Interactions Analysis and Life Modeling for High-Frequency Transformers Insulation Under Multistress

Abstract

High-frequency transformers (HFTs) are key devices in solid-state transformers (SSTs). Accurate prediction of the remaining life of the HFT is essential to ensure the reliability of the SST. The insulation of the HFT withstands multistress of high-frequency pulsewidth modulation (PWM) voltage, and high temperature. These severe conditions may lead to its accelerated aging and failure. However, the life characteristics of the HFT insulation subjected to multistress of high voltage, high frequency, and high temperature are not well known introducing a big uncertainty for life prediction and reliability assessment of the HFT, and there is a lack of life model that can be used for HFT insulation considering multistress. This article focuses on the investigation of the interaction between multistress of high voltage, high frequency, and high temperature and it proposes a life model applicable to HFT insulation. A high-frequency PWM voltage electrothermal aging test platform is established, which is capable of generating PWM voltage waveforms up to 10 kV and 100 kHz. The electrothermal aging test is designed and analyzed with the response surface method and analysis of variance. The results revealed a significant effect of switching frequency on the insulation life and non-negligible interactions among the three factors, voltage level, switching frequency, and temperature, at high frequencies. Based on these findings, an electro-thermal-frequency life model for HFT insulation is proposed. Finally, the mechanism of insulation aging and breakdown mechanism at high frequencies is analyzed, and the potential application of the proposed life model is discussed. The outcomes of this research offer valuable references and serve as the foundation for predictive maintenance, insulation system design, and reliability analysis of HFTs under multistress.