Three-Phase AC/DC Converter Topology for Low-THD High-Voltage Input

The converter is divided into multiple independent half-bridge modules (first, second, third, and fourth modules) with each module handling a specific phase and polarity combination. This segmentation allows the system to achieve low THD through controlled switching while using fewer components per module compared to a full Vienna rectifier, thus resolving the contradiction between current quality and device complexity.

The controller dynamically controls the switching of MOSFETs in each half-bridge module to achieve discontinuous conduction mode operation. By dynamically adjusting the switching timing and duty cycles, the system minimizes current distortion and maintains high power factor while using a simplified topology with fewer components than static rectifier designs.

The input voltage is divided and handled by multiple half-bridge modules operating in series. Each module uses standard voltage-rated MOSFETs that can be easily manufactured, rather than requiring expensive ultra-high voltage devices. The segmented architecture allows the system to process high input voltages while maintaining cost-effectiveness through the use of conventional components.

Flying capacitors are introduced as intermediary energy storage elements between the half-bridge modules. These capacitors facilitate voltage balancing and energy transfer, enabling the system to handle high input voltages through multiple lower-voltage stages rather than requiring single ultra-high voltage switches, thus reducing manufacturing cost.

The PFC rectifier function and DC/DC conversion function with galvanic isolation are merged into a single integrated converter stage. The half-bridge modules perform both rectification and voltage transformation simultaneously, eliminating the need for separate cascaded DC/DC converters and reducing the total number of switches while maintaining high input voltage capability and galvanic isolation.

Each half-bridge module is designed to perform multiple functions: PFC rectification, voltage step-up/step-down, and galvanic isolation through the flying capacitors. This multi-functionality allows a single converter stage to replace what would traditionally require multiple separate converters, thereby reducing device complexity and switch count while achieving high input voltage capability.

The design uses standard silicon-based MOSFETs with antiparallel diodes instead of expensive wide-band-gap devices like SiC. While silicon devices have higher conduction losses, the overall efficiency is maintained through optimized switching control and discontinuous conduction mode operation. This approach achieves acceptable efficiency at significantly lower device cost, making the converter more manufacturable.

The converter operates in discontinuous conduction mode with specific duty cycle ranges (0.2 to 0.8) to optimize the performance of standard silicon devices. By changing the operating parameters and switching strategy, the system compensates for the higher conduction losses of silicon MOSFETs, achieving efficient operation without requiring expensive wide-band-gap devices.