Search

As research and development of renewable and clean energy based systems is advancing rapidly, the nonlinear source emulator (NSE) is becoming very essential for testing of maximum power point trackers or downstream converters. Renewable and clean energy sources play important roles in both terrestrial and nonterrestrial applications. However, most existing NSEs have only been concerned with simulating energy sources in terrestrial applications, which may not be fast enough for testing of nonterrestrial applications. In this paper, a high-bandwidth NSE is developed that is able to simulate the behaviors of a typical nonlinear source under different critical conditions that can happen during their operations. The proposed 200-W NSE, which consists of a fourth-order output filter buck converter and a novel nonlinear small-signal reference generator, can quickly react not only to an instantaneous change in the input source but also to a load step between nominal and open circuit. Moreover, all of these operation modes have a very fast settling time of only 10 $\mu$ s, which is hundreds of times faster than that of existing works. This attribute allows for higher speed and a more efficient maximum power point tracking algorithm. The proposed NSE, therefore, offers a superior dynamic performance among devices of the same kind.

This paper gives a comprehensive comparison of two promising silicon carbide (SiC) switching devices, i.e. normally-off SiC MOSFET and a normally-on SiC JFET, as alternatives to a conventional state of the art Si IGBT. The comparison uses datasheet information to determine conduction losses, switching transition measurements for switching loss calculations and electrical power measurements in a boost converter. Using SiC switching devices, switching energies can be reduced by almost 70% and the forward voltages of such devices are much lower compared to the IGBT which then reduce the conduction losses. This reduction in semiconductor losses can increase overall converter efficiencies up to 0.4% at 20kHz or enable high frequency operation up to 100 kHz which then reduces the size and weight of the inductor by more than 75% while still achieving efficiencies over 98.3 %.

This paper describes modeling, fabrication and high power optical characterization of thin gold films embedded in silicon dioxide. The propagation vector of surface plasmon polaritons has been calculated by the effective index method for the wavelength range of 750-1700 nm and film thickness of 15, 30 and 45 nm. The fabrication process of such plasmonic waveguides with width in the range of 1-100 μm and their quality inspection are described. The results of optical characterization of plasmonic waveguides using a high power laser with the peak power wavelength 1064 nm show significant deviation from the linear propagation regime of surface plasmon polaritons at the average input power of 100 mW and above. Possible reasons for this deviation are heating of the waveguides and subsequent changes in the coupling and propagation losses.