The growing use of converter-interfaced generation, energy storage, and large electric loads is creating new challenges for power-system stability, resilience, and expansion. Although solid-state transformers (SSTs) and medium-voltage DC technologies have advanced substantially, most research continues to treat them as individual devices rather than coordinated building blocks of future grid architecture.

This lecture traces a control-centered progression from grid-forming SSTs, through grid-forming control of multi-terminal MVDC networks, to SST-enabled multi-terminal MVDC systems. It first introduces Dual-Measurement Frequency Droop (DMFD), which enables grid-forming operation at both AC terminals of an SST. This allows multiple SST-connected systems to establish interconnected microgrids during upstream outages, regulate voltage and frequency, coordinate photovoltaic and battery resources, and maintain connected renewable generation without high-speed communications.

The same control principle is then extended to multi-terminal MVDC networks to coordinate grid-forming behavior across AC and DC terminals, improve disturbance sharing, and reduce dependence on fixed master-slave roles. The lecture concludes by introducing an emerging architecture in which the internal converters and DC buses of SSTs form meshed MVDC interconnections without additional converter stations.

Together, these developments could reposition SSTs from advanced transformer replacements to strategic grid infrastructure, enabling multi-path power delivery, graceful degradation and recovery, and a phased transition from legacy AC systems to resilient hybrid AC/DC networks. Data centers and other critical large loads provide a compelling application, particularly when strengthening the surrounding sub-transmission system is as important as protecting the load itself.