No real significance. The important thing for maximizing DG output is the difference between the cost of conventional supply and the DG cost. I just mentioned a large positive cost to ensure that there would be a substantive difference.
-- Ray Zimmerman Senior Research Associate B30 Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On Jun 16, 2013, at 3:03 PM, Alexandra Kapetanaki <[email protected]> wrote: > Dear Ray, Dionisis, > > I have included DG in a transmission network as well and I have set zero cost > for the DGs. > My aim is to maximize the output of the DG but I can not understand where is > the benefit of setting a large positive cost on the slack bus gen. > Can you please clarify me the difference of not using the actual cost > cooefficients for all the regular generators? > > Thank you in advance, > kind Regards, > Alexandra Kapetanaki > > 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: 15 June 2013 17:01 > To: MATPOWER discussion forum > Subject: Re: maximise DG > > Your logic sounds correct. You might also just try putting a large positive > cost on the slack bus gen and zero costs on all of the DGs. It should be > equivalent. It could be that there is some tradeoff between maximizing DG and > minimizing losses and the value used for DG cost affects this tradeoff. > > > -- > Ray Zimmerman > Senior Research Associate > B30 Warren Hall, Cornell University, Ithaca, NY 14853 > phone: (607) 255-9645 > > > > > > On Jun 13, 2013, at 7:38 AM, Dionisis Stamatiadis > <[email protected]> wrote: > >> Hi, >> I am using MatPower during my MSc thesis in which I study the behaviour of a >> storage system connected to a distribution network with distributed >> generators (DGs). My objective is to maximise the DG export subject to the >> grid's constraints (voltages, line limits) - objective function: max Pdg. I >> though that putting the costs of the main grid's generator (slack bus) equal >> to zero, and the DGs' costs a negative value I would get the maximum DG >> output. However, it seems that this is not the case since I get a different >> DG export for different negative costs. If I was right, then the DG export >> (maximum achieved subject to system constraints) should be the same for >> every negative cost. >> >> Do you think that my thinking is wrong? What would you suggest me to do in >> order to maximise the DG export. I read section 5.3 but I think that I do >> not have to add more variables and costs, since I can model DG units as >> plain generators. >> >> Thank you in advance, >> Dionisis >> >> > >
