The global energy transition is deeply integrated with the digital economy, driving power systems to upgrade toward higher efficiency, intelligence and flexibility. As core equipment for power transmission and conversion, technological innovation of transformers has become a linchpin for high-quality industrial development.

Conventional transformers support grid operation based on electromagnetic induction principles. However, against emerging demands including renewable energy grid integration, booming AI computing power and smart grid construction, their inherent drawbacks—bulky footprint, inflexible performance and single functionality—have become increasingly prominent.

Solid-State Transformer (SST) delivers disruptive upgrades enabled by next-generation power semiconductor technology, emerging as core equipment bridging new power systems and diverse end loads. Research data from authoritative institutions such as GGII (Gaogong Industry Research Institute) indicates the global SST market size reached approximately USD 1.5 billion in 2025, with a projected climb to USD 12 billion by 2030, representing a Compound Annual Growth Rate (CAGR) exceeding 35% between 2025 and 2030. China leads global market growth: its domestic SST market hit CNY 4.2 billion in 2025, growing 38.2% year-on-year. CCID Consulting forecasts China’s SST market will sustain a CAGR above 40% from 2025 to 2030, surpassing CNY 35 billion by 2030 to become the world’s largest standalone SST consumption market.

Powered by cutting-edge power semiconductors, SST delivers revolutionary upgrades and serves as critical interconnection hardware for new power systems and diversified terminal loads. GiantMag Intelligent focuses on magnetoelectric sensing and control chips, closely tracking frontier advancements in the power industry. This article analyzes the current landscape and trends of the SST industry across four dimensions: technical comparison, industrial chain, application scenarios and domestic enterprise layout, providing references for industrial stakeholders while highlighting the core value of GiantMag Intelligent.

I. The Last Hundred Meters: Iteration Competition Between Legacy and Solid-State Transformers

At the "last hundred meters" of power grids—from distribution rooms to server racks, energy storage containers to charging piles—conventional transformers face unprecedented challenges. Their bulky size and rigid performance occupy costly urban real estate, and they fail to cope with rapidly fluctuating loads from AI computing infrastructure. The booming adoption of SST is reshaping this landscape.

Also named power electronic transformers, SST is an innovative power conversion device built on advanced power electronics, high-frequency conversion and intelligent control technologies. Its core functions cover voltage level transformation, bidirectional energy flow and power quality regulation. Compared with conventional transformers, SST represents a technological revolution that replaces passive electromagnetic induction with active power semiconductor switching. To fully grasp the value of SST, we first clarify core technical gaps against legacy transformers, objectively analyze their respective merits and demerits, and define the application boundaries and growth potential of SST.

1.1 Divergence in Core Operating Principles

1.2 Comprehensive Cross-Dimensional Performance Comparison

1.3 Merit Summary & Application Boundaries

Core strengths of SST: high energy efficiency, compact footprint, full-spectrum functionality, low operation & maintenance (O&M) burden and ultra-fast response, perfectly aligning with carbon peaking & carbon neutrality targets and new power system requirements. Its limitations include high upfront capital expenditure, steep technical barriers, severe thermal management challenges and immature standardization frameworks.

The two technologies do not serve as full substitutes. Conventional transformers retain cost advantages for large-scale power transmission scenarios, while SST is irreplaceable for emerging high-flexibility applications and will gradually become mainstream hardware for next-gen power infrastructure.

II. Analysis of Core SST Design Solutions & Topological Architectures

This chapter breaks down system design, mainstream topologies and core optimization links of SST, elaborating its underlying technical core.

2.1 Mainstream SST Topologies & Hierarchical Design

SST topologies are categorized into single-phase and three-phase variants based on voltage and power ratings. Three-phase architectures dominate medium/high-voltage high-power use cases such as power grids, renewable energy facilities and data centers, representing the primary focus of industrial R&D and commercialization today.

Input Stage Topology Design

For medium and high-voltage applications, the input stage mainly adopts Cascaded H-Bridge (CHB) and Modular Multilevel Converter (MMC) topologies:

1. Cascaded H-Bridge (CHB) Topology: Simple structure, high modularity and low control complexity. It is the mainstream commercial SST solution in China for 10kV distribution networks, enabling flexible voltage scaling via module cascading.

