Interharmonic Source Model for Current-Source Inverter-Fed Variable Frequency Drive

This paper presents a concise frequency-domain interharmonic model for the current-source inverter-fed (CSI-fed) variable frequency drives (VFDs). This model is in the form of a Thévenin equivalent circuit. The equivalent voltage source is determined only by the VFD operating point, while the equivalent impedance is influenced by the system impedance, the dc-link impedance, and motor parameters. This model, verified by simulations and measurements, can be used to predict the interharmonic propagation in a system supplying CSI-fed VFDs. The model also reveals the interharmonic generation characteristics of the VFDs, which will help the proper selection of mitigation options. Based on the model, the analysis of the nature of the interharmonic source of CSI-fed VFD has been conducted. Some applications are demonstrated as well.