Role of Chain Inverter to Enhance Power Quality

Abstract

In this paper, a new method of minimizing the input current total harmonic distortion (THD) as well as power factor by using a chain inverter to replace a traditional inverter is presented. This proposal is verified through simulation which uses one type of DC to AC converter with 3-links which can be used to generate seven level output voltage by connecting a number of similar Insulated Gate Bipolar junctions Transistor (IGBT) in series, to form a high Voltage- Source-Inverter (VSI). The main feature of t h i s t o p o l o g y is l ow cost, small size, high efficiency and simplicity, and is excellent for existing ac drives, UPS etc. A new method of implementing stepped voltage waveform proposed here is based on the operation principle of Chain link converter. With reference to the control algorithm, this strategy has realized for seven-level inverter which generates high quality sinusoidal voltage contains lower THD. During one cycle, each IGBT of a CLI switches 'ON/OFF' for a certain time and period using a Sinusoidal Pulse Width Modulation (SPWM) technique. This SPWM technique uses two triangular carrier bands - one positive and one negative - per link, and has a carrier frequency of twice the fundamental frequency and one modulating signal for all links. Simulation is carried out by using MATLAB/SIMULINK which confirms the feasibility of the proposed system.