Multi-Physics Reliability Modeling of High-Frequency Electromagnetic Transformers in Solid-State Transformer Systems

High-frequency electromagnetic transformer (HFET) is one of the critical components in a solid-state transformer (SST) system, as it can provide galvanic isolation and voltage conversion between primary and secondary sides. Although SSTs are well-known for multiple beneficial features, there are reliability concerns with the HFET, especially for medium-voltage or high-voltage systems configured with fast-switching wideband gap power converters. In this paper, comprehensive multi-physics reliability modeling is presented to fully investigate the different physics of the SST systems. To this end, electromagnetic analysis by finite element method is first carried out to acquire the performance characteristics of the HFET. Afterwards, temperature distribution of the HFET is obtained based on electromagnetic results such as winding and core losses. Finally, electrostatic simulation is conducted to examine the effects of voids, which contributes to partial discharging on the dielectric strength of the insulation system. Since the three disciplines are closely related to each other, an innovative lifetime estimation model is proposed to incorporate the effect of insulation degradation due to partial discharging on the aging acceleration of the transformer in order to improve the accuracy of the lifetime estimation.