Simplified Space Vector Modulation Techniques for Multilevel Inverters

This paper presents simplified techniques for the space vector modulation (SVM) of any n-level multilevel inverter. Three techniques have been presented to simplify the identification of the nearest three vectors to the reference vector. The first two techniques are based on resolving the multilevel inverter space vector diagram into appropriate two-level hexagons. This results in simplification of the multilevel SVM problem into a two-level SVM problem. The third technique is an algorithm-based technique which makes use of a 60°-spaced gh coordinate system to perform the SVM of a multilevel inverter. Switching sequence design for all the three techniques is presented with the aim of minimization of the device switching frequency. Simulation and experimental results have been provided to verify the feasibility of the proposed techniques. Simulation results are provided for up to 21-level cascaded H-bridge (CHB) inverters, while the experimental verification is done on a five-level laboratory prototype. Although only the CHB inverter is considered in this study, the proposed techniques are perfectly general and can be applied to all types of multilevel inverters, and are extendable to any number of levels.