Comparison of Per-unit Models of Phase-shifted Full-bridge Converter

Advanced dc-dc converters such as phase-shifted full-bridge (PSFB) converters are employed in a wide range of applications owing to the features of fixed frequency operation and soft-switching for the devices. The converter design entails selecting many design parameters, resulting in multiple design choices for the same set of specifications. This necessitates a normalised comparison of the designs to analyse the performance indices. This paper studies and compares the per-unit models of the PSFB converter obtained using three established methods. Firstly, a large signal-based state space model of the converter considering the circuit non-idealities is presented. This is employed for developing the per-unit model of the PSFB converter using three models viz, state-plane normalization model, normalised large signal model and similarity transformation model. A study on the feasibility of the developed per-unit models and subsequent comparison is presented next. Next, the normalised designs of Si-based and SiC-based PSFB converters for a $1 kW, 400 V$ to $48 V$ system are compared. Finally, using the change of bases, a SiC-based converter for the aforementioned ratings is built and tested to verify the specifications.