• wide-bandgap materials
• power electronics
• wbg
• three-phase rectifier
• rectifier
• fast charging
• electric vehicle

Electric mobility is becoming more relevant every year and the number of Electric Vehicles (EVs) worldwide is rapidly increasing. The main issue that still prevents EVs to become the main asset on the market is their poor autonomy, making it necessary to develop and install proper infrastructures to enable a fast charge of the EV battery in few minutes: the Fast Chargers.
A Fast Charger requires a power transfer to the vehicle up to 350 kW, therefore a modular approach, that relies on smaller building blocks operating in parallel, is commonly exploited to reach the total power specification. The energy transfer from the local power grid to the EV battery is realized by means of two modules: a three-phase boost rectifier and a DC-DC Buck converter.
New technology options based on wide-bandgap materials have been recently proposed in order to push device performance beyond the physical limits of standard silicon power devices. The two material candidates to replace and/or to complement silicon in power electronics applications are the Gallium Nitride (GaN) and the Silicon Carbide (SiC), and many power transistors (for both GaN and SiC) and power diodes (only SiC) are already available in the market.
In this thesis a single module of a three-phase rectifier is designed and simulated in order to compare the performance improvements that can be achieved in such an ac-dc converter realized with new GaN HEMT with respect to the counterparts realized with SiC and Si power MOSFETs.
The first part of this work introduces preliminary concepts related to charging stations, their classification, topologies and standards.The advantages of modular approach as well as the need of an electric isolation, arealso discussed. Innovative WBG materials are discussed in order to clarify their potential over silicon.
A review of the most common three-phase Power Factor Correction (PFC) architectures is proposed, with particular focus on recently developed architectures. After an extensive comparison of the achievable performance with these topologies, also considering the peculiar characteristics of a FC module, the VIENNA architecture is selected.
The VIENNA circuit is then analysed and designed, the input current and output voltage ripple are studied, and a simple analog PFC control circuit is designed for the sake of the simulation. Three different devices are then selected for the comparison, one for each material, on the basis of their electrical characteristics (RdsON, QG and Coss).
Subsequently, the circuit realized with GaN transistor is simulated with different power loads and switching frequency to evaluate its performance. Then, for an output power of 20 kW, three converters realized with either GaN, SiC or Si devices are compared over a wide range of switching frequencies. Finally, three converters, designed to operate at the same level of efficiency condition, are compared based on component cost and size over the full converter, highlighting the advantages of the GaN option over the others.