Nanocrystalline Copper aluminate (CuAl 2 O 4 ) was prepared by sol-gel technique using aluminum nitrate, copper nitrate, diethylene glycol monoethyl ether and citric acid were used as precursor materials. This method starts from of the precursor complex, and involves formation of homogeneous solid intermediates, reducing atomic diffusion processes during thermal treatment. The formation of pure crystallized CuAl 2 O 4 nanocrystals occurred when the precursor was heat-treated at 600°C in air for 2 h. The stages of the formation of CuAl 2 O 4 , as well as the characterization of the resulting compounds were done using thermo-gravimetric analysis, X-ray diffraction, scanning electron microscopy and Fourier transform infrared spectroscopy. The products were analyzed by transmission electron microscopy and ultraviolet-visible (UV-Vis) spectroscopy to be round, about 17-26 nm in size and E g = 2.10 eV.

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In order to increase the low voltage of renewable energy systems to a relatively high bus voltage for the downstream DC-AC grid-connected inverter, a new DC-DC switched-capacitor converter with the potential of output voltage regulation is proposed. The operational principles, with regard to the specific switching conditions, are provided the relationships for the parameter design and efficiency calculation. The topology makes it possible to integrate the high voltage gain and excellent output regulation that open a huge area of applications and create the possibility of maximum power point tracking (MPPT), which is an important advantage of proposed structure. Moreover, the most important advantages of the proposed structure are continuous input current, variety of the DC voltage source values, and the cost of the converter in comparison with the conventional structures. A comparison with other similar structures is given to show the merits of the proposed topology. Finally, the experimental results are presented to clarify the theory and feasibility of the proposed converter. K E Y W O R D S DC-DC power conversion, high step-up voltage gain, switched capacitor (SC)

Up to now, many modulation techniques have been proposed for neutral point clamped (NPC) inverters. In this paper, for the first time, a general methodology is applied to calculate and compare the failure analysis and reliability of NPC inverter with most commonly used control strategies. Also, the mean time to failure (MTTF) of NPC inverter is derived for different control strategies. It is demonstrated that the key feature of control strategies in determining the reliability of inverter is their loss distribution among the switches. The failure rate of components that is relevant to this study and junction temperature calculation is developed, then conduction losses and switching losses of switches for different control strategies are calculated. Finally, the most reliable control strategy is identified. Experimental results obtained have promptly justified the theoretical analysis and outlined procedure.

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Experience shows that semiconductor switches in power electronics systems are the most vulnerable components. One of the most common ways to solve this reliability challenge is componentlevel redundant design. There are four possible configurations for the redundant design in component-level. This paper presents a comparative reliability analysis between different componentlevel redundant designs for solid state fault current limiter (SSFCL). The aim of the proposed analysis is to determine the more reliable component-level redundant configuration. The mean time to failure (MTTF) is used as the reliability parameter. Considering both fault types (open circuit and short circuit), the MTTFs of different configurations are calculated. It is demonstrated that more reliable configuration depends on the junction temperature of the semiconductor switches in the steady state. That junction temperature is a function of i) ambient temperature, ii) power loss of the semiconductor switch and iii) thermal resistance of heat sink. Also, results' sensitivity to each parameter is investigated. The results show that in different conditions, various configurations have higher reliability. The experimental results are presented to clarify the theory and feasibility of the proposed approaches. At last, levelized costs of different configurations are analyzed for a fair comparison. Nomenclature λO.COpen circuit rate of unidirectional switch (failures per million calendar hours or FIT,