power flow problem

[Mohamed Shaheen]

Dear Sir,

Regarding the case57, the voltage of bus 31 is 0.936 p.u which is less than
the min. limit of bus voltage (0.94). Every time I run 'runpf', the voltage
value is 0.936 and it doesn't change although it is a PQ bus.
I need your help, please.

Regards,
Mohamed Shaheen.

Msc. student at Ain Shams University in Egypt
Teaching Assistant in Future University in Egypt
ᐧ

Re: Multi-period AC runpf( load flow)

[Ray Zimmerman]

That’s exactly how I would handle it.

   Ray


> On Feb 7, 2019, at 11:38 AM, Ahmad Sadiq Abubakar 
>  wrote:
> 
> Hi,
> How can I run a load flow using runpf with 24-h varying loads (P, Q)?
> 
> The only way I have thought of is to have a for loop.
> Your comments, suggestions and guides will be appreciated.
> Sadiq A. A

Re: Question about extended OPF optimality

[Ray Zimmerman]

The method used by MIPS is a local method, based on solving for local 
optimality conditions. So, the answer is … no, there is no guarantee that it is 
globally optimal. With the standard active power cost, in my experience, the 
local solutions are often globally optimal or extremely close, with local 
optima differing almost exclusively in voltage/reactive dispatch. However, I do 
not really have experience with the objective you describe, so I don’t have a 
good feel for the behavior of that problem.

Ray


> On Feb 7, 2019, at 8:41 AM, Mariusz Drabecki  wrote:
> 
> Dear All,
>  
> I would like to ask you if OPF solved by MIPS solver is proven to be globally 
> optimal? 
>  
> I am especially interested by the case when we substitute the standard  
> active cost by linear costs on reactive power generation and on voltage 
> levels.
>  
> I was trying to prove it myself yet got a feeling that we might have many 
> local minima and the result might not necessarily be global optimal. What 
> would be your opinion on that?
>  
> Best,
> Mariusz
> 
>  
> 
>  Wolny od wirusów. www.avg.com 
> 

Re: power flow problem

[Ray Zimmerman]

The power flow problem solved by runpf does not take into account voltage 
limits. If you need to enforce limits, you can use an appropriately constrained 
OPF.

In this case, it just so happens that the initial voltage specified for bus 31 
in the case57.m file happens to be the voltage at the power flow solution.

Ray


> On Feb 8, 2019, at 2:54 PM, Mohamed Shaheen  
> wrote:
> 
> Dear Sir,
> 
> Regarding the case57, the voltage of bus 31 is 0.936 p.u which is less than 
> the min. limit of bus voltage (0.94). Every time I run 'runpf', the voltage 
> value is 0.936 and it doesn't change although it is a PQ bus.
> I need your help, please.   
> 
> Regards,
> Mohamed Shaheen.
> 
> Msc. student at Ain Shams University in Egypt
> Teaching Assistant in Future University in Egypt
> ᐧ

Re: power flow problem

[Mirish Thakur]

Didn't  understand your question. If I'm correct then you're performing
simple power flow on your case. In this case solver doesn't consider any
restriction/ constraints on problem, means, No branch limits No voltage
limits are applicable . If you want to impose any voltage limits on system
then you have to run optimal power flow. So, instead runpf(case57) , you've
to perform runopf(case57) then you'll see desired output. Please go through
this link might clear your doubt:
*https://www.mail-archive.com/matpower-l@cornell.edu/msg02926.html
*
Thank you.

On Fri, Feb 8, 2019 at 9:54 PM Mohamed Shaheen <
mohamed.shaheen9...@gmail.com> wrote:

> Dear Sir,
>
> Regarding the case57, the voltage of bus 31 is 0.936 p.u which is less
> than the min. limit of bus voltage (0.94). Every time I run 'runpf', the
> voltage value is 0.936 and it doesn't change although it is a PQ bus.
> I need your help, please.
>
> Regards,
> Mohamed Shaheen.
>
> Msc. student at Ain Shams University in Egypt
> Teaching Assistant in Future University in Egypt
> ᐧ
>