This paper presents a robustness study of the current
control scheme for a multiphase induction heating system. Resonant
control has been chosen in order to achieve a perfect current
reference tracking in the inductors with different solutions from
the literature. A simplified model of the system is given; it is based
on data extracted from finite-element software, including a model
of the energy transfer between the dc source and the currents.
The metal sheet resistivity will change with temperature, inducing
some modifications in the system parameters. These disturbances
will be rejected by the resonant controllers whose pole and zero
variations are investigated. In addition, the tuning method for
the resonant controllers is detailed when the sampling frequency/
switching frequency ratio is very low. Some specific stability zones
are defined for the resonant controller gains. The application is currently
developed on a test bench devoted to disc induction heating.