A Novel Shunt Active Power Filter Under Condition of Unbalanced Voltage

Two methods for detecting harmonics and reactive currents: p-q theory and ip-iq theory, which are based on three-phase instantaneous reactive power theory, are presented. The model of shunt active power filter(APF), based on the two methods in MATLAB, is built. In the model, the root-mean-square (RMS) part takes place of the low pass filter (LPF) part. But the two methods can´t work properly when the three phase voltage does not balance. Then a new method has been proposed, and the result of simulation verifies that the method is correct.