Investigation of Passive Rectifier Circuits for ModularSolid State Transformer Applications

Solid state transformers have a major role to play in grid integration of renewables in smart grid networks. Unidirectional, step up solid state transformers are state of the art in wind energy systems and solar PV parks. Modular SST topologies have gained significant impetus in recent research. Many research works have focussed on resonant tank converter topologies for modular SST applications. However, passive rectifier part remained uninvestigated and hence only secondary side rectifier and associated HF transformer is investigated in this work. In this work, three rectifier configurations are considered. Steigerwald's constant is derived for each independently and it is proved that irrespective of rectifier configuration, ac equivalent resistance remains unchanged for similar voltage and power ratings. Thus design methodology remains unchanged. Simulation results are analysed and various losses are estimated for full load operation. High frequency transformer design for minimum footprint and loss minimization are discussed. Further, it is concluded that bridge rectifier configuration yields minimum power losses.