Stability Analysis of a Hybrid Distribution Transformer with a Series/Parallel Converter Connected to the Primary/Secondary Side

Hybrid Distribution Transformers (HDTs) have been proposed as a promising solution to power quality issues in distribution networks. HDTs combine a classical Low-Frequency Transformer (LFT) with a series and parallel connected power converters. In this paper, the stability of HDT is analyzed using their equivalent impedance/admittance models. This paper considers that the power converters are decoupled by the DC-Link, which simplifies the analysis. The stability is assessed using the Generalized Nyquist Criteria (GNC) and the singular value decomposition. The results show that the HDT is stable when each power converter is designed with proper stability margins and due to the power converters partial power operation.