage Angle -14.27 deg @ bus 14 0.00 deg @ bus 1
P Losses (I^2*R) - 2.90 MW @ line 1-2
Q Losses (I^2*X) - 8.86 MVAr @ line 1-2
Lambda P 36.72 $/MWh @ bus 1 41.20 $/MWh @ bus 14
Lambda Q -0.09 $/MWh @ bus 1 0.57 $/MWh @ bus 14
================================================================================
| Bus Data |
================================================================================
Bus Voltage Generation Load Lambda($/MVA-hr)
# Mag(pu) Ang(deg) P (MW) Q (MVAr) P (MW) Q (MVAr) P Q
----- ------- -------- -------- -------- -------- -------- ------- -------
1 1.060 0.000* 194.33 0.00 - - 36.724 -0.094
2 1.041 -4.022 36.72 23.69 21.70 12.70 38.360 -
3 1.016 -9.926 28.74 24.13 94.20 19.00 40.575 -
4 1.014 -8.665 - - 47.80 -3.90 40.190 0.120
5 1.016 -7.428 - - 7.60 1.60 39.661 0.208
6 1.060 -12.689 0.00 11.55 11.20 7.50 39.734 -
7 1.046 -11.188 - - - - 40.172 0.120
8 1.060 -10.415 8.49 8.27 - - 40.170 -
9 1.044 -12.997 - - 29.50 16.60 40.166 0.196
10 1.039 -13.233 - - 9.00 5.80 40.318 0.309
11 1.046 -13.091 - - 3.50 1.80 40.155 0.228
12 1.045 -13.533 - - 6.10 1.60 40.379 0.212
13 1.040 -13.583 - - 13.50 5.80 40.575 0.353
14 1.024 -14.274 - - 14.90 5.00 41.197 0.571
-------- -------- -------- --------
Total: 268.29 67.63 259.00 73.50
================================================================================
| Branch Data |
================================================================================
Brnch From To From Bus Injection To Bus Injection Loss (I^2 * Z)
# Bus Bus P (MW) Q (MVAr) P (MW) Q (MVAr) P (MW) Q (MVAr)
----- ----- ----- -------- -------- -------- -------- -------- --------
1 1 2 129.67 -6.36 -126.77 9.40 2.902 8.86
2 1 5 64.66 6.37 -62.61 -3.21 2.051 8.47
3 2 3 55.59 0.47 -54.25 0.56 1.344 5.66
4 2 4 48.92 -0.48 -47.63 0.79 1.285 3.90
5 2 5 37.28 1.59 -36.54 -3.00 0.737 2.25
6 3 4 -11.21 4.57 11.31 -5.63 0.099 0.25
7 4 5 -49.17 11.58 49.50 -10.53 0.331 1.04
8 4 7 22.85 -3.99 -22.85 5.04 0.000 1.05
9 4 9 14.84 1.17 -14.84 -0.04 0.000 1.12
10 5 6 42.06 15.14 -42.06 -10.90 0.000 4.23
11 6 11 6.09 4.56 -6.04 -4.46 0.049 0.10
12 6 12 7.65 2.66 -7.58 -2.51 0.072 0.15
13 6 13 17.12 7.73 -16.91 -7.32 0.208 0.41
14 7 8 -8.49 -8.05 8.49 8.27 0.000 0.22
15 7 9 31.34 3.01 -31.34 -2.02 0.000 1.00
16 9 10 6.49 3.20 -6.47 -3.16 0.015 0.04
17 9 14 10.20 2.95 -10.06 -2.67 0.131 0.28
18 10 11 -2.53 -2.64 2.54 2.66 0.010 0.02
19 12 13 1.48 0.91 -1.47 -0.91 0.006 0.01
20 13 14 4.88 2.42 -4.84 -2.33 0.047 0.10
-------- --------
Total: 9.287 39.16
================================================================================
| Voltage Constraints |
================================================================================
Bus # Vmin mu Vmin |V| Vmax Vmax mu
----- -------- ----- ----- ----- --------
1 - 0.940 1.060 1.060 583.780
6 - 0.940 1.060 1.060 55.184
8 - 0.940 1.060 1.060 71.069
================================================================================
| Generation Constraints |
================================================================================
Gen Bus Active Power Limits
# # Pmin mu Pmin Pg Pmax Pmax mu
---- ----- ------- -------- -------- -------- -------
4 6 0.266 0.00 0.00 100.00 -
Gen Bus Reactive Power Limits
