Simplified THD measurement and analysis for electronic power inverters

Quality of audio and power signals is often measured in terms of their total harmonic distortion (THD). In this study, we measure THD using simple tunable high-Q active analog filters. We model analog filters for THD measurement at 500Hz and analyze their responses. We implement these filters using general purpose electronic components to compare with reference distortion values by analyzing the harmonic content. We develop a procedure to measure THD using oscilloscope and analog filters for fixed frequencies. Our results demonstrate that it is sufficient to consider second and third harmonics in most cases to obtain a practically accurate value of THD.