Implementation of Integer Factor based Space Vector PWM through Digital approach for Grid Connected Multilevel Inverters

Abstract

Space vector pulse width modulation control for grid connected multilevel inverters are very popular. However, it gets exceedingly tough with the increase in the number of output voltage levels. The total number of possible switching states will increase with the output voltage level of the inverter. Due to increase in the number of switching states, the sub triangles in the various sectors of the hexagon will also increase, that result in increased complexity and storage requirements for implementation using conventional space vector methods. The objective of the paper is to simplify and generalize the space vector algorithm for an n-level inverter. The proposed algorithm uses integer factor approach to find the exact location of the reference vector, synthesize switching times and generate the nearby switching states. It is a generalized algorithm applicable to any sequence and can be applied to any level judiciously. In this article description of the algorithm is given for a three–level inverter and validated by implementing experimentally using dspace control desk. The PWM signals generated by three level Space Vector algorithm with conventional switching sequence of 0127 is used to control an open end winding induction motor fed with two two-level inverters. The performance factor of motor voltage and line current THD at different modulation index is measured and compared with simulation result.