An implementation method for hysteresis-band current tracking for active power filter (APF) based on digital over-sampling is proposed

which enables precise compensation of harmonic current and stabilizes the switching-frequency. This method can meet different dynamic response demands of control and operation modules by utilizing different extraction factors of digital chip over-sampling. And it fully coordinates two kinds of operations in the digital signal processor (DSP)

the sampling interrupt operation and main loop operation

which ensures real-time harmonic current detection and synchronous tracking for the compensating current.The same reference will be tracked N times and the change of power switching device status depends only on the parameters of the preceding switching-period

resulting in high precision tracking for current. Compared with the traditional hysteresis-band current control method

the proposed method has 0the advantage of not only stabilized switching-frequency but precise harmonic compensation as well

proving its applicability and reliability. A 65 kVA experiment system for three-phase three-wire APF is built for verification and the validity of the proposed method is confirmed by experimental results.