Towards a smart distribution transformer for smart grid

In this paper, a smart distribution transformer which addresses power quality issues in the electrical power distribution system is presented. The proposed system is comprised of a line frequency transformer connected to a power electronic converter that is `auto-connected´ on the secondary side. The auto-connection is facilitated by the use of a high-frequency (HF) / medium frequency (MF) transformer. A simplified strategy to compensate for voltage sags, swells, and distortions on the grid side, by providing continuous ac voltage regulation, is discussed. When a voltage disturbance event occurs, the power electronic converter generates a compensating voltage, which is vector-added to the grid voltage in order to regulate the output voltage supplied to the load. The smart distribution transformer will satisfy the various needs of the present and future distribution smart grid such as improved availability, equipment protection, and resilience. This paper provides detailed analysis, simulation results and experimental results from a scaled down laboratory prototype rated 200 W are also presented to validate the operation of the proposed smart distribution transformer.