Extended Harmonic Resonance Analysis of Grid-Connected Converters Considering the Frequency Coupling Effect
Qiujiang Liu, Yichen Ying, Mingli Wu
Abstract
Existing studies about the harmonic analysis of grid-connected converters (GCCs) mainly focus on the frequency range below Nyquist sampling frequency (NSF) or switching frequency (SF) to make full use of linearization. However, in some actual high-power industrial applications; e.g., electric railways or wind power generation, harmonic problems are challenging in a wide frequency that can be as high as thousands of hertz. This is much higher than the NSF and SF. In order to bridge the gap, this article extends the harmonic analysis frequency to the entire frequency range by addressing the aliasing effect and sideband effect. These two effects can be neglected at the low frequency for simplification while they will make great differences at the high frequency, as demonstrated in this article, due to the frequency coupling and nonlinear characteristics. In this regard, a regression method based on an artificial neural network is used to map the in–out relation of the pulsewidth modulation process. By adopting the methodology of this article, harmonic performances of GCCs can be analyzed comprehensively and explicitly in terms of harmonic instability, harmonic resonance, harmonic overvoltage, filter design, and so on. Finally, experiments are presented to verify the effectiveness and accuracy of the analysis.