Common-Mode Noise Modeling and Reduction Using Gradational Modulation for Solid-State Transformer with Input-Series Output-Parallel Connection

This paper presents a common-mode (CM) noise model for solid-state transformers (SSTs) with input-series output-parallel (ISOP) connection. A gradational modulation technique that combines PWM and square-wave output cells is proposed for noise reduction. The proposed CM equivalent circuit is validated through experimental measurements on an actual SST prototype. Experimental results demonstrate that the gradational modulation effectively reduces CM noise, confirming the effectiveness of the proposed approach.