Spread Spectrum Modulation Techniques for EM Noise Reduction in Hybrid Distribution Transformers

Abstract

This paper analyzes the EM noise reduction performance and effectiveness of a Hybrid Distribution Transformer (HDT) using Spread Spectrum Modulation (SSM). The HDT consists of a conventional Low-Frequency Transformer (LFT) and a power converter handling partial power. Based on this structure, the HDT can supply high-quality power to the grid while offering reliability and cost efficiency. However, EM noise generated by the high-speed switching of the power converter adversely affects the grid. Passive EMI filters are commonly used to mitigate EM noises; however, they have the disadvantage of reducing power density and efficiency. To address this issue, the paper designs and applies an effective SSM to the HDT, evaluates its EM noise reduction performance, and analyzes its side effects. The noise reduction performance and analysis of the proposed SSM operation in the HDT are experimentally verified using a 5-kW prototype.