Third Harmonic Injection Method for Reliability Improvement of Single-Phase PV Inverters

Abstract

In the last decades, it is observed an increasing of Photovoltaic (PV) systems connected into the grid. In this context, the photovoltaic inverter reliability has became a target of study for many researchers and professionals in the area. In addition, the dc-link capacitor has been reported as one of the most critical components in the PV inverter. Regarding to the single-phase PV inverter, the voltage and current of the dc-link capacitor present a second harmonic component which directly affect its reliability. In order to solve this problem, a third harmonic current injection by the PV inverter is proposed in this work. Analysis of power losses, thermal stress and reliability are performed in the dc-link capacitor. In addition, the effects on the semiconductor devices are also considered. The results show the improvement in the dc-link capacitor reliability due to the proposed methodology. Also, it is shown that the third harmonic current insertion does not affect the PV inverter efficiency.