3-Phase Back to Back Active Power Filter for a Multi-Generator Power System with Reduced dc-link Capacitor

A single wye-delta (Y-Delta) shunt transformer front-end for a multi generator power architecture has been gain more and more attention. It provides comparable 5th and 7th harmonic elimination performance to the conventional 12-pulse rectifier with a much-reduced transformer size. However, the shunt transformer rectifier is not able to eliminate 11th and 13th harmonics due to its harmonic cancellation mechanism and the harmonic cancellation performance is sensitive to the transformer leakage inductance. In this paper, a back-to-back active front-end is proposed to improve the drawbacks of the existing shunt-type front-end. PI+R compensator is introduced for the current loop and it effectively eliminates up to 19th harmonics in ac mains. Furthermore the relationship between the phase shift angle between the genset-pair and the dc bus voltage ripple is analyzed and the phase-shift angle that minimizes the dc bus voltage ripple is derived to reduce the required bulk capacitor size. The prototype design achieved 3.14 % THD while 96 % and 66 % reduction in weight and overall volume respectively, which makes it extremely beneficial to large-scale industrial and shipboard applications.