Dear Professor Is that OK send me an orginal form of OPF for the matpower?just OPF
schools of electrical engineering and automation ,Tsinghua University,China.. At 2013-06-07 02:38:53,"Ray Zimmerman" <r...@cornell.edu> wrote: Are you sure the OPF converged? -- Ray Zimmerman Senior Research Associate B30 Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On Jun 5, 2013, at 12:35 PM, Alexandra Kapetanaki <alexandra.kapetan...@manchester.ac.uk> wrote: Dear Ray, I run DC opf for the 24 bus IEEE network and I have negative virtual gen for the representation of the load and for an intact system with 2850 MW load there is 2850 MW dispatchable load. However, in the case I add extra virtual gen to all the 24 buses with zero output (also zero Pmin and Pmax) the dispatchable load is 1036MW instead of 2850MW. Basically, the network is the same eg generation capacity, load, transmission lines's capacity in both cases. The only difference is the extra generators with zero output in the second case. Can you please insight me why the load is not satisfied in the second case? Thank you in advance, Alexandra Alexandra Kapetanaki PhD Student Electrical Energy & Power Systems Group, School of Electrical & Electronic Engineering Ferranti Building (B18), The University of Manchester, M13 9PL, United Kingdom Tel: +44 (0) 161 306 2263; Mobile: +44 (0) 7857 598179 From: bounce-98052467-46384...@list.cornell.edu [bounce-98052467-46384...@list.cornell.edu] on behalf of Alexandra Kapetanaki [alexandra.kapetan...@manchester.ac.uk] Sent: 04 June 2013 15:39 To: MATPOWER discussion forum Subject: RE: transmission losses-DC opf How can I exclude the Q losses in AC opf? Because the formula is applicable in a DC model without the effect of Q. Thank you in advance! Alexandra Kapetanaki PhD Student Electrical Energy & Power Systems Group, School of Electrical & Electronic Engineering Ferranti Building (B18), The University of Manchester, M13 9PL, United Kingdom Tel: +44 (0) 161 306 2263; Mobile: +44 (0) 7857 598179 From: bounce-98052291-46384...@list.cornell.edu [bounce-98052291-46384...@list.cornell.edu] on behalf of Ray Zimmerman [r...@cornell.edu] Sent: 04 June 2013 15:05 To: MATPOWER discussion forum Subject: Re: transmission losses-DC opf I'm not sure, but you could try your formula to estimate the losses for the AC model as well. That would give you an idea of how good your estimate is. -- Ray Zimmerman Senior Research Associate B30 Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On Jun 4, 2013, at 7:10 AM, Alexandra Kapetanaki <alexandra.kapetan...@manchester.ac.uk> wrote: Dear Ray, Thank you for your support! I run DC OPF in the 24 bus IEEE network and my aim is to include a transmission losses model in the system. I followed the procedure you insisted to me and for the losses per line I used the already proved equation Ploss = rij(Pk)^2 which is applicable in a p.u. system. So I divided the Pk of each line by baseMVA(=100) whereas the rij is already in p.u.. However, I compared the losses of the branches for an intact network(24bus) by using AC opf to the corresponding losses by using DC opf and they seem to be different as you can see below: Losses for each branch_DC(real values)= [4,32 6,306 2,4 2,21 2,114 1,173 1,318 5,486 2,31 2,4 5,67 12,4 6,18 3,27 6,791 3,83 14,3655 4,268 5,459 3,761 5,155 5,11 3,94 4,13] Losses for each branch_AC(real values)= [0,0022 0,13 0,864 0,644 1,25 0,156 0,933 0,245 0,059 0,94 1,63 0,756 0,423 0,285 0,35 0,50 0,611 0,537 1,391 0,309 5,80 4,69 6,129 0,030 2,187 2,187 2,692 4,1436 0,230 0,833 2,697 0,191 0,191 0,100 0,100 0,313 0,31 1,829] I would like to let you know that Plosses_AC_opf were obtained by the following command: results_2(N).Plossesbranch_AC(br)=results.branch(br,14)+results.branch(br,16); Why do you think the losses are considerable different between the AC,DC models? In DC the Q is not included so this is one reason of the deviation but is that enough? Thank you in advance, Alexandra Kapetanaki PhD Student Electrical Energy & Power Systems Group, School of Electrical & Electronic Engineering Ferranti Building (B18), The University of Manchester, M13 9PL, United Kingdom Tel: +44 (0) 161 306 2263; Mobile: +44 (0) 7857 598179 From: bounce-96622560-46384...