Decoupling output power control of two series resonant inverters sharing resonant capacitor for domestic induction heating

Domestic induction heating applications require an accurate control of the power delivered to the vessel to be heated, ensuring power topology operation under safety conditions. Particularly, this paper is focused on applying a power control of two induction heating loads in a dual-half bridge sharing a common resonant capacitor. This topology leads to a control strategy harder than the classical arrangement which features a dedicated resonant capacitor. A Phase Shift Square Wave Modulation (PSSWM) is performed to control the output powers of the vessels to be heated. Thus, the considered plant is a two-input two-output (TITO) system. The two control inputs are (f_sw, θ) and the two outputs are (P₁, P₂). Since the transfer function matrix is not diagonal, the Relative Gain Array (RGA) methodology is used to analyze if a multi-loop control is feasible. Due to the fact that the system is strongly coupled a centralized control must be applied. Therefore, the aim of the paper is to apply a decoupling control to handle the interactions. Simulation and experimental results in an induction heating prototype are performed in order to validate the proposed control technique.