Constant output power control of three-phase inverter for an induction heating system

This paper presents a three-phase constant output power control scheme of an induction heating system using an automatic variable-frequency symmetrical voltage-cancellation (AVFSVC) control technique. The control scheme is based on a product of current and voltage in the induction coil. The resulting instantaneous output power is filtered and compared with a reference value. The output power can be automatically adjusted according to the power requirements by varying the duty cycle of switches where the power control range is expanded. The operating frequency-tracking is controlled by a phase locked loop (PLL) control for maximum overall system efficiency. The switches operate under zero voltage switching (ZVS). The validity is verified through the simulated results on the output power ranging from 0.03 to 16.5 kW under 15.12 to 16 kHz operation frequency.