Photovoltaic String Inverters and Solid-State Transformers Are Convergent Architectures From Different Starting Points

Photovoltaic (PV) string inverters and solid-state transformers (SSTs) approach the same fundamental engineering problem — converting between an AC source and a DC load with active power-electronics control — from different starting points. The PV inverter industry developed from the residential and commercial solar markets, scaling up to multi-megawatt utility-scale inverters over the 2010s. The SST industry developed from the medium-voltage distribution market, scaling up from kilowatt-class research prototypes toward multi-megawatt commercial products. The two architectures are now converging at the multi-megawatt utility-scale frontier where the design choices increasingly look similar.

The technical comparison highlights both the similarity and the remaining distinctions. PV string inverters at the 100 to 350 kilowatt rating typically operate on a 1,500 volt DC string input, with three-phase AC output at 480 volts. SSTs at the equivalent power rating operate on a medium-voltage AC input (4 to 13.8 kilovolts) with either AC or DC output. Both architectures use silicon carbide MOSFETs as the dominant switching device, both use medium-frequency or high-frequency conversion stages to minimize magnetic component mass, and both have grid-forming control variants emerging.

The competitive consequence is direct: PV-inverter manufacturers are credible SST market entrants and vice versa. SolarEdge’s November 2025 partnership with Infineon for a 2-to-5 megawatt SST is the most visible example of a PV-inverter manufacturer extending into the SST market. Enphase’s 2026 IQ SST entry leverages residential-microinverter GaN expertise. SMA Solar Technology, Sungrow, and Huawei each have credible SST entry capabilities through their PV-inverter heritage even if they have not yet announced products.

The reverse direction — SST manufacturers extending into PV-inverter markets — is less visible commercially but technically straightforward. ABB and Hitachi Energy both have established PV-inverter product lines that predate their SST product roadmaps. Eaton has historically been less active in utility-scale PV-inverter markets but the Resilient Power acquisition brings PV-relevant capabilities. The architectural convergence means the competitive structure of both industries will increasingly merge through 2028 and beyond.

The strategic implication is that investors and procurement teams treating SST and PV-inverter as separate market segments are using a category framework that the industry itself is rapidly dissolving. By 2028 the dominant commercial vocabulary may be “power-electronics-based medium-voltage-grid-interface equipment” rather than the SST and PV-inverter labels currently in use. The underlying technology and manufacturing assets that produce both product categories are increasingly the same; the differentiation has migrated to control software, application-specific configuration, and customer-relationship management rather than to fundamental architecture.

Why It Matters

For manufacturers, PV string inverters and SSTs are converging on the same AC-DC power-conversion problem from opposite ends, which means solar-inverter makers with volume manufacturing could enter the SST market faster than the medium-voltage incumbents expect. That convergence is a competitive warning: the SST field may be reshaped by companies that already ship millions of inverters, not just by dedicated SST startups.

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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