Selective harmonic current mitigation with shunt active power filter

The paper presents three methods of selective harmonic compensation with shunt active power filters in different reference frames: harmonic dq-frame, stationary frame and fundamental dq-frame; and shows that the last two methods are derived from the first one. By analyzing their advantages and drawbacks, the paper shows that the last two methods have a more compact mathematical representation which may extend to straightforward DSP implementation. However, the first method, i.e. selective compensation in harmonic dq-frame, is more flexible and allows a better tuning and adjustment, which is of a great importance in practice. For experimental tests only the selective harmonic control in fundamental dq-frame is presented, to demonstrate the selectiveness harmonic current compensation. The experimental results are performed in laboratory conditions on a 7 kVA active filter prototype, indicating a reduction in current THD_i factor from the existing 27% to 2%.