Multi-frequency power routing for cascaded H-bridge inverters in smart transformer application

The smart transformer is a solid state transformer with advanced control functionalities that can efficiently manage a low-voltage micro-grid by also supporting the medium-voltage grid. Cascaded H-bridge (CHB) converters proved to be a suitable option to realize the MV stage of the smart transformer due to their modularity and multi-level output. Normally the power is equally split among the CHB cells, however, in order to delay failures of the system, certain cells can be unloaded if premature deterioration is detected. In this work, multi-frequency power transfer is used to control the power processed by the dc/dc converters that supply the dc link of the CHB. The potential is analyzed analytically and validated experimentally