Sliding mode PLL-PDM controller for induction heating system


Abstract: In this study, a sliding mode controlled phase locked loop (SMC-PLL) was developed for induction heating(IH) applications with a resonant inverter. PLL applications are widely used in induction heating applications to achievezero voltage switching and zero current switching. In many PLL applications, the frequency tracking is too slow andunreliable. Therefore, a sliding mode controller was developed to provide robust and fast PLL. Furthermore, a pulsedensity modulation (PDM) control strategy was developed to work at the resonant frequency for all power levels. ThePDM power control is a good solution for the design of high-frequency inverters because of a great reduction of switchinglosses and electromagnetic noise. The PDM pattern for the desired output power is determined according to the settemperature value of the work piece. The proposed system was simulated in PSIM and a 250-W laboratory prototypewas implemented with operating frequency of 35-42 kHz.

Keywords: Sliding mode control, pulse density modulation, phase locked loop, series resonant inverter, inductionheating

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