A High-Power Two-Port Multiple-Frequency <i>LLLC</i> Induction Heating Power System

A new high-power two-port multiple-frequency <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLLC</i> induction heating power system is proposed in this article, which can simultaneously achieve multiple-frequency, multiple-power, and high-efficiency output. A two-port <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LLLC</i> resonant tank with an inverter at each port is used to power the load. The multiplication of output power and frequency is achieved by coordinating the operating modes of the two inverters. In order to improve the efficiency of the system, a design methodology for tank parameters is proposed, ensuring that the system operates at the optimum point of efficiency, thereby avoiding reactive power losses and realizing zero voltage switching (ZVS). Additionally, an adjusted-pulse density modulation (PDM) (APDM) control method is proposed, which can further enhance the efficiency of PDM control. The shortcomings, such as large current fluctuation and the tendency to lose lock, are optimized, allowing the system to operate with high efficiency across the full power range. Finally, an experimental prototype (SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small>) is developed to verify the feasibility of the topology, parameter design methodology, and APDM.