Wear-Out Analysis of a Grid-Forming Two-Phase Three-Wire Converter Under Unbalanced Load

Abstract

The grid-forming converter that supplies voltage magnitude and frequency is a key element for isolated remote communities, and then wear-out analysis is an essential figure of merit. Therefore, this paper proposes the two-phase three-wire (2$\Phi$3 W) grid forming converter applied in a case study of isolated riverside communities in the Brazilian Amazon region. The proposed xyn-converter displaces the voltage line angle in 180$^{\circ }$, differing from $\alpha \beta$n-converter and abn-converter that displace voltage line angle in 90$^{\circ }$ and 120$^{\circ }$ respectively. First, the authors have also proposed a semiconductor current stress evaluation for 2$\Phi$3 W converters comparing the RMS current. Then, the lifetime evaluation of the three evaluated grid-forming converters is conducted. The results show that the converter operating in the xyn-converter presents the highest reliability among the three converters. Finally, the thermal stress analysis is validated by means of a 2$\Phi$3 W converter prototype with an open semiconductor module. For the evaluated converters, the xyn-converter has the least thermal stress for balanced and unbalanced load conditions and therefore the longest lifespan. The experimental validation shows that the average temperature of the xyn-converter is 19.4% and 23.3% lower than both the abn-converter and the $\alpha \beta$n-converter under balanced load conditions.

Keywords

• Grid-forming converter
• isolated AC power grids
• lifetime consumption
• wear-out