2. Modular Multilevel Converter (MMC) Topology: Delivers superior output waveform quality with minimal harmonic distortion, suited for 35kV and above high-voltage scenarios. It exhibits outstanding performance in ultra-high-voltage flexible HVDC transmission and large-scale renewable energy base grid integration, yet requires far more complex control algorithms.

Isolation Stage Topology Design

The isolation stage acts as the core of SST for high-frequency galvanic isolation and efficient energy transfer, and is the primary target for topological optimization. The industry predominantly adopts Dual Active Bridge (DAB) topology, alongside optimized resonant variants including Series Resonant Converter (SRC) and LLC resonant converter, selectable based on operational conditions.

Output Stage Topology Design

Two categories of output-stage topologies exist to match different load requirements:

1. Three-phase full-bridge inverter topology for AC loads: delivers stable grid-frequency AC output with integrated reactive power compensation and harmonic suppression capabilities.

2. DC/DC Buck-Boost topology for DC loads: generates steady DC voltage for data centers, DC fast chargers and energy storage systems, marking the fastest-growing product segment in current market demand.

2.2 Optimization of Core Isolation Stage Topology: DAB vs. SRC

Topology selection for the isolation stage directly determines overall SST efficiency, power density and operational stability. DAB and SRC represent the two most widely adopted mainstream architectures, with distinct core characteristics and efficiency gaps outlined below.

Dual Active Bridge (DAB) Topology

The classic isolation-stage solution for SST, DAB consists of full-bridge circuits on both primary and secondary sides coupled with a high-frequency transformer. It supports bidirectional energy flow with straightforward control logic and rapid dynamic response, ideal for use cases requiring two-way power exchange. Its key feature enables Zero-Voltage Switching (ZVS) across all power switches. However, switches turn off at peak current, generating substantial turn-off tail current losses—efficiency drops notably under light-load operating conditions.

Series Resonant Converter (SRC) Topology

SRC integrates a resonant cavity on the basis of DAB, realizing both Zero-Voltage Switching (ZVS) and Zero-Current Switching (ZCS) for power switches. It fundamentally eliminates turn-off losses and boosts overall equipment efficiency by 0.5%–1% compared with DAB under rated operating points for superior energy performance. Nevertheless, its resonant characteristics elevate peak current, increasing conduction losses; it demonstrates weaker adaptability to widely fluctuating load profiles versus DAB.

Comprehensive Evaluation

DAB topology is better suited for renewable energy and energy storage applications with bidirectional power flow and volatile load conditions. SRC topology fits data centers and ultra-fast charging stations featuring stable operating profiles and strict efficiency requirements. Hybrid topologies combining advantages of both architectures are emerging across the industry to optimize full-load-range SST efficiency.

2.3 SST Mechanical Structure & Fundamental Control Logic

2.3.1 Universal SST System Architecture

F. Wald et al., "Applications and Services of Solid-State Transformers in Active Distribution Networks—A Critical Review," in IEEE Transactions on Smart Grid, vol. 16, no. 5, pp. 3615-3637, Sept. 2025, doi: 10.1109/TSG.2025.3574007.

Consensus has not yet been reached within academia regarding the optimal circuit combination for grid-tied SST equipment. To clearly illustrate SST characteristics, the diagram above presents a versatile, fully functional representative three-stage power electronic converter architecture, enabling interconnection between medium-voltage (MV)/low-voltage (LV) AC and DC power grids.

Control logic for three-stage SST is split into three independent base controllers: MV-side AC/DC converter controller, DC/DC converter controller and LV-side converter controller. The universal SST control framework comprises two layers: the base controller layer and the auxiliary service control layer. Signals marked with an asterisk (*) denote reference setpoints instead of measured real-time values; red-highlighted signal nodes require dedicated sensing components for critical real-time measurement.

1) MV-Side Converter Control

As illustrated in the top-left block, the MV-side AC/DC converter adopts control strategies analogous to standard active front-end converters. Its core function leverages cascaded current and voltage control loops to regulate AC-side current i₁ and stabilize MV DC-link voltage vdc1 at its reference v*dc1. Measured grid voltage v₁ can be introduced post the current controller to build a feedforward control scheme for faster response.

