Study of the Effect of Higher-Order Harmonics on the Frequency Response Analysis of Series Resonant Converter

This paper presents an investigation of the influence of higher-order harmonics on the frequency-response characteristics of a full-bridge series-resonant DC-DC converter.A Fourier series-based analytical method is developed to include these harmonics, providing a more accurate representation of voltage and current waveforms within the resonant tank, as well as in the converter input and output.The frequency characteristics, total harmonic distortion (THD) and ripple factors of the converter are derived for various quality factors and normalized frequencies using GNU Octave for computational modeling.The results reveal that the higher-order harmonics considerably affect the shape and amplitude of the resonant current, especially below the resonant frequency.Experimental validation using a laboratory prototype demonstrates good correlation with the theoretical predictions obtained by the Fourier series analysis, whereas the FHA method shows noticeable deviations.The proposed approach offers improved precision and can serve as a practical tool for the filter design and performance optimization of resonant power converters.