Title: Solid-State Transformer Applications – A Glimpse Into the Future
Smart and/or Solid-State Transformers (SSTs) are power electronics interfaces between medium voltage and low-voltage AC or DC grids and are employing medium-frequency transformers for providing galvanic isolation and voltage scaling. Accordingly, SSTs show a high power density and are offering excellent controllability of the active and reactive power flow and/or voltage and current level and shape, as well as active protection features.
Early SST concepts date back to the 1970s, where research was mainly driven by the aim to reduce volume and weight of rail vehicles’ isolated AC/DC input stages. Later, possible applications in the context of Smart Grids shifted into focus, where the main drivers were enhanced power routing functionalities of power electronic systems compared to passive low-frequency transformers. This talk will first will first review current Megatrends, such as Clean Energy, Digitalization, Urbanization/Smart Cities, Sustainable Mobility, etc. and identify corresponding future applications for SST systems, especially in the context of DC microgrids and DC power distribution applications in datacenters, larger EV charging facilities, DC collector grids of off-shore wind parks, and future hybrid propulsion aircraft. Next, the talk covers key power converter topologies for the realization of SST systems which includes basic isolated DC/DC converter topologies, multi-cell converter structures with input-series / output-parallel (ISOP) configuration to achieve modularity and high reliability through redundancy, and structural options for realizing three-phase connectivity, as well as hybrid transformers. First industrial SST prototype systems are discussed to illustrate the practical applicability of the concepts. Finally, examples of current research activities on SST systems at ETH Zurich will be presented, including a highly compact/efficient 10kV-SiC-MOSFET-based converter module for future datacenter or ultra-fast EV charging applications.