Analysis of Harmonic Compensation for Grid-side Current of Series Sixfold-circuit “Phase-hopping” AC-AC Frequency Converter

Abstract

Background: A series sixfold-circuit “phase-hopping” AC-AC frequency converter (SSCPH-AAFC) is an extension of traditional AC-AC frequency converters. Compared to traditional frequency converters, it has the advantages of energy-saving, low cost, and simple control. Additionally, it can increase the upper limit of the frequency conversion to the power frequency. Through multiplexing processing, it reduces the harmonic content of the output waveform, making it suitable for applications, such as large-capacity fan or pump speed control. Objective: Although SSCPH-AAFC reduces harmonic content, the harmonic content of the single- phase and three-phase grid-side currents still reach 14.65% and 10.20%, respectively. To meet national standards for practical application, a compensation circuit needs to be designed to further reduce grid-side current harmonics. Methods: To address harmonic problems, a targeted single-phase current open-loop compensation method was designed based on the analysis of the current waveform defect. The method compensated for harmonics by selecting appropriate trigger angles and reducing the harmonic distortion rate of the power grid to meet the necessary application standards. Results: The method was simulated and analyzed using MATLAB, and the results showed that after single-phase open-loop compensation, the total harmonic distortion (THD) of the grid-side current for a single-phase SSCPH-AAFC was 2.64%, and for a three-phase SSCPH-AAFC, it was 1.80%. Conclusion: This method has a good effect and can meet the standard requirements.