DC-DC converter small signal modelling

This function generates the small-signal model of a 2 discrete state DC-DC converter.

DC-DC converters have a different number of discrete states depending on the position of their switches (on or off). The aim of this function is to generate the small-signal model of a 2 discrete state DC-DC converter by employing the symbolic engine of Matlab. Based on the equations of the book "Fundamentals of Power Electronics" (Erickson and Maksimovic, 2001), first the average model of the converter is obtained and then it is linearized in order to generate the transfer functions of the small-signal model. The function outputs the transfer functions of the output with respect to the inputs as well as the duty cycle of the converter in a symbolic form.
The inputs of the function are the discrete state matrices in a cell form mA = {A1;A2}, mB = {B1;B2}, CA = {C1;C2} and mD = {D1,D2}, and the state variable (X), input parameter (U) and output parameter (Y) vectors.
The validation file attached shows three examples for a buck, boost and buck-boost converter with parasitic elements where this function is employed. Some of the parasitic elements are set to 0 not to take them into account in the small-signal model. However, these lines of code can be commented to include them in the model.