Effect of thermal stress on the life of DC link capacitors for smart grid

Abstract

Abstract Thermal stress is an important factor affecting the life of a DC link capacitor (DCLC). However, relevant studies on thermal stress mechanism directly influencing the lifetime of the capacitor are rarely reported. In this paper, the thermal polymerization of DCLC has been analyzed, and the relevant experimental platforms have been developed to evaluate the breakdown strength of DCLC at two thermal polymerization temperatures (TPTs). Simultaneously, the aging analysis of DCLC at different TPTs and the accelerated lifetime measurements at various temperatures were also executed to attain insights into the influence of thermal stress on the lifetime of DCLC. The results showed that the stress caused by thermal polymerization and working temperature influenced the breakdown voltage capability and the lifetime of DCLC. With an increase in TPT by 5 °C, a step-increase in the withstand voltage capability of DCLC from 7,000 V to 7,200 V was observed that demonstrated an enhancement of 2.86%in the breakdown strength performance. Correspondingly, the lifetime of DCLC with a capacitance change rate of -3% enhanced from 1,500 hours to 1,700 hours. However, severe deterioration in the life span of DCLC from 4,200 hours to 500 hours was observed with an increasing operating temperature from 55 °C to 85 °C, respectively. The lifetime could be enhanced by increasing the thermal polymerization temperature as well as reducing the working temperature. The presented results could be termed a harbinger for industrial production of high-performance DCLC with enhanced lifetime that augers well for high-power applications.