Analysis of the Load Current Harmonics Content in a Series Resonant Inverter for Induction Heating Controlled Using Various Cases of the AVC Control Strategy

Abstract

Resonant inverters are widely applied in induction heating applications. A voltage-fed series resonant inverter (SRI) is frequently used as a reliable and cost-effective converter, providing various power control strategies. This paper analyses the load current harmonics content in an SRI for induction heating controlled using particular cases of the Asymmetrical Voltage-Cancellation (AVC) control strategy, belonging to fixed-frequency control techniques. The analysis is carried out for the inverter operation at the minimum values of frequencies guaranteeing zero-voltage switching, and at the fixed frequencies assuring power control in an assumed range of power. Moreover, the impact of the quality factor of the load circuit has been taken into account. The values of the total harmonic distortion (THD) of the load current occurring in Asymmetrical Duty-Cycle (ADC), Phase-Shift Control (PSC) and Asymmetrical Clamped Mode (ACM) control techniques have been determined and compared. The results of mathematical analysis are verified using MATLAB/Simulink simulations. This in-depth analysis and the results obtained are some novel contributions to the existing knowledge of the properties of the aforementioned control strategies of an SRI for induction heating.