-- Ray Zimmerman Senior Research Associate 428-B Phillips Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645
On Apr 30, 2007, at 11:05 AM, Jun Wu wrote: 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. 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 3.0.0 release (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.
-- 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. 2007-04-26
<PF of 3.0b3.txt> <PF2 of 3.0.0 and 3.1b2.txt> <testcase30.m>
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pfsoln.m