Hybrid Distribution Transformer Based on an Existing Distribution Transformer and a Series-Connected Power Converter

Abstract

This article proposes a new architecture for the hybrid distribution transformer (HDT) with a partially rated power converter connected in series with the existing distribution transformer. The proposed single-phase system is constructed by adding a three-legged power converter in series to the existing transformer’s primary side. Here, the way the converter is connected to the transformer's two taps provides the following advantages: 1) It is possible to reduce the power converter’s power rating, and 2) An additional current loop, which gives a degree of freedom, is added. For better power quality, the proposed system synthesizes a voltage vector to compensate for the voltage sags/swells and the grid voltage harmonics. Furthermore, it improves the grid’s power factor to increase the power transmission efficiency. The proposed system meets the needs of smart grids in terms of resilience. The configuration, control strategies, analysis, and activation/deactivation sequence of the proposed system are discussed in this article. Real-scale simulations and lab-scale experiments were performed to validate the proposed system, and the system's effectiveness was verified through the obtained results.