Single-Phase Bidirectional Power Factor Correction Boost Converter - Performance Evaluation of Totem-Pole PFC Converter Using Wide Band Gap Devices: GaN-HEMT and SiC
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- Institutt for elkraftteknikk 
Abstract Several DC loads in data center and telecom industry are fed by power electronic rectifiers. The same rectifiers are used to charge a number of batteries which serve as a backup power source in case of power outage or failure of rectifiers. However, the stored energy in the backup batteries is not utilized efficiently due to reliable source of power from the mains. Therefore, the industry is demanding a highly efficient PFC converter with bidirectional power flow. Significant improvement has been observed in the performance of power converters since the existence of wide band gap (WBG) devices in the power electronics industry. WBG devices provide high breakdown voltage and high thermal conductivity which enable to produce a more efficient and higher power density converter. In this master thesis, a novel bidirectional PFC converter with totem pole topology is presented for energy storage application. The totem pole topology employs two fast WBG switches and another two slow but very low on-resistance Si MOSFET switches. Since the current is not flowing through the body diode of power MOSFETs the reverse recovery dissipation of the active switches are significantly reduced. The proposed topology provides high PF with minimum input current harmonics, high efficiency and high power density. A literature review on wide band gap devices such as SiC and GaN has been done. The dual benefits of low on-resistance and reverse recovery charge from GaN enhance the performance of the totem pole topology, especially in terms of efficiency. Whereas, high thermal conductivity property of SiC enable to down size the heat sink and hence increase power density. A brief study is made on the functionality of the proposed converter for smart grid application together with battery capacities in telecom network. The research indicates that there is a huge potential of stored energy in the telecom site. Therefore, bidirectional PFC boost converter will be a power solution for efficient and cost effective use of electricity storage that also can feed power back to the grid. The proposed topology has been studied using computer simulation and tested in laboratory experiment. Based on the specification, a prototype is produced by employing SiC MOSFETs.