Smart transformer universal operation

The Smart Transformer (ST) has been proposed for increasing the hosting capacity of renewable energy sources in the power system with advanced control and communication capability. Its capability to connect-and disconnect itself from the main grid and to provide power from the Low Voltage (LV) grid to the Medium Voltage (MV) grid in the grid forming mode are an opportunity to realize an islanded operation mode. This operation mode requires a suitable controller design, which is forming the MV grid and the LV grid at the same time. This work proposes a modular ST architecture consisting of a three phase Cascaded H-Bridge (CHB) converter connected to Quadruple Active Bridge (QAB) converters. The design of the converter and its magnetic components is examined as well as the controller design for the QAB for the capability to address different operation modes. Grid forming operation on the both AC grid sides and the resulting constraints by means of active power availability are examined as well as opportunities to influence the power consumption of the grids. An experimental setup is presented and selected operation modes are demonstrated.