Vienna Rectifier with Gallium Nitride
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As the technology on wide bandgap materials such as gallium-nitride (GaN) has advanced rapidly, commercial GaN power devices with satisfying performance are available now. It is widely-known that GaN-based switching devices have several advantages over traditional Si based switching devices, such as lower ON resistance, faster switching speed, better thermal conductivity, and smaller size. However, researchers have not yet fully explored and applied GaN devices in many important power conversion applications such as power rectifiers. The three-phase three-level three-switch Vienna rectifier has advantages of low input current harmonics, low blocking voltage stress on the power semiconductor devices, high power density, high efficiency, and high reliability, and is widely used in many power applications. It is a good candidate topology to demonstrate GaN applications. In this thesis, a three-phase three-level three-switch Vienna rectifier is designed utilizing GaN FETs. The advantages and challenges of utilizing GaN FETs in Vienna rectifiers are discussed. The topology and operation principles of the Vienna rectifier are carried out. The control of the Vienna rectifier is introduced based on two types of the current control strategies, the instantaneous current control and the direct power control. A simulation model is established and run in MATLAB/Simulink to verify theoretical analysis. To provide a comparative analysis of GaN FET and Si MOSFET based Vienna rectifiers, two prototypes are built with each type of the power devices on a similar scale. Experiment results and design experience of GaN FET based and Si MOSFET based Vienna rectifier systems are presented. Advantages and benefits of applying GaN FET devices in the Vienna rectifier are concluded based on simulation and experimental results. It proves the promising potentials of GaN power devices in Vienna rectifier applications.