Optimal Operation of a Photovoltaic Integrated Captive Cogeneration Plant with a Utility Grid Using Optimization and Machine Learning Prediction Methods

The World Energy Council, in its 2019 World Energy Scenarios Report, advised policymakers to identify innovative opportunities for the integration of renewable energy resources into existing electrical power systems to achieve a fast and affordable solution. However, large-scale industries with cogeneration units are facing problems in handling the higher penetration levels of intermittent renewable energies. This paper addresses large-size photovoltaic power integration problems and their optimal operation. This work considers the case of a chemical industry having both cogeneration power and solar photovoltaics. Here, a modified firefly algorithm and a hybrid power resource optimization solver are proposed. The results of the proposed method are compared with other benchmark techniques, to confirm its advantages. The proposed techniques can be used in industries having cogeneration power plants with photovoltaics for better optimization and to meet the guidelines specified in IEEE 1547. The voltage ramp index is proposed to determine the voltage ramp up and down with intermittent solar irradiance. Additionally, a machine learning technique is used to predict the cogeneration plant efficiency at different loads and the solar irradiance under varying weather conditions. Finally, this paper proposes the effectiveness of the modified heuristic technique and certain guidelines, including solvers for industrial use.

Sequential activation of multiple persistent inward currents induces staircase currents in serotonergic neurons of medulla in ePet-EYFP mice

Persistent inward currents (PICs) are widely reported in rodent spinal neurons. A distinctive pattern observed recently is staircase-like PICs induced by voltage ramp in serotonergic neurons of mouse medulla. The mechanism underlying this pattern of PICs is unclear. Combining electrophysiological, pharmacological, and computational approaches, we investigated the staircase PICs in serotonergic neurons of medulla in ePet-EYFP transgenic mice (postnatal days 1–7). Staircase PICs induced by 10-s voltage biramps were observed in 70% of serotonergic neurons ( n = 73). Staircase PICs activated at −48.8 ± 5 mV and consisted of two components, with the first PIC of 45.8 ± 51 pA and the second PIC of 197.3 ± 126 pA ( n = 51). Staircase PICs were also composed of low-voltage-activated sodium PIC (Na-PIC; onset −46.2 ± 5 mV, n = 34), high-voltage-activated calcium PIC (Ca-PIC; onset −29.3 ± 6 mV, n = 23), and high-voltage-activated tetrodotoxin (TTX)- and dihydropyridine-resistant sodium PIC (TDR-PIC; onset −16.8 ± 4 mV, n = 28). Serotonergic neurons expressing Na-PIC, Ca-PIC, and TDR-PIC were evenly distributed in medulla. Bath application of 1–2 μM TTX blocked the first PIC and decreased the second PIC by 36% ( n = 23, P < 0.05). Nimodipine (25 μM) reduced the second PIC by 38% ( n = 34, P < 0.001) without altering the first PIC. TTX and nimodipine removed the first PIC and reduced the second PIC by 59% ( n = 28, P < 0.01). A modeling study mimicked the staircase PICs and verified experimental conclusions that sequential activation of Na-PIC, Ca-PIC, and TDR-PIC in order of voltage thresholds induced staircase PICs in serotonergic neurons. Further experimental results suggested that the multiple components of staircase PICs play functional roles in regulating excitability of serotonergic neurons in medulla. NEW & NOTEWORTHY Staircase persistent inward currents (PICs) are mediated by activation of L-type calcium channels in dendrites of mouse spinal motoneurons. A novel mechanism is explored in this study. Here we report that the staircase PICs are mediated by sequentially activating sodium and calcium PICs in serotonergic neurons of mouse medulla.

Is the Dry-Band Characteristic a Function of Pollution and Insulator Design?

This paper assesses the dry-band formation and location during artificial pollution tests performed on a 4-shed 11kV insulator with conventional and textured surface designs in a clean-fog chamber and with the application of a voltage ramp-shape source. The different designs present the same overall geometrical dimensions, but the textured ones are characterized by the application of a patented insulator surface design. Three pollution levels, extremely high, high and moderate, were considered. A newly developed MATLAB procedure is able to automatically recognize the perimeter of the insulator, the trunk and shed areas on infra-red recordings. In addition, using the vertical axis identification, all trunks are subdivided into zones and into left and right areas, significantly increasing the capability of abnormalities detection. Any temperature increase within these areas enables to detect the appearance and the extension of dry bands. The results of the analysis of the statistical location and extension development over time of the dry bands during these set of comparative tests show a clear distinction between designs and pollution levels. These results may offer interesting design guidelines for dry-band control.

Metallized ceramic substrate with mesa structure for voltage ramp-up of power modules

As the available wide bandgap semiconductors continuingly increase their operating voltages, the electrical insulation used in their packaging is increasingly constrained. More precisely the ceramic substrate, used in demanding applications, represents a key multi-functional element is being in charge of the mechanical support of the metallic track that interconnects the semiconductor chips with the rest of the power system, as well as of electrical insulation and of thermal conduction. In this complex assembly, the electric field enhancement at the triple junction between the ceramic, the metallic track borders and the insulating environment is usually a critical point. When the electrical field at the triple point exceeds the critical value allowed by the insulation system, this hampers the device performance and limits the voltage rating for future systems. The solution proposed here is based on the shape modification of the ceramic substrate by creating a mesa structure (plateau) that holds the metallic tracks in the assembly. A numerical simulation approach is used to optimize the structure. After the elaboration of the structures by ultrasonic machining we observed a significant increase (30%) in the partial discharge detection voltages, at 10 pC sensitivity, in a substrate with a mesa structure when comparing to a conventional metallized ceramic substrate.