Multiple topologies can be deployed for the MV-side converter, with MMC as the most prevalent. MMC demands complex modulation algorithms plus supplementary voltage balancing and common-mode compensation controllers to guarantee stable converter operation.

Additional auxiliary service control loops can be cascaded atop base regulation to assign new operating references for dq-axis currents. For instance, an oscillating active current component id can be superimposed onto the active current reference id output from the MV DC-link controller to implement harmonic suppression. Input signals for the MV service control module vary based on enabled grid services—voltage amplitude reference v*1 is required for voltage/VAr support functions.

Further service expansion enables advanced grid support capabilities, equipping both sides of the converter with Grid-Forming (GFM) control. Droop control logic for DC-link voltage can be embedded within the DC/DC converter to allocate DC voltage regulation responsibilities to converters on both interconnected grid sides. Energy support required for GFM control is realized via coordinated interaction with downstream LV grids; power flow control inside SST is achieved by utilizing active power flexibility of downstream loads derived from frequency and voltage deviation signals.

2) DC/DC Converter Control

Positioned in the upper-middle section of the diagram, the DC/DC conversion stage prioritizes stabilizing LV DC-link voltage while transmitting power from the MV DC bus to the LV DC bus. Taking DAB topology as an example, its core control principle relies on phase-shift regulation between primary and secondary voltages of the Medium-Frequency Transformer (MFT) to deliver controllable bidirectional power flow and generate target current magnitude and direction. This regulation logic is encapsulated in the central power flow controller block, which receives inputs of measured LV DC-link voltage and its reference v*dc2.

Underlying control and modulation techniques are flexibly configurable per specific topology and operating point, including linearized control, disturbance observer-based control and sliding-mode control. Advanced hardware-level switching algorithms such as Zero-Voltage Switching (ZVS) for DAB effectively improve conversion efficiency, extend device service life and reduce thermal stress on power switches. Sophisticated soft-switching power electronic switching schemes are increasingly adopted within current-source inverters and specialized complex converter topologies to maximize energy conversion efficiency.

3) LV-Side Converter Control

The LV-side DC/AC converter in the top-right block operates under two core modes determined by application scenarios: Grid-Forming (GFM) and Grid-Following (GFL). Per global industrial standards, GFM controllers must "maintain constant or near-constant internal voltage phasors across sub-transient to transient timeframes." Implementation methods include classic virtual synchronous machine controllers with dedicated voltage reference inputs, alongside emerging technologies such as dispatchable Virtual Clock Oscillators (VCOs) and advanced droop controllers.

Under GFL mode, the converter deploys current control schemes similar to the MV-side converter, exchanging active power, reactive power and harmonic power per LV AC grid demand. The LV grid control & service module in the bottom-right block accepts diverse feedback and reference signals tailored to target applications, such as target active power deviation (ΔP2), bilateral grid frequency deviations (Δf1, Δf2) and LV voltage deviation (v2).

2.3.2 Fundamental Control & Measurement Signals

Within the three-stage SST topology, voltage and current measurements support control requirements of the MV converter, DC/DC converter, LV converter and system-level coordination logic, detailed as follows:

1) Core Measured Voltage Signals

2) Core Measured Current Signals

III. Synergistic Industrial Chain Development & Massive Expansion of Application Scenarios

The SST industry follows a three-tier industrial chain layout: upstream components lay technical foundations, midstream equipment manufacturers hold core proprietary technologies, and downstream applications drive market demand. Maturing technology and falling costs have pushed SST deployments from pilot demonstrations to large-scale commercialization, triggering transformation across multiple vertical sectors and forming core infrastructure for new power system construction.

3.1 Core Industrial Chain Layout

Upstream Core Components

Power semiconductors constitute the highest-cost segment, accounting for approximately 32% of total SST bill of materials (BOM); SiC device share rises to 40%–50% for medium/high-voltage variants. IGBTs boast high domestic localization rates for medium/low-voltage applications, though high-voltage high-power modules remain partially import-dependent. Localization of SiC/GaN devices stands at roughly 25%, with projections of 50% domestic SiC MOSFET penetration and 30% cost reduction by 2026.

