Enhancing reliability of photovoltaic power electronic converters under dynamic irradiance conditions

Abstract

This paper presents a novel temperature-controlled maximum power point tracking (MPPT) algorithm for lifetime improvement of a photovoltaic (PV) converter under dynamic irradiance conditions. The proposed algorithm controls and limits the junction temperature change rate of switching devices, reducing the thermal stress and drastically reducing the damage received, hence improving the reliability and lifetime of power converters in PV systems. To evaluate the damage reduction, a lifetime estimation technique is applied which is composed of a Foster thermal model, a rainflow counting algorithm and an empirical lifetime model. Moreover, in this paper the energy and life consumption are calculated with the application of lookup tables to reduce computation time. The effectiveness of the proposed algorithm is verified using extensive simulations and by comparing energy generated and life consumption under irradiance profiles for different cloud conditions. The temperature-controlled algorithm is applied in parallel with a normal MPPT algorithm to a 10 kW photovoltaic system and results are compared using irradiance data from the province of Quebec, Canada to validate its efficacy. The obtained results show that for very variable cloud conditions, the modified algorithm managed to reduce the life consumption by 4.68 % at no extra cost, with just 0.08 % of energy generation reduction, proving its effectiveness.