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
