Active Power Filter (APF) is a new type of power electronic device used to dynamically suppress harmonics and compensate for reactive powerlessness. It can compensate for harmonics that change in size and frequency and reactive power.
Active filters are called active. As the name implies, the device needs to provide power supply (to compensate for the harmonics of the main circuit). Its application can overcome the shortcomings of traditional harmonic suppression and reactive power compensation methods such as LC filters (traditional only fixed compensation), realize dynamic tracking compensation, and can make up both harmonics and reactive power.
The instantaneous reactive power theory of three-phase circuits is the main basic theory for the development of APF; there are parallel and series types, and the former is mostly used; parallel active filters are mainly used to control current harmonics, and series active filters are mainly to control problems caused by voltage harmonics. Compared with passive filters, the active filter has a good governance effect. It can mainly filter out multiple and high-order harmonics at the same time, which will not cause resonance, but the price is relatively high!