Three-Phase AC-AC Converter With Diode Rectifier for Induction Heating Application With Improved Input Current Quality and Coil Modeling

In this article, a three-phase ac-ac resonant converter for an induction heating application is proposed. The system employs three coils in a coaxial arrangement, which is characterized using an resistive-inductive-capacitive (RLC) passive network. For obtaining the parameters of this network, a nonlinear regression from the experimental data was executed using the shuffled complex evolution optimization method, which stands out for its rapid convergence and for providing a well-structured and systematic search for the cost function minimization. The operation stages of the resonant converter are discussed in detail allowing to observe a zero voltage switching (ZVS) behavior for the resonant load inductive region. In addition, the converter operates at unitary power factor because of the smooth dc-link bus voltage and the input current filter. Finally, a 10-kW prototype was built to verify the theoretical analysis and the simulations. As from this comparison was established that the mutual inductance and stray capacitive effects were modeled accurately allowing to reproduce the induced voltages in the coils. Besides, it was corroborated that the coils arrangement influences in the distortion of the input currents, but this distortion can be minimized through the adequate selection of the switching phase angles.