Good suggestions, Shri. I've made some changes accordingly that will be in the next version.
-- Ray Zimmerman Senior Research Associate B30 Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On Jun 6, 2013, at 4:41 PM, Shri <[email protected]> wrote: > Perhaps MATPOWER should (i) avoid calling printpf if the PF/OPF does not > converge or (ii) print the 'Converged/Not converged' line after printpf. The > problem is that 'converged/Not converged' line is not glaringly visible. So > even if the OPF does not converge printpf produces output which might fool > some users to think that the system has actually converged. This is certainly > an issue when running large systems because users have to scroll 3-4 screens > up to check whether the PF/OPF has converged when the output is directed to > stdout. > > Shri > On Jun 6, 2013, at 1:38 PM, Ray Zimmerman 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 >> <[email protected]> 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: [email protected] >>> [[email protected]] on behalf of Alexandra >>> Kapetanaki [[email protected]] >>> 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: [email protected] >>> [[email protected]] on behalf of Ray Zimmerman >>> [[email protected]] >>> 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 >>> <[email protected]> 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: [email protected] >>>> [[email protected]] on behalf of Ray Zimmerman >>>> [[email protected]] >>>> 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 >>>> <[email protected]> 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: [email protected] >>>>> [[email protected]] on behalf of Ray Zimmerman >>>>> [[email protected]] >>>>> 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 >>>>> <[email protected]> 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 >>>>> >>>>> >>>> >>>> >>> >>> >> >
