Dear Mahdieh,

welcome,

Eid Mubark,

I will answer this question from the conceptual point of view.

Loads are represented by ohmic resistor R. The power in an ohmis resistance is P= V^2/R. In order to make P constant independent of V one has to make R a nonlinear resistance whose value is proportional to the square of the applied voltage on its terminal. That is R= KV^2. Substituting in the equation of power we get:

P= V^2/ K V^2= 1/K, so, K is equal to the inverse of the constant power required.

So, constant power loads can be modeled by a nonlinear resistance whose value is proportional to the square of its terminal voltage.

Best wishes

Thank you for your comment.