Domestic substitution of high-frequency magnetic materials (amorphous alloy, nanocrystalline alloy) accelerates, with manufacturers such as Haining Dongmag continuously expanding production capacity. Current and voltage sensors act as critical perception hardware for SST intelligent control and protection, integrated across all power conversion stages to deliver real-time data for closed-loop topological control, overcurrent/overvoltage protection and efficiency optimization—indispensable for high-precision, high-reliability SST operation. Domestic enterprises including GiantMag Intelligent have launched dedicated high-frequency current sensor products optimized for SST operating conditions. Chinese manufacturers have also achieved preliminary breakthroughs in localized supply of supporting hardware including intelligent control chips and thermal dissipation materials, steadily enhancing supply chain autonomy and controllability.

Midstream Equipment Manufacturing

Core technical barriers reside in topological design, high-frequency magnetic integration and intelligent control algorithms. Three enterprise categories compete in this segment: legacy power equipment leaders (Xi’an XD Electric, Sifang Automation), power semiconductor manufacturers expanding downstream production (StarSemiconductor) and emerging innovative tech firms (Kelong Electric). Competitive advantages center on R&D investment, production capacity and customer resource pipelines.

Downstream Application Scenarios

Market demand diversifies rapidly, with four core verticals: smart grids, renewable energy, AI data centers and electric vehicle charging. Future expansion will extend to frontier fields including space power supply and deep-sea exploration. Auxiliary sectors covering testing & certification and intelligent O&M services mature progressively to standardize industrial development.

3.2 Core Application Scenarios

As technology matures and costs decline, SST deployments transition from pilot projects to mass commercialization, currently concentrated in four primary verticals with upcoming penetration into space power, deep-sea exploration and distributed energy systems, unlocking expansive market demand.

1. Traction Power Supply

Limitations of conventional line-frequency traction transformers (16.7Hz standard across Europe):

• Account for 12%–18% of locomotive total weight, power density limited to 0.25–0.35 kVA/kg

• Space constraints induce excessive transformer current density, restricting overall efficiency to 89%–92%

SST Solution Advantages:

• 50% weight reduction, power density elevated to 0.5–0.75 kVA/kg

• 2%–4% overall efficiency improvement

2. Electric Vehicle Charging

Drawbacks of conventional DC fast-charging stations (line-frequency transformer + LV switchgear + charging piles):

• Excessive land footprint

• Fixed transformer capacity with zero scalability

• High current loss across LV AC-DC conversion stages, limiting grid-to-vehicle conversion efficiency below 95%

SST Solution Advantages:

• Modular architecture supporting flexible capacity expansion

• Eliminates line-frequency transformers and LV switchgear, cutting land occupation by 50%

• Higher efficiency AC-DC conversion delivering approximately 2% overall system efficiency gain

3. Data Center Power Supply

Pain points of traditional low-voltage AC-DC power distribution:

• Severe no-load losses on line-frequency transformers

• Large quantities of distributed power supply hardware occupy over 50% of total facility floor space (Case reference: 297 m² distribution zone housing 34 power devices from 4 vendors with 36 distinct communication interfaces)

• Low overall efficiency capped at 95%–95.5% due to LV AC-DC conversion bottlenecks

SST Solution Advantages:

• Modular design simplifies deployment and maintenance workflows

• High integration drastically reduces power hardware count, cutting distribution area footprint by 63%

• 2%–3% improvement in total system efficiency

Case reference: Xuji Electric’s 2.4MW SST for data center applications achieves peak efficiency of 98%.

4. Medium-Voltage AC Grid-Tied PV Systems

Disadvantages of legacy schemes (PV string inverter + line-frequency transformer):

• Continuous no-load transformer losses during off-peak nighttime hours

• Combined efficiency of 98.5% (inverter) × 98% (transformer) = total system efficiency limited to 96.5%

• Parallel operation of large inverter arrays prone to transient instability risks

SST Solution Advantages:

• Minimized no-load power loss

• High integration and superior power density

• 1% improvement in overall conversion efficiency

Case reference: TBEA’s 1MW SiC-based MV grid-tied PV SST reaches peak efficiency of 98%.

