High-Frequency Soft-Switching AC Conversion Circuit With Dual-Mode PWM/PDM Control Strategy for High-Power IH Applications

This paper presents a novel high-frequency soft-switching power conversion circuit for high-power induction heating (IH) applications such as the following: (1) heat treatment of metals; (2) hot water; and (3) superheated steam producers. This high-frequency power conversion circuit can operate from single-phase or three-phase systems to produce high current for high-power IH applications under the principles of soft-switching operation. It can regulate its ac output power from the rated value to a low power level. A dual-mode control scheme based on high-frequency pulse width modulation (PWM), in synchronization with the utility frequency positive and negative half-cycles, and pulse density modulation (PDM) is proposed to extend the soft-switching operating range for wide-output power regulation. A dual-pack heat exchanger assembly is designed to be used in consumer and industrial fluid pipeline systems and it is proved to be suitable for hot water, steam, and superheated steam producers. Experimental and simulation results are given to verify the operating principles of the proposed power conversion circuit and to evaluate its power regulation and conversion efficiency.