Synchronous Condensers Plus Grid-Forming Solid-State Transformers Are the Hybrid Plant Architecture for Inverter-Heavy Grids
- NREL SuperFACTS: synchronous condenser + grid-forming BESS under unified controller
- Synchronous condenser provides real inertia + reactive power; grid-forming SST provides active control + bidirectional flow
- Hybrid plant provides dispatchable real power + full ancillary services + fault current + system inertia from single installation
- Lister Drive UK project combines synchronous condenser with BESS for grid stability services
- ERCOT, CAISO, UK National Grid ESO procurement specs increasingly require capabilities pure-IBR plants cannot meet
The transition from synchronous-generation-dominant electrical grids to inverter-dominant grids has produced a structural problem: the system inertia, system strength, and fault-current capacity that conventional generators provided are reduced as inverter-based resources (IBRs) displace synchronous generation. Two architectural responses are emerging. The first is synchronous condensers — synchronous machines spinning without connection to a prime mover, providing inertia and reactive power without producing real power. The second is grid-forming solid-state transformers (SSTs) with virtual synchronous machine (VSM) control. Combining both technologies in a single hybrid plant has been the focus of recent NREL research.
NREL’s SuperFACTS architecture, documented in 2021-2022 research publications, combines a synchronous condenser with a grid-forming battery energy storage system in a single plant under a unified controller. The plant can provide dispatchable real-power output, full ancillary services (frequency response, voltage support, oscillation damping), fault-current contribution for protective relaying coordination, and system inertia all from a single integrated installation. Replacing the BESS in the SuperFACTS architecture with an SST plus BESS preserves all of these capabilities while adding the SST’s active power-quality control.
The use case for the synchronous-condenser-plus-SST hybrid is most acute on weak grid feeders, on transmission-distribution boundaries where grid-forming capability is required, and on island or microgrid installations where the synchronous condenser’s real inertia is needed but where the conventional engine-driven prime mover is unwanted. Several utility installations of synchronous condensers paired with grid-forming inverters or SSTs are in commissioning through 2024-2026, including the Lister Drive project in the United Kingdom which combined a synchronous condenser with a BESS to provide grid stability services.
The economic structure of the hybrid plant is also interesting. Ancillary services markets — frequency regulation, voltage support, oscillation damping, short-circuit-capacity provision — now reward operators for capabilities that conventional power plants used to provide as byproducts of real-power generation. A pure SST plus BESS plant can capture much of the ancillary-services revenue. Adding a synchronous condenser to the same plant captures additional revenue (specifically the system-inertia products that pure-inverter-based resources cannot provide) at the cost of additional capital.
The strategic implication for the SST industry is that the synchronous-condenser-plus-SST hybrid plant pattern is a real commercial opportunity adjacent to the standalone SST applications. The combined plant can address utility procurement specifications that pure-SST products cannot meet, particularly in jurisdictions like Texas (ERCOT), California (CAISO), and the UK (National Grid ESO) where the loss of synchronous generation has produced documented grid-stability concerns. SST manufacturers that develop integrated hybrid-plant product offerings, rather than standalone SST product lines, may capture more durable market position through 2028 and beyond.
Why It Matters
For system operators facing inverter-dominant grids, the loss of synchronous inertia and fault-current capacity is a structural reliability problem, and pairing synchronous condensers with grid-forming SSTs is one hybrid architecture being proposed to restore both. This matters as inverter-based resources displace conventional generators faster than replacement grid-strength mechanisms are deployed, leaving a widening gap that grid-forming hardware is meant to fill.
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](/?p=9044) (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.
Related Coverage
ERCOT, CAISO, UK National Grid ESO procurement specs increasingly require capabilities pure-IBR plants cannot meet
