AC OPF, polar coordinate problem

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Hi all,

I am trying to implement the AC-OPF problem in GAMS (with knitro and ipopt solvers).

There are two versions I created. The first one follows this example https://www.gams.com/latest/psoptlib_ml ... 24bus.html and it works correcttly and give a correct solution.
In the second version, I tried to follow the model in this paper https://www.tandfonline.com/doi/epdf/10 ... ccess=true
Here I used Eq (5)- Eq (11) and Eq (57) - Eq (58) for the power flow equations. This version keeps getting infeasible solution (it should have yielded the same solution as in version 1)

I have attached my GAMS codes for your references. Your help would be greatly appreciated.

Thanks,

Andy