Design & Simulation of Transformer less Universal Active Power Filter

Abstract

MATLAB based transformerless universal active filter power quality in power system is presented in this paper. Compared with the conventional H-bridge topology, it only needs two additional asymmetrically distributed switches, and the system common-mode voltage can be kept constant with a simple modulation scheme. The proposed system is a combination of parallel and series active filters without transformer. It is suitable for applications where size and weight are critical factors. The model of the
system is derived and it is shown that the circulating current observed in the proposed active filter is an important quantity that
must be controlled. A complete control system, including pulsewidth modulation (PWM) techniques, is developed. Family of H6 transformerless inverter topologies with low leakage currents is proposed and highly efficient and reliable inverter concept (HERIC) topology is also presented in this paper. The proposed inverter can also operate with high frequency by retaining high efficiency which enables reduced cooling system. Finally, the proposed new topology is simulated by MATLAB/Simulink software to validate the accuracy of the theoretical explanation.

Keywords: Transformer less inverter; Common-mode voltage; Leakage current; Total Harmonic Distortion; Current Ripples; Switching control; PWM.