A 100kHz 15kW Planar DAB Converter Transformer for Medium Voltage Solid State Transformer Applications

A 100kHz 15kW transformer with planar form factor is proposed for cascaded H-bridge solid state transformer (CHB-SST) applications. A novel winding and casting method is developed to achieve a dense planar winding bundle that can withstand medium voltage stress. An electrostatic shield layer is used to control the flow of common mode currents between the transformer windings. Silicon carbide loaded nonlinear stress grading materials are synthesized and characterized for the purposes of optimizing the transformer stress grading. An aqueous colloidal solution of silicon carbide microparticles is synthesized and shown to produce finished coatings with more consistent electrical properties than both commercial and custom-produced SiC loaded enamels. The prototype transformer is PD free up to 14.8kV, achieves 15.9kW/liter power density, and 99.1% peak efficiency.