@list.cornell.edu [bounce-96622560-46384...@list.cornell.edu] on behalf of Ray Zimmerman [r...@cornell.edu] Sent: 28 May 2013 17:58 To: MATPOWER discussion forum Subject: Re: transmission losses-piece wise linear approach - Solve a DC OPF with no losses. - Compute the loss for each branch, Ploss = rij(Pk)^2. - Add half of the loss to the load at the buses connected by the branch. - Re-solve the DC OPF. - Recompute the loss for each branch based on the new flow. - Adjust the loads at each end of the branch to reflect the change in losses. - Repeat, until the change from one iteration to the next is smaller than some threshold. -- Ray Zimmerman Senior Research Associate 419A Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On May 28, 2013, at 12:25 PM, Alexandra Kapetanaki <alexandra.kapetan...@manchester.ac.uk> wrote: Dear Ray, Thank you for your help! Can you please explain me more what do you mean with the "adjusting the set of dummy loads used to represent losses based on flows in the previous iteration". For example, I want to represent the losses as dummy loads according to the following figure: <losses.png> and express the losses by using the quadratic equation : Ploss=rij(Pk)^2 . How can I practically implement that within "few iterations", as you recommend? Thank you once again for your support, Alexandra Kapetanaki PhD Student Electrical Energy & Power Systems Group, School of Electrical & Electronic Engineering Ferranti Building (B18), The University of Manchester, M13 9PL, United Kingdom Tel: +44 (0) 161 306 2263; Mobile: +44 (0) 7857 598179 From: bounce-96622396-46384...@list.cornell.edu [bounce-96622396-46384...@list.cornell.edu] on behalf of Ray Zimmerman [r...@cornell.edu] Sent: 28 May 2013 16:55 To: MATPOWER discussion forum Subject: Re: transmission losses-piece wise linear approach Dear Alexandra, Since the network equations in MATPOWER's DC OPF assume no losses, it seems you would have to introduce the losses as dummy (dispatchable) loads at the downstream end of each branch. You would have to add an additional set of constraints for each of these dummy loads constraining the consumption lie above the piecewise linear constraints you propose. These constraints could be added using the mechanism for user-defined constraints described in section 5.3.2 and chapter 6 of the User's Manual. Another approach to using MATPOWER to solve a "DC OPF with losses" is to simply run the DC OPF iteratively, each time adjusting the set of dummy loads used to represent losses based on flows in the previous iteration. I'm guessing it wouldn't require more than a few iterations to converge to a pretty good solution. This approach is a bit brute-force, but may be simpler to implement and allows you to use whatever function you like (e.g. a quadratic) to compute the losses. Just another idea. -- Ray Zimmerman Senior Research Associate 419A Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On May 27, 2013, at 3:16 PM, Alexandra Kapetanaki <alexandra.kapetan...@manchester.ac.uk> wrote: Dear Dr Ray, As the AC power flow requires high computation time for the losses to be calculated, a DC opf can be used in conjuction with a linear model for transmission losses. My aim is to adjust the piece wise linear approach of Matpower in order to accommodate the losses of a transmission line. More particularly, the losses can be expressed through the following equation: Ploss=rij(Pk)^2 [where rij the resistance of the line and Pk the power flow in the transmission line]. However, the above equation is a quadratic function but can be expressed with a piecewise linear model. The figure below shows a linear model consists of N line pieces <piecewiselinear.png> the equation of the nth line piece is: <bbbbbbbbbbbbbbb.png> -How can I modify the piece wise linear approach of Matpower with the view to include the losses model? Thank you in advance, Alexandra Kapetanaki PhD Student Electrical Energy & Power Systems Group, School of Electrical & Electronic Engineering Ferranti Building (B18), The University of Manchester, M13 9PL, United Kingdom Tel: +44 (0) 161 306 2263; Mobile: +44 (0) 7857 598179
