Abstract:

Taking the single-phase single-stage grid-connected photovoltaic inverters as the research object, a life prediction method of photovoltaic inverters based on mission profile was proposed.Taking the actual temperature and light intensity in a year as the mission profile, the IGBT thermal resistance model was imported into PLECS, and the junction temperature data was obtained after several thermal simulations.One year junction temperature profile of IGBT was obtained by the interpolation table lookup method, and the lifetime of individual IGBT was predicted by the rain-flow counting method and the analytical life model.Finally, the life distribution function of a single IGBT was obtained based on Monte Carlo simulation method, and the unreliability distribution function of four IGBTs of single-phase single-stage inverter was obtained by series block diagram method.The predicted results are in line with the actual situation that the service life of photovoltaic inverters is usually less than 15 years.

Key words: photovoltaic inverter, interpolation table lookup method, rain-flow counting method, life prediction, Monte Carlo simulation method