The harmonic control technology of active filter equipment is one of the effective means to improve the quality of power supply. After the popularization and application of APF in the power supply system of hospital buildings, the generated harmonics can be controlled within the minimum range. Realize scientific and rational use of electricity, restrain grid pollution, improve power quality, ensure the safety of medical equipment, and bring huge economic and social benefits to users.

The fundamental cause of harmonic generation in low-voltage power supply systems is due to the nonlinear characteristics of certain equipment and loads in the power grid (such as high-power rectifier equipment, thyristor rectifier equipment, frequency converters, electronic ballasts, and computers). Because these electronic rectifiers have commutation problems, and their loads are non-linear loads. That is, the waveform distortion caused by the non-linear (proportional) relationship between the applied voltage and the generated current.