Dear professor, Thanks for your reply. So in the 14 bus case, if I change 14 bus branch's RATE_A to a reasonable value, for example, around its branch injection, to create a binding, the saturation percentage will be meaningful in a 14 case. Am I right?
Thanks in advance. ________________________________ From: Ray Zimmerman <[email protected]> To: MATPOWER discussion forum <[email protected]> Sent: Friday, April 5, 2013 3:23 PM Subject: Re: saturation of the branch RATE_A, RATE_B and RATE_C are the parameters that define the long-term, short-term and emergency MVA ratings of the lines. MATPOWER uses RATE_A to define the line limit for the sake of OPF calculations. Some data files, such as the 14-bus case did not include any real line flow limit data and the CDF to MATPOWER conversion program used to generate case14.m from the CDF file inserted 9900 for lines with no limits. So in such a case talking about saturation as a percentage of the (arbitrarily invented) limit is meaningless. With an OPF solution, unless a line constraint is binding (i.e. the flow is equal to the limit) it has no impact on the solution, including the nodal prices. -- Ray Zimmerman Senior Research Associate 419A Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On Apr 5, 2013, at 3:05 PM, Yahook K <[email protected]> wrote: Dear professor, >I am not familiar with the conceptino of Rate_A Rate_B Rate_C . Can you give >me a clue where it is explained? > > >When I check the mpc.branch(:,RATE_A) in a 14 bus case, I found its value is >all 9900 MVA. In your last email, you said the line limit (RATE_A) on lines >that are at 100% of their capacity. Do you mean that this capacity (9900 MVA) >is so high that there is no congestion cost in the lamda P? > > > >Thank you in advance. > > > > >________________________________ > From: Ray Zimmerman <[email protected]> >To: MATPOWER discussion forum <[email protected]> >Sent: Thursday, April 4, 2013 10:46 AM >Subject: Re: saturation of the branch > > >There are an infinite number of ways to modify the inputs to an OPF to achieve >a desired change in the flow of power on a given branch. Each one will result >in different set of prices. I'm afraid your problem is not well-defined. > > >Maybe you really want to look at changing the line limit (RATE_A) on lines >that are at 100% of their capacity? > > >-- >Ray Zimmerman >Senior Research Associate >419A Warren Hall, Cornell University, Ithaca, NY 14853 >phone: (607) 255-9645 > > > > >On Apr 3, 2013, at 6:00 PM, Yahook K <[email protected]> wrote: > >Respected Sir, >> >>Thank you very much for your reply. >> >>My 3rd question is : I want to change the saturation percentage of a certain branch A (for example, from the original 50% to 120% or 98%)to see its influence to the LMP price of all the buses. That is, I want to see the transmission line congestion impacts on the LMP price. >> >>How to achieve that? >> >>In my opinion, to achieve that, I want to change the power demand quantity(PD) of a certain bus B, so that the saturation percentage of branch A will change to 120% or 98%. Then, I runopf to check the Lamda P price and compared the Lamda P price with the previous price when the saturation percentage of branch A is 50%. Am I right? >> >>Please shed light on me. Thanks. >> >> >> >> >> >> >>________________________________ >> From: Ray Zimmerman <[email protected]> >>To: MATPOWER discussion forum <[email protected]> >>Sent: Wednesday, April 3, 2013 9:39 AM >>Subject: Re: saturation of the branch >> >> >>Table B-3 in the User's Manual (or help caseformat) describes the fields of >>the branch matrix. RATE_A is the limit used by runopf(). Please note that for >>an AC power flow model it is an MVA limit, and for DC power flow it is a MW >>limit. So that saturation percentage as you call it would be … >> >> >>define_constants; >>if <AC power flow> >> saturation = sqrt(results.branch(:, PF).^2 + results.branch(:, PT).^2) ./ >>results.branch(:, RATE_A); >>else >> saturation = abs(results.branch(:, PF)) ./ results.branch(:, RATE_A); >>end >> >> >> >>I'm afraid I don't understand your 3rd question. >> >> >>-- >>Ray Zimmerman >>Senior Research Associate >>419A Warren Hall, Cornell University, Ithaca, NY 14853 >>phone: (607) 255-9645 >> >> >> >> >>On Apr 3, 2013, at 1:18 AM, Yahook K <[email protected]> wrote: >> >>Respected Sir, >>> >>> >>>From mpc.branch, I can get the From bus injection and the To bus injection >>>of each branch. But how can I calculate the saturation percentage of the >>>branch? For example, the branch has a limit of 15 MW, and there are 5 MW >>>flowing in this branch. I think to calculate the saturation percentage we do >>>5/15=1/3 >>> >>> >>>Another question is where to find the limit for each branch? >>> >>> >>>The third question would be if I wanna set the branch saturation percentage >>>to 50%, 90% 120%, break. How can I do it? Can you give me some guidance? >>> >>> >>>Please shed light on me. Thank you. >>> >>> >>> >>> >> >> >> > > >
