As more and more non-linear loads have been applied to industrial manufacture, power system has been suffering from severe harmonic pollution. Frequently-used industrial means to inhibit harmonic distortion is passive power filter. However, there are some irreducible shortcomings. For example, compensation effects rely on loads; its usage is inflexible; it is easy to trigger parallel and series resonance, etc. Active power filter is the substitute of passive power filter. AVIC-Tech active power filter (APF), with advanced design ideas, flexible module configuration, remarkable working performance and merit outcomes, has been applied widely in many industries to resolve effectively problems of harmonic waves.