A modified single-phase hybrid cascaded H bridge multilevel inverter with a minimum number of power electronic devices and isolated DC sources is presented in this study. It consists of two inverters (upper and lower) coupled in cascade. The lower inverter is capable of developing a multilevel output and switches at low frequency and another inverter develops two-level output and switches at high frequency. In the proposed inverter, every additional power electronic switch in the lower inverter increases the level by four. This study also introduces a generalised hybrid modulation switching strategy, which gives arithmetical and logical expressions for switching the additional device for any required increase in levels. The voltage rating of the devices, conduction and switching loss of the proposed inverter are compared with the similarly setup topologies. The generalised hybrid modulation algorithm is simulated in MATLAB/Simulink and implemented in a SPATRAN 3A DSP board. Simulation and experimental results are presented for different loading conditions.

This paper presents a new cascaded asymmetrical single phase multilevel converter with a lower number of power semiconductor switches and isolated DC sources. Therefore, the number of power electronic devices, converter losses, size, and cost are reduced. The proposed multilevel converter topology consists of two H-bridges connected in cascaded configuration. One H-bridge operates at a high frequency (high frequency inverter) and is capable of developing a two level output while the other H-bridge operates at the fundamental frequency (low frequency inverter) and is capable of developing a multilevel output. The addition of each power electronic switch to the low frequency inverter increases the number of levels by four. This paper also introduces a hybrid switching algorithm which uses very simple arithmetic and logical operations. The simplified hybrid switching algorithm is generalized for any number of levels. The proposed simplified switching algorithm is developed using a TMS320F2812 DSP board. The operation and performance of the proposed multilevel converter are verified by simulations using MATLAB/SIMULINK and experimental results.