High-frequency link: A solution for using only one DC source in asymmetric cascaded multilevel inverters. http://dx.doi.org/10.1109/TIE.2010.2103532

Abstract

Multilevel inverters are on the state-of-the-art in power conversion systems due their improved voltage and current waveforms. Cascaded H-bridge (CHB) multilevel inverters have been coincided as an alternative in the medium voltage converter market and experimental electric vehicles. Its variant, the Asymmetrical CHB (ACHB) inverter, optimizes the number of voltage levels by using dc supplies with different voltages. However, the CHB and ACHB inverters require a large number of bidirectional and isolated dc supplies that must be balanced, and as any multilevel inverter, they reduce the power quality with the voltage amplitude. This paper presents a solution to improve the already mentioned drawbacks of ACHB inverters by using a High Frequency Link (HFL) using only one dc power source. This single power source can be selected according to the application (regenerative, non-regenerative and with variable or permanent voltage amplitude). This work shows experimental results of a 27-level ACHB inverter with a variable and single dc source, but the strategy can be applied to any ACHB inverter with any single dc source. As results, the reduction of active semiconductors, transformers and total harmonic distortion (THD) were achieved using only one dc power source.