Modeling of domestic induction heating systems with non-linear saturable loads

In this work, a model for induction heating cooktops with non-linear loads is presented. The model includes both the electronic converter and the inductor-pot system, which is usually modeled by its frequency-dependent equivalent impedance. Due to the non-linear relation between the magnetic field and the magnetic flux density in ferromagnetic media, the equivalent impedance of the inductor-pot system is significantly dependent on the excitation level. In this direction, two common materials have been experimentally characterized by their permeability curve for a wide range of excitation levels. Once the magnetic properties of the materials are known, a simulation model was developed including the non-linear behavior. By means of the simulation model, the equivalent impedance is obtained as a function of the excitation frequency and level. The modeled non-linear load is finally introduced in the power converter model from which the main waveforms can be extracted. Finally, the model was experimentally verified. The system was tested under real working conditions showing good concordance with the simulations.