Abstract : Starting with the concept of harmonics and combining relevant knowledge of the internal structure of frequency converters, this paper analyzes in detail the causes and hazards of harmonic generation in frequency converters, proposes common methods for suppressing harmonics, and offers solutions for reference. Keywords : Frequency converter, harmonics, power grid filter, power factor suppression 1 Introduction Frequency converter-driven motor systems are increasingly widely used due to their significant energy-saving effects, convenient adjustment, simple maintenance, and network capability. However, the high-power diode rectification and high-power transistor inversion in frequency converters can generate high-order harmonics in the input and output circuits, interfering with the load and nearby equipment. Harmonics at the input end can also affect the public power grid through the input power line. 2 Basic Concepts of Harmonics The fundamental cause of harmonic generation is nonlinear loads. When current flows through a load, it is not linearly related to the applied voltage, forming a non-sinusoidal current, thus generating harmonics. Harmonic frequencies are integer multiples of the fundamental frequency. According to the analysis principle of the French mathematician Fourier, any repeating waveform can be decomposed into sinusoidal components containing the fundamental frequency and a series of harmonics that are multiples of the fundamental frequency. Harmonics are sinusoidal waves, each with a different frequency, amplitude, and phase angle. Harmonics can be classified into even harmonics and odd harmonics. The 3rd, 5th, and 7th harmonics are odd harmonics, while the 2nd, 4th, 6th, and 8th harmonics are even harmonics. For example, if the fundamental frequency is 50 Hz, the 2nd harmonic is 100 Hz, and the 3rd harmonic is 150 Hz. Generally speaking, odd harmonics cause more and greater harm than even harmonics. In a balanced three-phase system, due to symmetry, even harmonics are eliminated, leaving only odd harmonics. For three-phase rectified loads, the harmonic currents are 6n±1 harmonics, such as the 5th, 7th, 11th, 13th, 17th, and 19th harmonics. Inverters primarily generate the 5th and 7th harmonics. A schematic diagram of the harmonic definition is shown in Figure 1. [align=center][b]For more details, please click: Discussion on Inverter Harmonic Problems[/b][/align]