Abstract
This paper presents the design, development, and experimental validation of a 3/2-level Dual Active Bridge (DAB) converter utilising Silicon Carbide (SiC) devices for Solid-state Transformer (SST) applications.
The proposed converter architecture leverages a High-Frequency (HF) transformer to achieve superior system-level power density and efficiency, making it a promising candidate for next-generation power conversion systems. The design utilises Zero Voltage Switching (ZVS) zone to benefit from reduced switching losses.
Key contributions include the development of a 50kHz transformer with amorphous metal cores, the implementation of a planar busbars to mitigate stray inductance effects and test rig design. Experimental results demonstrate the converter’s operation at 50kHz, achieving an efficiency of 95% at 15kW output power.
This research advances the state-of-the-art in SST technology by proposing the 3/2-Level DAB as the ‘heart’ of future SSTs, offering a high-performance, compact, and flexible solution for modern power systems.
What is the technical breakthrough identified in the paper?
This project developed a high-efficiency, 100kW-capable power electronics converter that significantly reduces the size of traditional transformers. The high-frequency transformer used is approximately 1,000 times smaller than conventional 50Hz transformers typically found on electricity poles.
The design of a single cell of a future Solid-State Transformer (SST) using a 3/2 Level Dual Active Bridge architecture employs a Three-Level Neutral Point Clamped (NPC) converter on the primary side of the transformer, so can handle 1.2kV input voltage efficiently. The result is a system that:
- Can connect directly to the medium-voltage grid (11kV) with reduced number of cells required
- Achieves 95% efficiency in power conversion
- Creates compact, scalable, and efficient SST systems for modern energy infrastructure
How will this research help accelerate the development of converters for SST applications?
SSTs are the “smart transformers” of the future grid. This research addresses two big challenges in SST development:
High-voltage handling: the proposed converter can safely manage medium-voltage levels (e.g., 11kV) using fewer cascaded units, reducing system-level complexity.
Renewable integration: its compact and efficient design makes it ideal for solar and wind energy systems.
This work bridges the gap between current 1.2kV devices and emerging 3.3kV semiconductors, offering flexibility for future applications.
During experiments, the Catapult team also proved the operation at 15 kW (enough to power several homes), with a clear path to scale up to 100 kW, which will speed up adoption.
This research also addresses market limitations in available high-voltage semiconductor. This work shows that by utilising standard 1.2kV rated devices in a three-level topology, the system achieves safe and flexible higher voltages, offering a scalable solution for future power infrastructure.
And CSA Catapult’s recent report on SSTs highlights the huge opportunity they present. Even though SSTs are still a nascent technology, the market is projected to grow at a double-digit compound annual growth rate (CAGR) through to 2030.
The total global investment in power grid technology was projected to peak at nearly $400 billion in 2024, whilst global spending on renewables hit a record $735 billion in 2023.
What was CSA Catapult’s role in this research?
CSA Catapult led the design, development, and testing of the new SST cell which involved:
- In-house development of the 50kHz high-frequency transformer, validated through thermal and magnetic simulations and experimental testing
- Integration of state-of-the-art 1.2kV silicon carbide (SiC) devices, which offer much more efficiency than traditional silicon-based components
- System-level testing to validate the converter’s performance at 15kW, with a clear roadmap to scale up to 100kW for real-world deployment
How will this technology benefit our customers?
With this development, CSA Catapult has enhanced and validated its power electronics converter design and development capabilities.
Traditional low-frequency transformers are either too bulky or heavy. This design offers the following benefits:
- Compact and lightweight: easier to install in space-constrained environments
- Versatile: compatible with renewable energy systems, industrial applications, and smart grid infrastructure
- Efficient and scalable: reduces energy losses and supports high-power applications with fewer components when compared with a standard 2 Level converter-based solution
By validating this technology, CSA Catapult has enhanced its ability to deliver cutting-edge power electronics solutions tailored to customer needs.
What applications will this technology help deliver?
The proposed cell is designed to achieve modularity, to allow direct connection with the medium voltage grid (11kV), which can potentially enable super-fast, electric vehicle (EV) charging. Unlike current chargers limited to an output voltage of 400V, this technology supports higher output voltages (tested at 600V but can be increased to 800V), to meet the requirements of ultra and super-fast or fleet EV charging.
Beyond EVs, this research supports other high-impact applications including:
- Smart grids: enables intelligent energy routing and integration of renewables.
- Data centres: reduces energy consumption and physical footprint of power systems
Usman will chair the converter modelling, simulation and design session at ECCE Europe on Monday 1st September at 16:30, where he will discuss challenges and opportunities in converter modelling, simulation and design, and how semiconductors, and compound semiconductors can offer energy-efficient solutions to deliver next-generation power electronics applications.
Click here to learn more about the conference and papers.
