Chua’s model of nonlinear coil in a ferroresonant circuit obtained using Dommel’s method and grey box modelling approach

Chua’s model of the nonlinear coil is often used in ferroresonance research. In this paper, two methods are used to determine such a model: usual Dommel’s method and a grey box modelling approach, which is a novel way to model the nonlinear coil in a ferroresonant circuit. The parameters of the grey box model are determined by nonlinear regression using a metaheuristic optimization algorithm. The obtained models are evaluated by comparing the steady-state types obtained by measurements with those obtained using simulation. Comparing the obtained Chua’s models, results indicate that the grey box modelling approach is more accurate than Dommel’s method for lower coil nominal voltage. However, the main conclusion is that Chua’s model in general cannot be used to predict all steady-state types typical for ferroresonance, i.e. it can be used in a highly restricted manner for appearance of certain steady-state types only.