A Push–Pull Modular-Multilevel-Converter-Based Low Step-Up Ratio DC Transformer

A nonisolated dc-dc converter with chain links of submodules (SMs) is proposed in this paper. The converter can perform as a dc transformer with a low step-up ratio. To demonstrate the step-up dc-dc conversion, the converter is operated in a resonant conversion mode, achieving soft switching and inherent balancing of the SM capacitor voltages. The circuit configuration is presented and the operation principle is analyzed in this paper. Experimental results based on a downscaled prototype validate the performance of the proposed converter as a low step-up ratio dc transformer. The converter also exhibits a good linearity covering a broad range.