5. Renewable Energy Medium-Voltage DC Collection

Limitations of conventional AC collection architectures:

• Multiple power conversion stages and high current magnitude reduce overall efficiency

• Severe power loss across MV AC collection cables

• AC grids susceptible to power quality issues including harmonic distortion and resonance

SST DC Collection Architecture Advantages:

• Integrated power conversion stages paired with soft-switching technology to cut energy loss

• Low-loss MV DC cables boost aggregate collection efficiency

Case reference: ±30kV / 1MW PV DC step-up converter developed by the Institute of Electrical Engineering, Chinese Academy of Sciences (IEECAS).

6. AC/DC Hybrid Distribution Grids

Characteristics of AC/DC hybrid distribution networks:

• Compatible with existing AC grid infrastructure, enabling flexible interconnection of diverse renewable energy sources and novel loads

• Incorporates extensive AC/DC and DC/DC power conversion stages

Multi-Port SST Functional Capabilities:

• Integrated MV AC/MV DC and LV AC/LV DC connection ports

• Independently adjustable port voltages with bidirectional energy exchange between all terminals

• Reduced power conversion stages for elevated overall system efficiency

Case references: 3MW multi-port SST deployed in Tongli, Suzhou; multi-port AC/DC SST demonstration project in Dongguan.

7. DC Distribution Grids

DC distribution grid characteristics:

• Lower cable capital expenditure and higher transmission efficiency

• Optimized interconnection interface for renewable energy and energy storage systems

Core Role of SST (DC Transformer):

• The sole viable technical solution to implement voltage transformation and bidirectional energy exchange between MV DC and LV DC networks

Case References:

1. Wujiang MV/LV DC Distribution Demonstration Project: ±10kV / 750V 2MW SST

2. Hangzhou Dadongjiang DC Distribution Grid Demonstration Project: ±10kV / ±375V 500kW SST

Looking ahead, SST will penetrate cutting-edge aerospace power systems and deep-sea exploration equipment. Space environments impose stringent weight and size constraints incompatible with conventional transformers; compact, highly reliable SST delivers stable power supply for space stations and interplanetary exploration hardware, facilitating deep space exploration.

3.3 Industrial Transformation Value

Large-scale SST deployment accelerates the transformation of power systems toward coordinated source-grid-load-storage operation, enables renewable energy to become primary power generation sources, empowers digital economy and advanced manufacturing upgrades, and drives collaborative advancement across upstream and downstream industrial chains—forging a growth ecosystem featuring upstream technological breakthroughs, midstream industrial expansion and downstream demand explosion.

IV. Conclusion: SST Spearheads Energy Transformation, MAGTRON Delivers Critical Sensing Support

Leveraging high efficiency, compact form factor and intelligent controllability, Solid-State Transformers break through performance limitations of legacy transformers to become core hardware for new power systems, catalyzing industrial chain upgrades and enabling development across renewable energy, AI computing and transportation verticals. Stable, high-efficiency SST operation relies entirely on precise data input from core sensing hardware—current sensors act as the "precision vision system" of SST equipment.

As a National Specialized, Refined, Unique & Innovative "Little Giant" Enterprise, MAGTRON specializes in magnetoelectric sensing and chip control technologies. Our series of current sensors deliver ultra-high sensitivity, precision and microsecond-level response, accurately capturing high-frequency micro current fluctuations within SST hardware to supply precise data for equipment control, fault protection and efficiency optimization—perfectly matching SST high-frequency operating characteristics.

The energy conversion revolution has fully launched, marked by the gradual phase-out of conventional transformer limitations and widespread SST commercialization. Adhering to product quality principles of pragmatism, agility and innovation, MAGTRON aligns product development with evolving SST industry requirements. We collaborate with SST manufacturers to unlock new paradigms of efficient energy utilization, support high-quality development of China’s energy industry, and advance toward an intelligent, efficient and carbon-neutral energy future.