It works for me if I explicitly set bus 2 to be type REF. MATPOWER does not automatically detect islands and convert the first PV bus to REF.
-- Ray Zimmerman Senior Research Associate 419A Warren Hall, Cornell University, Ithaca, NY 14853 phone: (607) 255-9645 On Apr 17, 2013, at 12:46 PM, Tao HUANG <[email protected]> wrote: > I quickly tried on a very simple 3 buses system (pls check the attached > figure) modified based on the t_case9_dcline system to test the islands. > Firstly I set the status of line 1-2 equal to 1, then both PF and OPF works > fine. In this case, with the replacement of dummy generators for the DC > lines, the whole system is still connected. > Then, I set the status of line 1-2 equal to 0, then both PF and OPF do not > converge. In this case, by using the dummy generators to model the DC line, > the network was split into to 2 islands. By the way, I put a generator at bus > 2 so each island should have a reference bus (suppose Matpower would use the > first PV bus as the reference bus) > Dr. TAO HUANG > Senior Assistant Researcher > SESAME –Executive vice coordinator > Politecnico di Torino > Dipartimento Energia > Corso Duca degli Abruzzi, 24 > 10129 Torino – Italy > tel. +39 011 090 7117 > fax +39 011 090 7199 > e-mail [email protected] > > > From: [email protected] > [mailto:[email protected]] On Behalf Of Ray Zimmerman > Sent: Wednesday, April 17, 2013 5:52 PM > To: MATPOWER discussion forum > Subject: Re: Modelling transformer and phase shifter > > But as long as the dummy generators are dispatchable and appropriately > coupled I don't see why you wouldn't get an optimal solution for the whole > system (as with our DC line implementation described in Section 6.5.3 of the > User's Manual. > > > -- > Ray Zimmerman > Senior Research Associate > 419A Warren Hall, Cornell University, Ithaca, NY 14853 > phone: (607) 255-9645 > > > > > > On Apr 17, 2013, at 10:35 AM, Tao HUANG <[email protected]> wrote: > > > For power flow maybe yes (neglecting the angle differences and overall system > losses), but for OPF, the optimal result for each island may not be the > optimal solution for the whole system, as the islands are formed purely due > to the replacement of a transformer (or a DC line) by two dummy generators. > > From: [email protected] > [mailto:[email protected]] On Behalf Of Ray Zimmerman > Sent: Wednesday, April 17, 2013 4:30 PM > To: MATPOWER discussion forum > Subject: Re: Modelling transformer and phase shifter > > As long as each island has a voltage angle reference I don't think the > islands should present a problem. > > -- > Ray Zimmerman > Senior Research Associate > 419A Warren Hall, Cornell University, Ithaca, NY 14853 > phone: (607) 255-9645 > > > > > > > > On Apr 17, 2013, at 5:05 AM, Tao HUANG <[email protected]> wrote: > > > > Dear Ray and Kartik, > > Thanks for your reply. I guess the easiest way to utilize the current version > of matpower is to use dummy generators as Ray indicated. But what I concerned > of using this method is the problem of split the network into many islands > when replacing the transformer/phase shifter with 2 generators. If this > happens, we cannot get the OPF/PF results. > > I would also skip using heuristic algorithms as I think they cannot give a > “stable” and “coherent” solution. > > Thanks again for your suggestions. > > Tao > > From: [email protected] > [mailto:[email protected]] On Behalf Of Kartik Pandya > Sent: Wednesday, April 17, 2013 6:35 AM > To: MATPOWER discussion forum > Subject: Re: Modelling transformer and phase shifter > > You may use AI method like PSO to consider TAPS as control variables. > please refer "Optimal reactive power dispatch using Particle swarm > optimization" file at matlab file exchange for more details. > in that file i had optimized TAPS of transformers connected in line no. > 11,12,15, and 36 for IEEE 30 bus test system. > > From: Ray Zimmerman <[email protected]> > To: MATPOWER discussion forum <[email protected]> > Sent: Wednesday, 17 April 2013 12:49 AM > Subject: Re: Modelling transformer and phase shifter > > > It is correct that in the current MATPOWER OPF, the TAP and SHIFT parameters > are fixed input parameters, not variables. I don't think there is a way to > fake it with the AC OPF. That is, I think you really need to include them as > variables in the flow equations and corresponding derivatives. There may be a > way to fake it with dummy injections in the DC OPF, but I haven't really > thought about it carefully. > > Please let us know if you come up with something that works. And of course, > others can feel free to suggest ideas. > > -- > Ray Zimmerman > Senior Research Associate > 419A Warren Hall, Cornell University, Ithaca, NY 14853 > phone: (607) 255-9645 > > > > > > On Apr 16, 2013, at 9:04 AM, Tao HUANG <[email protected]> wrote: > > > Dear Dr. Ray, > > Speaking of the modeling transformer and phase shifter, I would like to see > if the adjustment of the two parameters (tap ratios and shift angles) along > with the generators and loads could get better results of OPF in terms of > cost and convergence (due to the line limits in some cases). do you have any > suggestions as to how to make the tap ratios and shift angles as variables in > the OPF without using iterative calculation (like blindly or using some > heuristic algorithms to modify them and redo the OPF)? If I understand it > correctly, these two values are fixed before the PF & OPF calculation in > terms of Y matrix at present in Matpower. > > I was considering to model the transformer/ phase shifter as two generators > in respect to the flow limits, but it may split the network into two islands > in some cases. So, do you have any suggestion on this as well? I guess it > also applies to the DC line when it is the only connection between two parts > of the network. > > Thanks a lot > > Best wishes, > > Tao > > From: [email protected] > [mailto:[email protected]] On Behalf Of Ray Zimmerman > Sent: Tuesday, April 16, 2013 2:31 PM > To: MATPOWER discussion forum > Subject: Re: Modelling transformer and phase shifter > > Yes, for a transformer you will typically have an off-nominal taps ratio, > i.e. branch(b, TAP) ~= 1 (or 0, which signifies a normal transmission line). > Similarly, if you have a phase shift, you will have branch(b, SHIFT) ~= 0. > > How the transformer TAP and SHIFT parameters affect the amount of load able > to be dispatched depends on the network, so it could go either way. > > -- > Ray Zimmerman > Senior Research Associate > 419A Warren Hall, Cornell University, Ithaca, NY 14853 > phone: (607) 255-9645 > > > > > > On Apr 16, 2013, at 8:18 AM, Jiashen Teh <[email protected]> > wrote: > > > Dear Dr Ray, > > According to your manual , in section '3.2 Branches' > it is mentioned that: > > 'All transmission lines, transformers and phase shifters are modeled with a > common branch model......' > > Does this mean, if I want to include modelling of transformer at a branch, I > would set the column 9 and 10 of mpc.branch which govern the transformer turn > ratio, N ? > > I notice that for values other than zero for both columns (in a manner to > increase N or reduce N), the network (6 bus) will encounter increase of load > not able to be dispatched. Isn't is load dispatch-able should increase? > > Yours sincerely, > > Jiashen Teh > > > > > > > <t_case3_dcline.m><DCline.png>
