Research On Harmonic Detection And Deadbeat Control For Shunt Active Power Filter

As harmonic has been the most deleterious factor in power quality, many scholarspropose different means to restrain it. Nowadays as the most effective means for harmonicsuppression, APF mainly has two sides of key technologies: harmonic detection algorithm,and tracking control strategy. This paper offers all the theories and methods based on themathematical models of shunt active power filter.On the one hand, in consideration of the delay caused by LPF in ip-iq harmonic currentdetection, the paper presents anther method which uses the integral combined with Fourierdecomposition and delay link replacing the traditional LPF. At the same time, the method canbe flexibly applied to an unbalanced three-phase system, only after simple trigonometricfunction transformation. Compared with the traditional one, the proposed method can reducesome delay greatly, whenAPF put into operation.On the other hand, abandoning the traditional track control method, the paper putsforward a predictive control method for compensation current control, deadbeat control,which transfers current control into voltage control though establishing state equation of themathematical model based on the three-phase three-wire APF system, in digital system,combined with the voltage space vector pulse width modulation. Use two beats of repetitivecontrol algorithm to achieve the harmonic real-time compensation, after transforming theforecast of harmonic into prediction of current load. The DC voltage control uses a simple PIcontrol to realize the stability of DC capacitor after selecting appropriate parameters.Finally, build simulation model of APF in Matlab/simulink, and compare the differentresults of traditional and improved method presented in this paper. The results illustrate theaccuracy of the detection method proposed in this paper as well as the effectiveness of controlstrategies.