Effect of Current Distortion and Unbalanced Loads on Semiconductors Reliability

This article presents a reliability analysis of a 4-wire grid-tied inverter under different loading conditions, considering unbalanced loads and harmonic distortion in the current consumed. The proposed power converter is used as a case study to assess the impact of current disturbances on the semiconductors' reliability. The 4-wire inverter analyzed is implemented with a 3-leg SiC MOSFET power module and a neutral wire connected to the midpoint of the DC-link. The analysis is founded on the literature's reliability curves for power switches. As key take-home findings, the addition of harmonic content in the load current plays a dominant role in the semiconductors' expected lifetime, especially for the low-frequency harmonics, e.g., third harmonic. Furthermore, the phase delay of the harmonic current content is revealed as a critical factor in the semiconductor's reliability. Additionally, the existence of unbalanced loads substantially modifies the reliability of the semiconductors of the inverter. The results confirm that converters' reliability is highly dependent on the loading conditions and harmonic content, so identifying the most critical conditions is inevitable.