Lifetime Of Power Converter Research Articles

Enhancing reliability of photovoltaic power electronic converters under dynamic irradiance conditions

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.

An Online and Noninvasive Technique for the Condition Monitoring of Capacitors in Boost Converters

Capacitors usually determine the overall lifetime of power converters since they are mainly responsible for breakdowns. Their failure results from the deterioration of their dielectric, the production of gases, and, eventually, their explosion. This process leads to an increase in the capacitor equivalent series resistance (ESR) and a decrease in its capacitance value for both electrolytic and metalized polypropylene film (MPPF) capacitors. In this paper, a novel noninvasive technique for capacitor diagnostic in Boost converters is presented. It can easily be applied online and even in real time, and it is suitable for the operation in both continuous current mode (CCM) and discontinuous current mode (DCM). The technique is based on the double estimations of the ESR and the capacitance, improving the diagnostic reliability. This way, predictive maintenance is provided, and it is possible to alarm for capacitor replacement, avoiding downtime. As the method is intended for railway high-power applications, it has been conceived neither to add any additional hardware in the power stage nor to even slightly modify it. To demonstrate and validate the effectiveness and accuracy of the proposed technique, several simulations and experimental results are discussed in a small prototype. In this prototype, the software for real-time estimation is programmed in a low-cost digital signal processor (DSP).