Three-Dimensional SVPWM using α-β-γ Frame for Solving 4-leg Active Shunt Filter

Abstract

This paper establishes that a three dimensional (3D) space vector pulse width modulation method (SVPWM), using α-β-γ frame, produces better results in four leg (4L) bridge circuit converters used in applications for three phase four wire (4W) low voltage (LT) distribution systems. The algorithm developed has been tested in a 4L active shunt filter (ASF) which helped to reduce harmonics from source currents of a three phase 4W LT distribution system having non-linear and unbalanced load. The ASF also reduces the unwanted component of neutral current. All unwanted components of line currents and the neutral current have been used to generate the 3D reference signal vector to modulate the ASF. Neutral current has been divided in two components, the undesirable and the normal, acknowledging the unbalanced nature of 4W LT distribution systems as a normal phenomenon. The proposed ASF has a unique feature that its bridge circuit capacitor has no need of prior charging to a voltage and to maintain that constant during operations. The MATLAB/simulation of the proposed ASF, working with the developed program, has become simpler in design without phase locked loop or feedback loop and has satisfactory performance.