Analysis of High-Frequency Parallel Quasi-Resonant Inverter Performance in Induction Heating Systems under Variable Switching Frequencies

Abstract

The performance of high-frequency parallel quasi-resonant (HF-PQR) inverters in induction heating systems critically depends on the switching frequency, resonant tank design, and load conditions. This study presents an in-depth analysis of HF-PQR inverter behavior under variable switching frequencies, emphasizing efficiency, load current stability, harmonic distortion, and thermal performance. A comprehensive evaluation was conducted using both theoretical modeling and simulation, with experimental validation drawn from previously established literature. Results indicate that resonance alignment is paramount for optimal operation, with peak efficiency exceeding 92% at nominal resonant frequency. Deviations from resonance significantly degrade performance, resulting in efficiency losses up to 15%, elevated harmonic distortion, and increased thermal stress on switching devices. Comparative analysis between half-bridge and full-bridge topologies revealed that full-bridge configurations provide superior off-resonance resilience, supporting enhanced load adaptability, while half-bridge designs, despite their simplicity and compact footprint, require precise frequency control to maintain stable operation. The integration of load-adaptive control algorithms, such as Pulse Frequency Modulation (PFM), effectively mitigates performance degradation by reducing RMS current fluctuations and harmonics under off-resonance conditions. Furthermore, the study identifies critical operational limits and practical considerations for domestic and industrial induction heating applications, including thermal management strategies, protection circuit design, and dynamic resonance tracking. The findings contribute to a deeper understanding of HF-PQR inverter dynamics, providing actionable insights for the design, optimization, and control of induction heating systems that require high efficiency, stable energy transfer, and reliable operation under variable operating conditions. These results are supported and contextualized by established literature on quasi-resonant inverters, load-adaptive control mechanisms, and high-frequency induction heating technology, highlighting the importance of integrating theoretical modeling with practical design considerations to achieve superior performance. Overall, this work establishes a comprehensive framework for evaluating and optimizing HF-PQR inverters, advancing both academic understanding and industrial implementation of high-efficiency, high-performance induction heating systems.