Recently,it is increasing to concern on power quality. There are many factors causing poor power quality. Harmonic is the one of the serious problems. So power electronic technique is required to a distribution power system. Active Power Filter (APF) is used for compensating harmonic.
We control APF using a Digital Signal Processor. So there always exists a sampling delay between reference and real value. In this reason control performance is not good. To overcome this problem a new prediction algorithm is proposed.
Proposed prediction algorithm is using IIR (Infinite Impulse Response) Filter. Assuming a steady state, current command of q and d axis is periodic every 60 degrees in the 3-phase balanced electric system. So we can store this current command. When k-th interrupt signal is occurred, we get a k-th harmonic reference. Also we know past reference in the 60 degrees. Using a IIR Filter, we update a harmonic reference. In other words we can control a IIR Filter coefficient, namely weighting factor. In this prediction algorithm, we get (k+2)-th harmonic command when k-th sampling occurs. So efficiently solve the 2-sampling delay problem.
The effectiveness of prediction algorithm using IIR Filter is demonstrated by experiments. This algorithm is used for shunt active power filter.
