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: <mailto:[email protected]> [email protected] [mailto:bounce-82280449-8559090@ <http://list.cornell.edu/> list.cornell.edu] 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 < <mailto:[email protected]> [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
