Research on Control Strategy for Three-Phase Three-Wire Shunt Active Power Filter under Unbalanced Loads

To solve the problems caused by unbalanced load in industrial fields, two novel methods to extract harmonic current and reactive current and a 2/2 transformation matrix are proposed based on instantaneous power theory, enabling APF to extract base positive sequence current, base negative sequence current and other high order harmonic current correctly and timely, thus we can choice compensation strategy flexibly according to the rated capacity of APF-cancelling none but high order harmonic current in the field with base negative current beyond the rated capacity of apf, while in the case of small current, including base negative current and high order harmonic current, lower than the rated current of apf, compensating all but the base sequence current. Theoretical study with Matlab simulation and experimental results demonstrate that the methods are feasible and very useful in industrial fields.