If you construct a user cost function (section 5.3.1 of the manual) with an N matrix that gives you an r vector equal to the flows, you should be able to put appropriate costs on them. If that approach doesn't work, I have another more complicated idea that involves splitting each branch so it has two dummy nodes in the middle, then add some dummy generators and some constraints at the dummy nodes.
-- Ray Zimmerman Senior Research Associate 211 Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On May 13, 2011, at 1:23 PM, Santiago Chamba wrote: > Thank Professor Zimmerman for your explanation. Now I have very clear my bug. > > I have a new question. I want to modify the objective function, because I > need to introduce transmission auction in the day-ahead market (Offer and > bids). > For my case, I must to introduce the transmission offer and the transmission > cost, i.e., my objective function is: > > Minimize : Price(transaction)*P(transaction) + Cost(transmission)*fk) > Subjet to > Nodal balance equations: [Pg-Pd]=[B][Teta]=[=[IT(transaction]*P(transaction) > Transmission limits: (-fk)max< fk <(f k)max > > Where: > Price(transaction): offer price ($/MWh). > If transaction is an extraction request (demand), the price (positive) will > be the maximum price that the bidder is willing to pay for the purchase of > energy. > If transaction is an injection offer, the price (negative) will be the > minimum price that the bidder is willing to receive for the sale of energy. > If transaction is a request for transmission services between two nodes, the > price (positive) will be the maximum price that the bidder is willing to pay > for the requested transmission services. > > The algorithm determines the optimal dispatch of the opportunity bids and > offers and the optimal allocation of transmission services, and produces > buying/selling opportunity prices (nodal prices) and transmission services > prices (differences of nodal prices). > > Then, I need to introduce transmission limits in two directions and modify > the objective functions to consider the transmission cost and the services > transmission offer. > > I do not know, If the characteristics above mentioned are possible introduce > in Matpower?, Otherwise ¿Could I use some Matpower’s files for Objective? > > Best regards > > De: [email protected] > [mailto:[email protected]] En nombre de Ray Zimmerman > Enviado el: jueves, 12 de mayo de 2011 16:13 > Para: MATPOWER discussion forum > Asunto: Re: Mistake_Auctions > > I am assuming you are running this with offers/bids defined by what is in > gencost. In the first case, the incremental cost of generation between 50 MW > and 100 MW of output is $15/MWh. Likewise the incremental benefit for the > load between 60 MW and 90 MW is also $15/MWh. For the (lossless) DC OPF > problem, this means that the objective function value does not change as the > dispatch changes between 60 and 90 MW ... i.e. for the exact bids and offers > you are using there is no unique minimizing solution to the DC problem. For > the AC problem, the losses create a small price difference between the buses, > eliminating solutions with greater than 60 MW of demand, so there is a unique > solution. > > In the case with the line constraint at 50 MW, once again, you are creating > an anomaly by setting the constraint value to fall *exactly* on the corner > point of the generator's cost function. If you set it to something slightly > less than 50, then the prices will be pretty close to the expected $10 and > $18. If you set it slightly greater than 50, then the prices will be $15 and > $18. Strictly speaking, the node 1 price for a line capacity of exactly 50 MW > is not uniquely defined. It can be anything between $10 and $15. > > Hope this helps, > > -- > Ray Zimmerman > Senior Research Associate > 211 Warren Hall, Cornell University, Ithaca, NY 14853 > phone: (607) 255-9645 > > > > > On May 12, 2011, at 12:58 PM, Santiago Chamba wrote: > > > Dear Professor Zimmerman, > > I think that there is a probable mistake in the auction method (smartmarket), > specifically in DC OPF. I run a smartmarket and OPF (DC and AC) without fixed > load, i.e., the two nodes system only has generators offers and demand bids > (inelastic). > > When, I run AC OPF the results are correct, but with DC OPF the results may > be wrong, because the inyections and extractions electricity are very > different to the AC responses: > > Node DC OPF DC OPF > Pot Lambda Pot Lambda > MW $/MW MW $/MW > 1 70.8298 15 60.0394 15.00 > 2 -70.8298 15 -60.0067 15.016 > > I think the correct responses for DC OPF is 60 MW in the two nodes. Why are > the AC and DC results so different? > > When, the capacity line decreases to 50 MW, the inyections and extractions > electricity are correct, but the prices changes: > > Node DC OPF DC OPF > Pot Lambda Pot Lambda > MW $/MW MW $/MW > 1 50 11.32 49.99 10 > 2 -50 18.00 -49.97 18 > > I think the correct responses for DC OPF is 10 and 18 ($/MW). Why are the > prices (AC and DC) in the node 1 so different? > > Please, explain me What is my mistake? or Where can I modify the mistake?. > Because I need the model for my investigation. > > Thank > > > > <subasta.m> >
