LB
L. Bolzonella
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3 records found
1
Medium-Frequency Transformer for SST Applications
Design and Optimization
Journal article
(2026)
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Reza Mirzadarani, Leonardo Bolzonella, Zhengzhao Li, Zian Qin, Peter Vaessen, Pavol Bauer, Mohamad Ghaffarian Niasar
This work presents a downscaled validation of a medium-voltage, medium-frequency transformer (MFT) concept designed for high-current operation on the secondary side using multiple parallel paths. The design is based on a modular winding approach, which simplifies the construction process and conductor placement on the bobbin. A systematic design and optimization procedure is developed, combining analytical calculations and finite-element simulations to explore the mass-efficiency tradeoff and to select a candidate design that meets specified leakage inductance and loss targets. The developed prototype serves as a proof of concept, demonstrating that the electrical, magnetic, and insulation requirements of the full-scale MFT can be effectively verified at reduced power levels. The fabricated prototype is tested under short-circuit and partial discharge conditions. The impedance measurements confirmed the expected resonance behavior, and the partial discharge test results verified sufficient insulation performance under high-voltage stress. The results provide experimental evidence for the scalability and feasibility of the proposed transformer design and offer guidelines for the use of 3D-printed supports, grain-oriented electrical steel cores, and windings in medium-voltage, MFT systems for hydrogen production applications.
...
This work presents a downscaled validation of a medium-voltage, medium-frequency transformer (MFT) concept designed for high-current operation on the secondary side using multiple parallel paths. The design is based on a modular winding approach, which simplifies the construction process and conductor placement on the bobbin. A systematic design and optimization procedure is developed, combining analytical calculations and finite-element simulations to explore the mass-efficiency tradeoff and to select a candidate design that meets specified leakage inductance and loss targets. The developed prototype serves as a proof of concept, demonstrating that the electrical, magnetic, and insulation requirements of the full-scale MFT can be effectively verified at reduced power levels. The fabricated prototype is tested under short-circuit and partial discharge conditions. The impedance measurements confirmed the expected resonance behavior, and the partial discharge test results verified sufficient insulation performance under high-voltage stress. The results provide experimental evidence for the scalability and feasibility of the proposed transformer design and offer guidelines for the use of 3D-printed supports, grain-oriented electrical steel cores, and windings in medium-voltage, MFT systems for hydrogen production applications.
Conference paper
(2026)
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L. Bolzonella, F.A. Muñoz Muñoz, Mohamed Agazar, Johann Meisner, M. Ghaffarian Niasar
Very Fast Transients (VFTs) are high-frequency, steep-fronted voltage impulses that occur in high-voltage power systems and advanced power electronic applications. VFTs possess short rise times down to a few nanoseconds and peak voltages up to hundred kilovolts, they can cause potential degradation and failure in system insulation, equipment, and measurement technology. High frequency ranges (above 300 MHz) and amplitudes render accurate measurements of voltage transients challenging, and existing literature lacks in standardization and traceability. VTT Technical Research Center of Finland developed a resistive divider designed for capturing puncture test waveforms with amplitudes of 600 kV and 5 ns rise time. In this paper, the divider is evaluated for rise time measurements of pulsed waveforms with rise times below 5 ns, identifying the effect of measurement environment and parasitics, and optimizing the design to improve the performance. After the analysis, the modified design is capable of measuring pulses with rise times as fast as 1 ns with an estimated voltage rating of 300 kV. Thermal management considerations are also performed to ensure the resistive components can withstand the pulsed energy losses.
...
Very Fast Transients (VFTs) are high-frequency, steep-fronted voltage impulses that occur in high-voltage power systems and advanced power electronic applications. VFTs possess short rise times down to a few nanoseconds and peak voltages up to hundred kilovolts, they can cause potential degradation and failure in system insulation, equipment, and measurement technology. High frequency ranges (above 300 MHz) and amplitudes render accurate measurements of voltage transients challenging, and existing literature lacks in standardization and traceability. VTT Technical Research Center of Finland developed a resistive divider designed for capturing puncture test waveforms with amplitudes of 600 kV and 5 ns rise time. In this paper, the divider is evaluated for rise time measurements of pulsed waveforms with rise times below 5 ns, identifying the effect of measurement environment and parasitics, and optimizing the design to improve the performance. After the analysis, the modified design is capable of measuring pulses with rise times as fast as 1 ns with an estimated voltage rating of 300 kV. Thermal management considerations are also performed to ensure the resistive components can withstand the pulsed energy losses.
This paper presents the design and optimization of a Medium Frequency Transformer (MFT) for use in Solid State Transformer (SST) systems supporting green hydrogen production. Operating at 1 kHz and integrated within an LLC resonant converter, the transformer is optimized for minimal weight and high efficiency while ensuring adequate leakage inductance and insulation performance. A core-type configuration with cylindrical windings was selected based on FEM simulations and mass-efficiency trade-offs. The final prototype, using copper conductors, achieves 97.8% efficiency with a mass below 50 kg and meets the required 7 mH leakage inductance. High-voltage testing, including partial discharge and breakdown tests, confirmed the insulation coordination of the design. The results demonstrate a practical and scalable approach for high-performance SST integration in renewable energy applications.
...
This paper presents the design and optimization of a Medium Frequency Transformer (MFT) for use in Solid State Transformer (SST) systems supporting green hydrogen production. Operating at 1 kHz and integrated within an LLC resonant converter, the transformer is optimized for minimal weight and high efficiency while ensuring adequate leakage inductance and insulation performance. A core-type configuration with cylindrical windings was selected based on FEM simulations and mass-efficiency trade-offs. The final prototype, using copper conductors, achieves 97.8% efficiency with a mass below 50 kg and meets the required 7 mH leakage inductance. High-voltage testing, including partial discharge and breakdown tests, confirmed the insulation coordination of the design. The results demonstrate a practical and scalable approach for high-performance SST integration in renewable energy applications.