Grid-Forming Solid-State Transformers and the Virtual Synchronous

The distinction between grid-following and grid-forming control modes is the most important emerging concept in inverter-based-resource (IBR) integration on the modern power grid. Conventional renewable inverters and most pre-2024 SST products operate in grid-following mode: they detect the existing grid voltage and frequency and synchronize their output to it. Grid-forming mode is the opposite — the IBR establishes voltage and frequency references that other resources synchronize to, in the same way a conventional synchronous generator establishes the grid reference at every active power plant.

The virtual synchronous machine (VSM) control strategy is the most widely studied grid-forming approach. The VSM control software mimics the dynamic behavior of a conventional synchronous generator through a digital implementation of the swing equation — the differential equation that governs how a synchronous generator’s rotor angle and angular velocity respond to power-system disturbances. The VSM control gives an IBR the inertial response, damping, and short-term overload characteristics of a conventional generator, without the rotating mass.

For SST applications, the VSM strategy is implemented in the converter control software. The SST’s input AC-DC converter stage can be controlled to present the upstream grid with the same dynamic behavior a conventional synchronous machine would present. The downstream DC bus and the output DC-AC stage can independently support local loads under grid-forming control, creating an islandable microgrid that maintains stable voltage and frequency even when the upstream grid connection is lost.

The commercial application case is most acute in microgrids and in weak-grid renewable interconnects. A distribution feeder with high penetration of distributed PV becomes harder to stabilize as the fraction of grid-following inverters increases. Adding grid-forming SSTs at strategic feeder locations restores the local voltage and frequency anchoring that the displaced synchronous generation provided. The Independent Electricity System Operator (IESO) in Ontario, the Electric Reliability Council of Texas (ERCOT), and the California Independent System Operator (CAISO) have all expressed interest in grid-forming IBR specifications that SST products can implement.

The technical maturity question for grid-forming SST control is whether it is robust against the specific disturbance modes seen on production grids. Laboratory and hardware-in-loop testing using PSCAD and the Real-Time Digital Simulator (RTDS) platforms has been substantial. Field deployment of grid-forming SST products at distribution scale is in early stages. By 2027, several utility-class grid-forming SST products are expected to ship with VSM control as a standard option rather than a research feature.

Why It Matters

The emergence of grid-forming solid-state transformers (SSTs) and the virtual synchronous machine (VSM) control strategy has significant implications for the modern power grid. As the fraction of inverter-based resources (IBRs) increases, grid stability and reliability become major concerns. The VSM control strategy, which mimics the dynamic behavior of conventional synchronous generators, can help address these concerns by providing inertial response, damping, and short-term overload characteristics. The commercial application of grid-forming SSTs is particularly relevant in microgrids and weak-grid renewable interconnects, where high penetration of distributed PV can destabilize the grid. Utilities and grid operators, such as the Independent Electricity System Operator (IESO), Electric Reliability Council of Texas (ERCOT), and California Independent System Operator (CAISO), are taking notice of the potential benefits of grid-forming IBR specifications. As the energy landscape continues to evolve, with growing demand from data centers and increasing adoption of battery energy storage systems (BESS), the development of grid-forming SSTs with VSM control will play a crucial role in ensuring grid stability and reliability. With several utility-class grid-forming SST products expected to ship with VSM control as a standard option by 2027, the future of the grid is likely to be shaped by this emerging technology.

Critical Perspective

Editorial correction: This post is part of MGRID’s Solid-State Transformer industry coverage. As of May 2026, that body of work systematically framed manufacturer announcements, funding rounds, and laboratory demonstrations as commercial deployments. The reality is that field-deployed commercial-class SST in revenue service globally is measured in single digits, and almost every product cited in this series is at “announced” or “funded” stage, not “operational.” Readers should treat the specific claims in this post against the standards documented in our SST Industry Reality Check (the per-claim audit table maps marketing language to verifiable deployment status). The corrective article is the canonical reference for SST industry reality; this post remains published with its original framing so the editorial drift is traceable.

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