Analysis and control of active power filter with optimized injection

The active power filter is the harmonic filter which suppresses the ac harmonics by injecting PWM compensating current into the ac side. The novel model of PWM compensating current Is derived from the optimized injection method. By injecting the derived PWM current, the ac harmonics up to the order of the modulation number are eliminated. With no external source it is possible to build up the inductor current to the desired value, which is limited within the upper and lower limits. The value can be controlled by adjusting the fundamental current flowing Into the filter. Hence the power flow becomes bidirectional In the filter with the optimized injection. The overall characteristics of the proposed method are analyzed theoretically and its validity is proved with the experimental results using microcomputer.