Three Phase Bidirectional AC-DC Converter with 9-Switch Front-end Stage and Bipolar Voltage Fed Resonant Stages

Technology Overview: 

Three phase AC-DC converters play a crucial role when the electric power is consumed in the DC form. With the advent of Energy Storage (ES) applications, Electric Vehicles (EVs) and More Electric Aircrafts (MEA), the demand for high power density (>30W/in³) and high efficiency (>95%) for compact AC-DC converters with the power rating of more than 20kW is increasing. This invention describes two topologies of a novel three-phase AC-DC isolated converter, based on a front end nine-switch converter and two different rectifier topologies. In a conventional configuration, the first variation requires 18 switches whereas this technology only needs 15 semiconductors resulting in a compact converter with less cost. The conventional implementation of a second variation needs 24 semiconductors whereas our invention uses 21 switches. Hence, this converter reduces the device count and needs more compact cooling, reducing both the size and cost. Moreover, the switches in this converter are soft switched, allowing higher switching frequencies and hence can use low volume magnetic components and capacitors. The novel component connections in addition to the innovative modulation strategy reduce the stress on the capacitors enabling the stability and long life for the converter. 

Advantages: 

• Highly efficient operation.
• Absence of DC voltage in resonant capacitors leads to stable operation and longer lifetime of the converter.
• Soft-switching of semiconductor devices enabling high switching frequency high efficiency operation when implemented by SiC MOSFET (1200V rated). These are instrumental in achieving high power density, high efficiency and provide on-board galvanic isolation.
• Integrated front end reduces cost compared to conventional converters.