# # Qmin mu Qmin Qg Qmax Qmax mu
--- --- ------- -------- -------- -------- -------
1 1 0.094 0.00 0.00 10.00 -
>> compare_case(resultsOPF, resultsPF)
---------------- -------------- -------------- -------------- -----
matrix / col case 1 case 2 difference row
---------------- -------------- -------------- -------------- -----
bus
VM 1.03914 1.03914 7.68601e-11 10
VA -14.2741 -14.2741 2.45214e-07 14 *
gen
PG 194.33 194.33 5.37223e-08 1
QG 11.5455 11.5455 1.64362e-07 4 *
branch
PF 42.0553 42.0553 9.84285e-08 10 *
QF -8.05255 -8.05255 3.0924e-08 14
PT -42.0553 -42.0553 9.84285e-08 10
QT 8.27299 8.27299 2.97751e-08 14
>>
Von: [email protected]
[mailto:[email protected]] Im Auftrag von Abhyankar,
Shrirang G.
Gesendet: Mittwoch, 28. Januar 2015 20:55
An: MATPOWER discussion forum
Betreff: Re: AW: Solved case does not converge in zero iterations
I think the runopf routine should update generator set point voltages in the
mpc struct once a solution is found. It is clearly a bug if that's not the case.
I did a quick check on case14 and found that the power flow converges in 0
iterations given an initial guess from the OPF solution. With case118, the
power flow takes 1 iteration. Note that power flow uses a default convergence
tolerance of 1e-8. For case14, the mismatch norm at iteration 0 is ~ 1-e10,
while for case118 it is ~ 1e-7. Hence, the power flow converges in 0 iterations
for case14 and in 1 iteration for case118. Regardless, you should expect almost
same solutions (accuracy ~ tolerance settings) for OPF and PF.
Shri
From: Carlos E Murillo-Sanchez
<[email protected]<mailto:[email protected]>>
Reply-To: MATPOWER discussion forum
<[email protected]<mailto:[email protected]>>
Date: Wed, 28 Jan 2015 14:39:48 -0500
To: MATPOWER discussion forum
<[email protected]<mailto:[email protected]>>
Subject: Re: AW: Solved case does not converge in zero iterations
Dear Dominic:
The PF solver takes the generator voltage setpoint from the gen(:, VG), thus
changing the voltage values set by the OPF at generator buses. Try
resultsOPF=runopf(mpc) %calculate opf
mpc.gen=resultsOPF.gen %update mpc with optimal P,V
and angle values
mpc.bus=resultsOPF.bus
mpc.gen(:, VG) = mpc.bus(mpc.gen(:, GEN_BUS), VM);
resultsPF=runpf(mpc)
Regards,
carlos.
Hewes, Dominic wrote:
Hi Uriel,
Thanks for your quick response. I understand that the opf varies the PV bus
voltages (and other variables) in order to achieve an optimal solution.
However, if I take the results of the opf (i.e the optimal generator P, V and
bus V,Angle etc) and use these to run a pf (which as you say fixes these
variables and does not allow them to change) then why should I get different
results in comparison to the opf results?
Maybe my method description could be clearer. If I first run an opf, and then
update my original mpc struct with the voltages, angles and powers from the opf
results, and then run a pf, surely I should get the same results as were output
by the opf? ie:
resultsOPF=runopf(mpc) %calculate opf
mpc.gen=resultsOPF.gen %update mpc with optimal P,V
and angle values
mpc.bus=resultsOPF.bus
resultsPF=runpf(mpc) %run pf to calculate
power flows given by the optimal P,V and angle values
Does this make any sense?
