Harmonic reduction in three phase unbalanced systems

Active power filters are becoming more and more economically viable as a solution to reduce harmonics generated by nonlinear loads. In the shunt connected conventional three-phase topology, interactions between phases are experienced. This problem points to the necessity of having per phase based current controllers and power converters. The three half-bridge topology presented in this paper is a solution to this problem: it uses three single-phase modules with a center tap capacitor. It allows control of individual phase currents and operates under constant switching frequency. Theoretical analysis of the circuit is included, and experimental results are presented to validate the analysis.