Control of Induction Heating Inverter

Induction Heating Inverter

The industry strongly relies on PI controllers for induction heating inverters due to their simple design. Because correct load parameter estimation is almost impossible and their effect over electrical variables is not negligible, as it is presented in the paper, it is necessary a variation tolerant control algorithm. The present work proposes such advanced algorithms, based on different augmented plant models and on H∞ design method. The paper also focuses on the practical approach of the controller implementation on an experimental pilot. The advantages of the robust controller are justified by simulation results and experimental data, as compared to the classical PI controller solution. Induction heaters are modern, economic and environment friendly equipments. The heated work-piece is placed in an inductor, which generates high intensity electromagnetic field inducing eddy currents. Through Joule-Lenz effect of these currents heat is generated directly in the working material. For a given inductor and workpiece geometry, the heating profile strongly depends on the skin and proximity effects, which are influenced by the physical properties of the heated material [1]. For low power (<25kW) and high frequency (>10kHz) applications, inverters with series resonant load are preferred due to their simple design. The output inverter variables (load current, developed power, capacitor voltage or phase shifts) can be controlled through inverter supply voltage, or through driving strategies of the power transistors of inverters.

Control of Induction Heating Inverter

Control of Induction Heating Inverter.pdf