Try first to get the model of your power system. The model could be in the form of a transfer function with one input and one output for simplicity.

The transfer function could be integer-order or fractional-order. It is your choice.

This will make your system a fractional-order system.

If you have an integer-order system, then there is no need to have a fractional-order system unless otherwise you want to be very accurate with your model. Usually, given a fractional-order system, the integer-order approximation is then obtained, not the other way around.

In essence, fractional-order would make your life more difficult therefore if you have an integer-order system and you're already satisfied with the model, then just stick with it. But if you really need a more-accurate fractional-order model, then you need to perform another round of system identification. You may check this (https://www.researchgate.net/publication/259296494_Identification_of_Fractional-Order_Dynamical_Systems_Based_on_Nonlinear_Function_Optimization).

Article Identification of Fractional-Order Dynamical Systems Based o...