Again, thanks for the response.
Regards,
Dominic
Von:
[email protected]<mailto:[email protected]>
[mailto:[email protected]] Im Auftrag von Uriel
Fernando Sandoval
Gesendet: Mittwoch, 28. Januar 2015 20:02
An: MATPOWER discussion forum
Betreff: Re: Solved case does not converge in zero iterations
Hello Dominic,
Probably you are confusing what is the objective of each routine:
On one hand opf tries to minimize the production cost subject to voltage
constraints : Vmin<= V <= Vmax (for all buses, even PV buses) and other network
constraints, therefore, opf does not fix the terminal voltage of the generators.
On the other hand pf solves and obtain an equilibrium point that satisfy power
balance equations, but, in this case pf fixes the terminal voltage the
generators (PV buses) Vk == Vref.
IMHO that is the reason why your are experiencing those differences.
Best,
Uriel
El 28/01/2015, a las 10:42, Hewes, Dominic
<[email protected]<mailto:[email protected]>> escribió:
Dear Matpower Community,
I am observing a strange problem whereby the results from a successful
'runopf()' do not seem to present a solved power flow case. I want to verify
the power flow solution from an OPF by running a PF with the OPF results as the
mpc struct. Firstly, the 'runpf()' converges in 1 iteration, whereas i would
expect a solved case to converge in 0 iterations- am i mistaken here? Secondly,
when i use the 'compare_case()' command to compare the OPF results with the
resulting PF results, I see that there are large differences between the
solutions. My code is as follows:
resultsOPF=runopf(mpc123);
resultsPF=runpf(resultsOPF);
compare_case(resultsOPF, resultsPF)
The comparison shows a maximum reactive power difference of 494 MVAR between
the generator results:
gen
PG 5.00578e-10 9.67145e-09 9.17088e-09 614
QG 7.99959e-11 494.118 494.118 218 *
The OPF command converges successfully with no error warnings, and so I assumed
that running the results struct through a PF command should give the same power
flow solution. Am i mistaken here? If my thinking is correct, this would
indicate that the optimiser has provided results that do not represent a
feasible power flow solution - is this potentially a bug? I have tested the
same method on the 'case14.m' file and observe that this also requires 1
iteration to converge and gives very small differences (~2e-7) between the OPF
and PF results.
I am using the latest matpower release (5.0), the TSPOPF 5.0 solver and a
windows 7 machine (see output of mpver at end of email). I have tried with
other solvers and observe the same problem. I am working with a large model
(>5000 bus) that i have attached below. Could the size of my model be the cause
of this problem?
Presently I am not sure whether I am making a simple mistake or if there is a
bug in the solver that is causing the output of inaccurate results.
Has anyone experienced similar problems? I would very much appreciate any
advice on the cause of the problem.
Kind Regards,
Dominic
mpver
MATPOWER Version 5.0 17-Dec-2014
MATLAB Version 8.4 08-Sep-2014 Release: (R2014b)
Optimization Toolbox Version 7.1 08-Sep-2014 Release: (R2014b)
MIPS Version 1.1 17-Dec-2014
SDP_PF -- not installed --
YALMIP -- not installed --
BPMPD_MEX -- not installed --
CPLEX Version 12.6.0.0 PCWIN64
Gurobi -- not installed --
GLPK -- not installed --
IPOPT -- not installed --
KNITRO -- not installed --
MINOPF -- not installed --
MOSEK -- not installed --
PDIPMOPF Version 5.0 17-Dec-2014 PCWIN64
SCPDIPMOPF Version 5.0 17-Dec-2014 PCWIN64
SDPT3 -- not installed --
SeDuMi -- not installed --
TRALMOPF Version 5.0 17-Dec-2014 PCWIN64
Architecture: PCWIN64
<mpc123.mat>
