Dear Ray Zimmerman,
Did you see the letter I sent to your mailbox? Maybe it's a supplement for
this problem.
======================================================
After exhaustive tests for parameters setting of Matpower, I found a
problem, maybe a bug. Qmax and Qmin can not be set both as zero, otherwise
the reactive power is unbalanced if the 3.0.0 or 3.1b2 is used.
For an example, the default case14.m. If not both of Qmax and Qmin are zero,
then the PF result shows that the Q of bus1 is -16.55 and Q of the system is
balanced. But if both Qmax and Qmin are zero, Q of bus1 is 0 while Q of the
system is unbalanced.
On the other hand, I found this problem doesn't exit for 3.0b3. Whatever
Qmax and Qmin are set, the PF result always shows that the Q of bus1 is -
16.55 and Q of the system is balanced. So I think maybe it is a bug.
Please explain it, thanks a lot!
=======================================================
Hope the latest version comes soon, :)
--------------
Yours sincerely,
Wu Jun
Unit: State Key Lab. of Power Systems,
Dep. of Electrical Engineering,
Tsinghua University, P.R. China.
2007-04-29
2007/4/30, Ray Zimmerman <[email protected]>:
Hi Jun Wu,
Thanks for pointing this out. You have, indeed, found a bug that was
introduced in 3.0b4 and is present it all subsequent versions. It will be
fixed for the next release.
Specifically, if any generator has QMIN equal to QMAX, the power flow
solution will have Qg incorrectly set to zero for that generator. This does
not affect the OPF.
In response to your question regarding Vg, it should be the desired
voltage set-point for that generator, and in the absence of better
information, 1 p.u. is a reasonable default.
Ray
On Apr 27, 2007, at 11:07 PM, Jun Wu wrote:
By your instruction, the problem is smoothed. Thank you very much!
But I found an interesting thing, the PF result of 3.0b3 is slightly
different from that of 3.0.0 or 3.1b2. The attachment is my test system
and results of different versions. The only difference is the Q of bus 1. I
set the Qmax and Qmin of bus 1 to zero so that I think the Q
calculated should also be zero. But it is not zero by using 3.0b3 while it
is zero by using 3.0.0 or 3.1b2.
By the way, I want to ask another question. If the initial values of Vg
should be 1 or other?
2007/4/27, Ray Zimmerman <[email protected]>:
>
> When upgrading you should completely remove all files from the previous
> version from your Matlab path. Then add all of the files from your new
> version to your Matlab path.
>
>
> If 'isload' is not defined it means you do not have the new version
> installed correctly ... isload.m is one of the files in the new version
> and should be in your path.
> --
> Ray Zimmerman
> Senior Research Associate
> 428-B Phillips Hall, Cornell University, Ithaca, NY 14853
> phone: (607) 255-9645
>
>
> On Apr 27, 2007, at 1:27 AM, Jun Wu wrote:
>
> Dear Ray Zimmerman,
>
> Is the higher version compatible with the lower version well? I found
> some problems. I used 3.0b3 before, which is lack of the new feature
> you've referred. So I copy all files of 3.1b2 to replace them. But the
> same program can not work with the error--Undefined function or method
> 'isload' for input arguments of type 'double'. I don't know how update it
> simply
>
> Yours sincerely,
> Wu Jun
> Unit: State Key Lab. of Power Systems,
> Dep. of Electrical Engineering,
> Tsinghua University, P.R. China.
> Email: [email protected]
> 2007-04-27
>
>
>
> 2007/4/27, Ray Zimmerman <[email protected]>:
> >
> > On Apr 26, 2007, at 11:02 AM, Jun Wu wrote:
> >
> > Thanks for your attention and suggestion. I think reading the manual
> > more will help me. But I never saw it before. Is this the latest feature for
> > version 3.1b2? Does 3.0b3 has this setting?
> >
> >
> >
> > This feature was added in 3.0b4 and was included in the final 3.0.0release (
> > 3.0b4 was a beta version). It is also included in the beta releases
> > for 3.1.
> >
> > By the way, what do below settings mean?
> >
> > 38 - OUT_ALL_LIM, -1 control constraint info output
> > [ -1 - individual flags control what constraint info
> > prints]
> > [ 0 - no constraint info (overrides individual
> > flags) ]
> > [ 1 - binding constraint info (overrides individual
> > flags)]
> > [ 2 - all constraint info (overrides individual
> > flags) ]
> > 39 - OUT_V_LIM, 1 control output of voltage limit
> > info
> > [ 0 - don't
> > print ]
> > [ 1 - print binding constraints
> > only ]
> > [ 2 - print all
> > constraints ]
> > [ (same options for OUT_LINE_LIM, OUT_PG_LIM,
> > OUT_QG_LIM) ]
> > 40 - OUT_LINE_LIM, 1 control output of line limit info
> > 41 - OUT_PG_LIM, 1 control output of gen P limit info
> >
> > 42 - OUT_QG_LIM, 1 control output of gen Q limit
> > info
> >
> >
> >
> > These options control the constraint sections of the output for the
> > OPF solver only.
> >
> >
> > Ray
> >
> > 2007/4/26, Ray Zimmerman <[email protected]>:
> > >
> > > By default, the power flow solver does not take into account the
> > > voltage or reactive power limits. However [1] ...
> > >
> > > For the AC power flow solvers, if the ENFORCE_Q_LIMS option is set
> > > to true (default is false), then if any generator reactive power limit is
> > > violated after running the AC power flow, the corresponding bus is con-
> > > verted to a PQ bus, with the reactive output set to the limit, and the
case
> > > is re-run. The voltage magnitude at the bus will deviate from the
specified
> > > value in order to satisfy the reactive power limit. If the generator at
the
> > > reference bus is reaches a reactive power limit and the bus is converted
to
> > > a PQ bus, the first re- maining PV bus will be used as the slack bus for
the
> > > next iteration. This may result in the real power out- put at this
generator
> > > being slightly off from the specified values.
> > >
> > >
> > > [1] Taken from p. 10 of the User's Manual
(http://www.pserc.cornell.edu/matpower/manual.pdf
> > > ).
> > >
> > > --
> > > Ray Zimmerman
> > > Senior Research Associate
> > > 428-B Phillips Hall, Cornell University, Ithaca, NY 14853
> > > phone: (607) 255-9645
> > >
> > >
> > > On Apr 26, 2007, at 5:23 AM, Wu Jun wrote:
> > >
> > > Hi all,
> > >
> > >
> > > From the case30.m in Matpower, Vmax and Vmin for buses are listed,
> > > also the Qmax and Qmin for generators. I want to know how they work during
> > > the process of calculating the power flow. If one of them are violated,
how
> > > does Matpower treat it? Does Matpower keep the original outputs or change
> > > the calculation condition automatically then put out a result without
> > > breaking any limit?
> > >
> > >
> > > --------------
> > > Yours sincerely,
> > > Wu Jun
> > > Unit: State Key Lab. of Power Systems,
> > > Dep. of Electrical Engineering,
> > > Tsinghua University, P.R. China.
> > > Email: [email protected]
> > > 2007-04-26
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> >
> >
> >
>
>
>
<PF of 3.0b3.txt>
<PF2 of 3.0.0 and 3.1b2.txt>
<testcase30.m>
