Abstract : The interharmonic problem of frequency converters is receiving increasing attention. Taking a common current source frequency converter as an example, this paper analyzes the mechanism of interharmonic generation on the power supply side of the current source frequency converter using harmonic modulation theory and Fourier analysis of the switching function, and establishes a simplified model. The model is verified using a current source variable frequency speed control system and electromagnetic simulation software, and the results confirm the reliability of the model. Keywords : interharmonic; current source frequency converter; variable frequency speed control; modulation theory Based on modulation theory and Fourier analysis of swish function, the mechanism of interharmonics on the source side is analyzed using an example of CSI, and a simple model is established. With a CSI variable frequency drive system, electromagnetic simulation and analysis are performed. The results show that the model is feasible and valid. Keywords : interharmonics; CSI; variable frequency drives; modulation theory 0 Introduction With the widespread application of frequency converters of various capacities, harmonic and interharmonic (including subharmonic) pollution of the power grid is becoming increasingly serious, posing a growing threat to the power grid and equipment. Interharmonics are harmonics of non-integer multiples of the fundamental frequency, manifesting as discrete frequencies or broadband spectra. Besides possessing general harmonic characteristics, they also affect harmonic compensation devices. Currently, research on power grid harmonic pollution focuses primarily on harmonics, with less attention paid to interharmonics. During operation, mismatches in inverter, filter, or power system parameters can cause resonance and interharmonic amplification, leading to the malfunction of some filters, the injection of large harmonic and interharmonic currents into the power system, severe distortion of the system voltage waveform, interference with sensitive electronic control equipment, and disruption of the inverter's own normal operation. Domestic literature on interharmonic research largely focuses on accurately detecting interharmonic frequency components in signals, with limited analysis of the mechanisms and application modeling of interharmonic generation in inverters. [b][align=center]For details, please click: Interharmonic Analysis of Current Source Variable Frequency Speed ​​Control System[/align][/b]