Against the backdrop of rapid advancements in smart grids and renewable energy, solid-state transformers (SSTs), as next-generation power electronic devices poised to replace conventional line-frequency transformers, are increasingly being deployed in applications such as smart substations, renewable‑energy grid integration, microgrids, and high‑voltage, high‑frequency power conversion. Compared with traditional transformers, SSTs not only provide voltage transformation and electrical isolation but also offer multifunctional capabilities—including power factor correction, voltage regulation, reactive power compensation, power quality control, and hybrid AC/DC output—making them a cornerstone for building the future smart energy network.

SST topologies are categorized into single-stage and multi-stage configurations. Among these, the multi-stage SST—comprising a high-voltage AC‑DC stage, a high-frequency DC‑DC stage, and a low-voltage DC‑AC stage—has become the dominant architecture due to its superior flexibility in power management. In multi-stage SSTs, the high-frequency isolated DC‑DC conversion stage places stringent demands on the switching speed, voltage rating, and loss characteristics of power devices; owing to its material‑property advantages, the SiC MOSFET has emerged as the inevitable choice for this critical stage.

I. The Three Core Advantages of SiC MOSFETs in SSTs

Compared with conventional silicon-based IGBTs, SiC MOSFETs demonstrate irreplaceable technical advantages in SST applications:

Low On-Resistance Under High Voltage: In high-voltage busbar systems above 700 V, SiC MOSFETs maintain an exceptionally low on-resistance (Rds(on)), significantly reducing conduction losses, whereas silicon-based devices experience a sharp increase in on-resistance at high voltages.

Ultra-fast switching speed: Supports high-frequency operation from 20 kHz to over 100 kHz, far exceeding the typical range of conventional IGBTs (usually below 20 kHz), enabling a substantial reduction in the size of high-frequency transformers (HFTs) and a significant increase in overall power density.

Excellent body-diode reverse-recovery characteristics: zero reverse-recovery charge (Qrr ≈ 0), which significantly reduces switching losses and EMI noise in topologies such as LLC resonant converters and phase-shift full-bridge converters that rely on the body diode for freewheeling.

Key conclusion: For a single-stage SST, the DC–DC high-frequency conversion stage must employ SiC MOSFETs; the AC–DC rectification stage can adopt a hybrid solution using both SiC and IGBTs, with an all-SiC configuration recommended when higher efficiency is desired.

II. Decomposition of the SST Multi-Tier Architecture and Modular Design

Transformation level	Function Description	Recommended Device Platform
Level 1: High-Voltage AC-DC (Rectification Stage)	High-voltage grid connection (10 kV/35 kV) enables sinusoidal current on the grid side and power factor correction (PFC) at unity power factor, while stabilizing the high-voltage DC bus voltage.	1200V / 1700V SiC MOSFET (for high-efficiency applications); or a hybrid solution combining SiC MOSFETs with IGBTs.
Level 2: High-Frequency DC-DC Converter (Isolation Stage)	Achieving electrical isolation, voltage matching, and power regulation via a high-frequency transformer (HFT) is the core function of an SST for voltage conversion and energy management, operating at frequencies of 20 kHz to over 100 kHz.	1200V / 1700V / 3300V SiC MOSFET (Essential Choice)
Level 3: Low-Voltage DC-AC (Inverter Stage)	Convert the low-voltage DC bus to a stable power-frequency AC voltage, supplying it to electrical loads or microgrid ports.	1200V / 1700V SiC MOSFET

III. System Architecture Overview

High‑voltage grid connection (10 kV/35 kV) → Stage 1: High‑voltage AC‑DC rectification (1200 V/1700 V SiC MOSFETs) → High‑voltage DC bus (HVDC) → Stage 2: High‑frequency DC‑DC isolated conversion (1200 V/1700 V/3300 V SiC MOSFETs + high‑frequency transformer HFT) → Low‑voltage DC bus (LVDC) → Stage 3: Low‑voltage DC‑AC inversion (1200 V/1700 V SiC MOSFETs) → Line‑frequency AC output (for electrical loads/microgrid)

Summary of Core Values:

Higher frequency: Supports high-frequency operation from 20 kHz to over 100 kHz, significantly reducing transformer size.

Higher efficiency: Extremely low switching and conduction losses, significantly reducing system temperature rise.

Higher Voltage Rating: The 3,300 V platform is compatible with direct‑connection applications at 10 kV and 35 kV.

Higher Integration: TO-247-4 unified package, simplifying modular design.

Solution Topology

Model Recommendations

No.	Part No.	VDSS (V)	Type	ID(A)		VGSS-OP (V)	VGS-TH (V)			RDS(ON)(TJ=25℃)		RDS(ON)(TJ=175℃)		Package	Product
No.	Part No.	VDSS (V)	Type	TC=25℃	TC=100℃	VGSS-OP (V)	Min	Type	Max	Type (mΩ)	Max (mΩ)	Type (mΩ)	Max (mΩ)	Package	Product
1	GAC170N015F4EB	1700	N	153	108	-5/18	2	2.9	4	15	21	27	-	TO-247-4	SiC MOSFET
2	GYC170N019F3BB	1700	N	132	84	-5/20	2	2.75	4	19	28	46	-	TO-247-3	SiC MOSFET
3	GYC170N019F4BB	1700	N	132	84	-5/20	2	2.8	4	19	26	26	-	TO-247-4	SiC MOSFET
4	GYC170N045F3BB	1700	N	67	45	-5/20	2	2.8	4	45	70	78	-	TO-247-3	SiC MOSFET
5	GYC170N045F4BB	1700	N	67	45	-5/20	2	2.8	4	45	70	78	-	TO-247-4	SiC MOSFET
6	GYC170N075F3BB	1700	N	33	29	-5/20	2	2.9	4	75	95	186	-	TO-247-3	SiC MOSFET
7	GYC170N075F4BB	1700	N	33	29	-5/20	2	2.5	4	75	95	105	-	TO-247-4	SiC MOSFET

Model Recommendations

No.	Part No.	VDSS (V)	Type	ID(A)		Vth			RDS(ON) TJ= 25℃		Package	Product
No.	Part No.	VDSS (V)	Type	TC=25℃	TC=100℃	Min	Type	Max	Type (mΩ)	Max(mΩ)	Package	Product
1	GDS060J120F3EC	600	N	26	16.5	2.5	3.5	4.5	108	120	TO-247-3	SJ MOSFET
2	GDS060R090F3EC	600	N	31	20	3	4	5	86	99	TO-247-3	SJ MOSFET
3	GDS060R070F3EC	600	N	44	27.7	3	4	5	63	70	TO-247-3	SJ MOSFET
4	GDS060R038F3EC	600	N	52	32.8	3	4	5	34	38	TO-247-3	SJ MOSFET
5	GDS060R022F3EC	600	N	110	69.5	3	4	5	21	22	TO-247-3	SJ MOSFET