A Single-phase Active Power Filter with an Improved Modulated Carrier Control

Abstract

This thesis proposes a new control method, improved modulated carrier control, for single-phase active power filter which eliminates harmonic and reactive currents at ac sources drawn by nonlinear loads. The new control method directly shapes line current to be sinusoidal and in phase with grid voltage by comparing a modulated carrier signal to the average line current and making duty ratio doubled. Since the line current value compared to the carrier signal is not the peak, but the average, dc-offset problem observed in a similar type of control method is effectively enhanced. The proposed control technique extirpates the harmonic and reactive currents properly and solves the dc-offset problem. The operation of a shunt active power filter with the proposed control method is discussed and design guideline is given in detail. Experimental results on the basis of laboratory prototype hardware verify its performance.