Methodology for bondwire lifetime evaluation of multifunctional PV inverter during harmonic current compensation

Abstract

Multifunctional photovoltaic (PV) inverters have been described as a suitable power quality solution in modern power systems based on distributed generation. The basic idea is to use the PV inverter to perform ancillary services, such as harmonic current compensation (HCC). Nevertheless, this extra functionality may affect the lifetime consumption of the PV inverter. Indeed, only few works in literature discuss this topic, since the lifetime evaluation procedure during HCC is not straightforward. In addition, the traditional methodology currently available in the literature cannot be easily extended to HCC operation. Therefore, this work proposes a new lifetime prediction methodology which considers the effects of both fundamental and harmonic currents injected by the PV inverter. The proposed methodology can take into account all the additional power cycling due to any harmonic current combination. Furthermore, the lifetime evaluation is carried out considering the mission profiles of solar irradiance, ambient temperature, harmonic current amplitude and phase angle. The obtained results indicate that HCC increases the number of temperature cycles and may significantly affect the PV inverter lifetime. When the ratio between the harmonic and fundamental current amplitudes increases, the PV inverter lifetime consumption also increases. In addition, a strong dependence between lifetime consumption and the harmonic phase angle is observed for low order harmonics, such as 3rd and 5th harmonics.