Lifetime evaluation of three-phase multifunctional PV inverters with reactive power compensation

摘要

The multifunctional operation of photovoltaic inverters consists in providing ancillary services to the grid, such as reactive power injection, harmonic current compensation, frequency regulation and others. These extra activities can cause higher electro-thermo-mechanical stress in the inverter components, affecting their reliability. Hence, this work aims to analyze the multifunctional inverters reliability when the injection of a real industry reactive power profile is performed. The evaluation has been carried out on a grid-connected three phase photovoltaic system, considering a mission profile from Denmark. An equivalent thermal model is used to estimate the power devices junction temperature. Furthermore, a lifetime model applied to the Palmgren-Miner's rule is used to evaluate the inverter lifetime consumption. Afterward, a statistical analysis simulates several power devices operation scenarios, for the cases with and without reactive power injection. Finally, the results show that the reactive power injection has a considerable impact on the inverter reliability, reducing by 3 and 1.5 times the lifetime estimation when this service is performed without power restrictions and considering the dynamic power saturation, respectively.