Bidirectional-GaN-based Soft-switched Current Source Converters

• Applicant: Professor Dr. Marcelo Lobo Heldwein
• Subject Area: Electronic Semiconductors, Components and Circuits, Integrated Systems, Sensor Technology, Theoretical Electrical Engineering
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 546288721

A conventional three-phase AC-DC current source converter (CSC) requires six power semiconductors with bidirectional voltage-blocking capability. To satisfy these specifications, a commonly favored approach involves the anti-series connection of two discrete unidirectional turn-off components. However, this method has inherent drawbacks, including increased conduction losses, costs, and gate driver complexity. Consequently, CSC systems are usually considered less advantageous when contrasted with VSC systems. Recent advancements in the power semiconductor industry have introduced monolithic bidirectional GaN enhancement-mode field-effect transistor (e-FET) prototypes. These devices feature bidirectional voltage-blocking capability, can control current flow in both directions, and have an equivalent on-resistance of a single unidirectional device. These features make them well suited for CSC applications, shifting the balance between multi-stage VSC topologies and single-stage CSC topologies towards the latter. In a broader sense, the lower losses enabled by WBG devices, especially GaN, can make single-stage topologies more attractive due to lower complexity and smaller volume. This opens new windows of opportunity for reevaluation of previously proposed converters and the proposal of new high-efficiency, high-compact single-stage topologies. Thus, bidirectional GaN power devices are very attractive in this context. However, even for GaN power devices, a disruptive increase in switching frequency while maintaining high efficiency seems possible only when soft switching techniques are employed. This work proposes using soft-switching techniques to CSCs based on bidirectional GaN Devices, and the central hypothesis under research is that Soft-Switched Current Source Converters based on bidirectional GaN power switches can enable higher efficiency and power density in three-phase AC-DC applications. This project proposal tries to tackle the following research questions: - How do you properly use bidirectional GaN soft-switched devices in CSCs? - What is the impact of soft switching in bidirectional GaN devices? - Which topologies and modulation schemes present the highest potential for high efficiency and high power density when they benefit from bidirectional GaN switches? - What is the impact of using GaN devices in soft-switched CSCs on the design of EMC filters? The answers to these questions might open a new history chapter for current source converters, which highly motivates this project.

• DFG Programme: Priority Programmes
• Subproject of: SPP 2312: Energy Efficient Power Electronics "GaNius"
• Co-Investigator: Dr. Gean Jacques Maia de Sousa