Performance of Three-Phase Asymmetric Cascaded Bridge (16:4:1) Multilevel Inverter

Availability of more number of levels for the same number of switching devices has made asymmetrical topologies superior over symmetrical structures. While the 16 : 4 : 1 configuration is reported as an optimal asymmetry, a detailed performance is not available in literature. This paper presents the performance and control of the 16 : 4 : 1 asymmetrical topology. A new analytical approach is introduced to find the complete information of the available combination of space vectors for any asymmetric ratio. A limit chart is introduced, which represents the number of ways to generate a particular space vector. Asymmetrical hexagonal decomposition technique is used to select the switching devices from the high-, medium-, and low-voltage cells to realize a space vector. The converter is simulated in MATLAB/Simulink. Supporting results from a laboratory prototype have confirmed the usefulness of the 16: 4: 1 asymmetrical configuration.