Single-Phase Cascaded-Transformer Converter with Two DC Links

In this paper, a multilevel single-phase converter with injection transformers and two dc links is proposed and applied as an inverter. The basic configuration has five two-level IGBT legs, two injection transformers, one dc source, and one floating capacitor. When isolation is not required, one transformer can be removed. The generalization of the configuration is presented. The calculation of the transformers turns ratios and dc-link voltages to improve the number of voltage levels is provided. The proposed configuration is compared with cascaded H-bridge and a single-phase shared-leg converter with one dc link in terms of several characteristics. Based on semiconductor losses analysis, the proposed configuration is more suitable than the conventional ones for high-voltage low-current applications. Experimental results are shown to demonstrate the feasibility of the system.