Effect of High-Frequency Transformer Parasitic Capacitances on Operation of Solid-State Transformers

This paper examines the effects of parasitic capacitances of the high-frequency transformer on matrix converter based solid-state transformer (SST) operation. SSTs involve high frequency transformers for isolation. With the increasing trend towards high-frequency operation to achieve higher power densities, the parasitic capacitances of the transformer become prominent. The inclusion of these capacitances modifies the equivalent circuit of the transformer. The current research does not take into account this modification. It is essential to identify the effects of this modified equivalent circuit on the operation of SST for better predictability and reliability. This paper also quantifies experimentally the parasitic ca-pacitances associated with the high-frequency nanocrystalline transformer. The effect of these parasitic capacitances is observed on the transformer input current and output voltage. These system quantities are essential for pulse width modulation of the matrix converter-based SST. A comprehensive examination of these effects is performed which includes the variation of other involved circuit parameters along with parasitic capacitances such as transformer leakage inductance, resistance, connecting wire inductance and resistance. This examination also lends useful insights into high-frequency transformer design for SSTs. The analysis can also be applied to SST topologies which involve high frequency transformer and similar voltage and current waveforms.