FPGA-Based Hybrid Control Strategy for Resonant Inverter in Induction Heating Applications

An implementation of a fully digital control system for driving resonant power converter is a challenging task. Furthermore, solving discrete-time equations on a digital platform like field-programmable gate array (FPGA) device being used for its fast response characteristic along with the real-time validation is an additional prominent challenge. This article aims at solving both the challenges for a series resonant inverter used in solid-state induction heating (IH) application. The proposed hybrid control strategy is aimed at phase-shifted pulsewidth modulation to achieve output power regulation and pulse frequency modulation control to maintain soft switching for dynamic load conditions, simultaneously. The performance of the controller is investigated under varying load and power conditions. An improvement in the overall control performance is ensured by introducing a dynamic slope compensation logic with digital blocks. The simulation-based modeling of control system and proportional–integral–differential tuning methods are presented. Furthermore, the proposed controller is validated by hardware-in-the-loop simulation for FPGA implementation and tested experimentally on a laboratory prototype of 5-kW IH system for metal melting applications, using Zynq XC7Z020-1clg484 FPGA platform.