Abstract: This paper introduces the basic concepts of power quality, the causes of circuit distortion, and the load characteristics of water plants. The harmonic pollution of pulse and pulse thyristor rectifier circuits is analyzed. The harmonic pollution of the high-power frequency converter at the Chengbei Water Plant is tested and analyzed, and solutions are proposed. Keywords: Distortion; Harmonic; Frequency converter; Active filter 0 Introduction With the rapid development of power electronics technology, the winding loads of various power electronic devices, such as rectifiers, variable frequency speed control devices, electrified railways, electric arc furnaces, motors, and transformers, are constantly increasing. On the one hand, due to the nonlinear, switching, and unbalanced power consumption characteristics of these loads, harmonics, three-phase voltage imbalance, and flicker in the power grid are becoming increasingly severe, causing serious pollution to power quality. On the other hand, the increase in a series of energy storage loads such as motors and transformers in the lines consumes a large amount of reactive power. These power problems not only seriously pollute the power quality and affect the normal operation of electrical equipment on the lines, but also generate a large amount of line losses and cause line overload accidents. 1. Harmonics Under ideal conditions, when a three-phase power system is operating, it supplies power to users at rated voltage, rated frequency, and phase. The voltage and current waveforms are standard sine waves, and the voltage can be expressed as: [b][align=center]For more details, please click: Research on Harmonic Pollution from High-Power Frequency Converters in Water Plants[/align][/b]