Control Configurations for Reactive Power Compensation at the Secondary Side of the Low Voltage Substation by Using Hybrid Transformer

Abstract

The high penetration of new device technologies, such as Electric Vehicles (EV), and Distributed Generation (DG) in Distribution Networks (DNs) has risen new consumption requirements. In this context, it becomes crucial to implement a flexible, functional and fast responsive management of the voltage level and Reactive Power (RP) in the DN. The latest improvements in the Solid State Switches (SSS) field demonstrate they can be used as a Power Electronic (PE) converter. In particular, they have been shown to be capable of operating synchronously with transformers, making the Hybrid Distribution Transformer (HT) concept a potential and cost-effective solution to various DN control issues. In this paper, a HT-based approach consisting of augmenting the conventional Low Voltage (LV) transformer with a fractionally rated PE converter for regulating and controlling the RP in the last mile of the DN is proposed. In this way, it is expected to meet the demand of the future DN from an efficiency, controllability and volume perspective. The proposed approach is implemented using a back-to-back converter. In addition, a power transfer control topology is used to implement the proposed control of the RP injection that controls the voltage level at the Direct Current (DC) link. The proposed approach has been demonstrated in different load scenarios using the Piecewise Linear Electrical Circuit Simulation (PLECS) tool. The simulation results show that the proposed approach can compensate the loads with their need from RP instead of feeding them from the transmission grid at the primary side of the Distribution Transformer (DT). In this way, the proposed approach is able to decrease the transferred amount of RP in the transmission lines.