Asymmetrical duty cycle controlled dual-unit multi-load induction heating system with fixed-frequency ZVS operation

This paper presents a novel dual-unit multi-load induction heating system employing asymmetrical duty cycle control at a fixed switching frequency of 20 kHz. Each half-bridge unit powers three series resonant loads, delivering independent power regulation to six loads simultaneously. The proposed topology is thoroughly validated through comprehensive PSIM simulations and theoretical analysis. The results demonstrate a wide power regulation range of 338–2453 W (7.25:1 turndown ratio) with a quadratic characteristic (P ∝ D 2 , R 2 = 0.998). The minimum duty cycle is D = 0.22, identified as the practical lower limit for maintaining zero voltage switching. The analytical findings and simulation results provide a strong theoretical foundation for experimental implementation. A two-stage convex optimization framework reduces lifecycle cost by 22–28% compared to conventional per-load inverters. Simulation and theoretical validation confirm that the parallel-connected dual-unit topology reduces switching components by half, provides three times greater load density, and can be scaled to 4 units (12 loads). Comparative analysis confirms superior efficiency above 800 W and a wider zero voltage switching range than conventional PWM and phase-shift methods.