Abstract : This paper analyzes the generation principle, interference pathways, and common hazards of high-order harmonics in frequency converters. Based on the author's experience, several methods for suppressing high-order harmonics are described. Keywords : Frequency converter; High-order harmonics; Interference; Hazards; Suppression 0 Introduction With the development of power electronics technology, the application of high-frequency switching devices in power electronics technology is becoming increasingly widespread, bringing huge benefits to society. However, when the mains frequency power supply passes through a frequency converter composed of thyristors for rectification and inversion, harmonics are generated. These harmonics damage surrounding equipment and the power grid (these harmonics usually refer to high-frequency components below the 50th order). For frequency converters controlled by PWM, the harmonic frequency is related to the frequency converter's modulation frequency: if the modulation frequency is low (1-2kHz), the human ear can hear electromagnetic noise (screaming sound) generated by several high-order harmonic frequencies; if the modulation frequency is high (such as IGBT frequency converters reaching 20kHz), although the human ear cannot hear it, the high-frequency signal still objectively exists. A P-pulse frequency converter generates harmonics of the order m=pn±1 (where n=1, 2, 3…). Therefore, the harmonic orders generated by a 6-pulse frequency converter are 6n±1=5, 7, 11, 13…, while the harmonic orders generated by a 12-pulse frequency converter are 12n±1=11, 13, 23, 25…. The theoretical value of the harmonic content of the composite phase current with a shape close to a square wave is I/m. Due to the smoothing effect during commutation, the actual value is smaller than the theoretical value. High-order harmonic interference on the output side of the frequency converter occurs through two paths: conduction and radiation. Harmonics are conducted through wires, and during conduction, wires laid parallel to the frequency converter output line will generate electromagnetic coupling, forming induced interference. High-order harmonics on the output side of the frequency converter will radiate, interfering with nearby wireless equipment. [b]2 Hazards of High-Order Harmonics on the Output Side of the Frequency Converter 2.1 Impact of High-Order Harmonics on Equipment[/b] [b][align=center]For details, please click: Hazards and Suppression Methods of High-Order Harmonic Interference from Frequency Converters[/align][/b]