A Novel Multiple Fourier Series Modeling for PWM Pulses Formed by Modulation Signals with Time-Varying Amplitude and Frequency

For power grids dominated by renewable energy generation and power electronics converters, high-frequency voltage and current distortion and oscillation are correlated with high-frequency switching internal potentials of converters under pulse width modulation (PWM), which is formed by triangular carrier signal and modulation signals with amplitude-frequency (A-F) interferences. However, due to the applicability and precision, state-of-art PWM analysis methods cannot deal with non-periodic and time-varying A-F characteristics of modulation signals. To solve this issue, a novel multiple Fourier series PWM modeling approach is proposed in this paper, which is based on multiple Fourier series decomposition principle of multivariable periodic function, and can extract A-F characteristics of converter excitation voltage components under PWM with A-F time-varying modulation signals. The effectiveness of proposed method is verified by simulation. This paper will provide more accurate and comprehensive knowledge of PWM pulses, which will be the fundamental of understanding high-frequency harmonics and oscillations in AC grid.