IEEE standard DC exciter (DC4B)

Hello, I need a MATLAB code for DC exciter DC4B. I solve this through simulink but I need a m file.

OR

Anyone give me some direction how to solve this through MATLAB coding. Here is the screenshot of set of diffrential equations of this exciter. I know how to use ode23 and ode45 solver to solve diffrential rquations but I couldn't able to solve these equations due to one laplace term VPID (highlighted in yellow colour). Please someone guide me