Dear Mr. Zimmerman, I am a graduate student in Applied Mathematics at Delft University of Technology. Though it is not a part of my major, I am currently involved in a project at the Optimization group of the faculty of Electrical Engineering, Mathematics and Computer Science that deals with a large optimal power flow problem. In the project, Matpower is the package of choice. I was assigned the specific task to make Matpower work with adjustable tap ratios for transformers.
My superiors told me that adjustable transformers are not currently supported by Matpower, but that you wish to implement this somewhere in the future. I would like to let you know that I have made an effort in this, so that it could be used for our project. Maybe it could be of some value for you. To include adjustable transformers I manually added two more variables to the OPF problem: the tap ratio and phase shift angle of the transformers. Since the Ybus matrix depends on these variables, I had to calculate the Jacobian and Hessian of the power balance and flow limit constraints with respect to these new variables. I put these calculations on arxiv: http://arxiv.org/abs/1311.5115 In the near future I will also make them available on my university website as a technical report. The implementations themselves were only to be used by myself, and for a specific testcase. At the moment, the implementation is by no means robust, and also not user-friendly. It might also contain errors. Therefore, I have not made the code available online. If you would like any changes to be made to the arxiv document, or if I need to take any other action regarding this, please let me know. Otherwise, you can just consider this message as a notification. Thank you for your time. Yours sincerely, Laurens Bliek
