Current Issue : April - June Volume : 2020 Issue Number : 2 Articles : 5 Articles
Modern multi-MW wind generators have used multi-level converter structures as well as\nparallel configuration of a back to back three-level neutral point clamped (3L-NPC) converters to\nreduce the voltage and current stress on the semiconductor devices. These configurations of converters\nfor offshore wind energy conversion applications results in high cost, low power density, and complex\ncontrol circuitry. Moreover, a large number of power devices being used by former topologies results\nin an expensive and inefficient system. In this paper, a novel bi-directional three-phase hybrid\nconverter that is based on a parallel combination of 3L-NPC and â??nâ?? number of Vienna rectifiers have\nbeen proposed for multi-MW offshore wind generator applications. In this novel configuration, total\npower equally distributes by sharing of total reference current in each parallel-connected generator\nside power converter, which ensures the lower current stress on the semiconductor devices. Newly\nproposed topology has less number of power devices compared to the conventional configuration of\nparallel 3L-NPC converters, which results in cost-effective, compact in size, simple control circuitry,\nand good performance of the system. Three-phase electric grid is considered as a generator source for\nimplementation of a proposed converter. The control scheme for a directly connected three-phase\nsource with a novel configuration of a hybrid converter has been applied to ratify the equal power\ndistribution in each parallel-connected module with good power factor and low current distortion.\nA parallel combination of a 3L-NPC and 3L-Vienna rectifier with a three-phase electric grid source\nhas been simulated while using MATLAB and then implemented it on hardware. The simulation and\nexperimental results ratify the performance and effectiveness of the proposed system....
This paper shows a methodology to obtain metallic uranium through a magnesiothermy\nprocess. Chile has two experimental reactors operated by the\nâ??Chilean Nuclear Energy Commissionâ? (CCHEN). One is 5 MW and the\nother is 10 MW. In order to fulfill international agreements about nuclear\nenergy for testing purposes of these reactors, CChEN purchased 19.9%\nenriched uranium hexafluoride, also known as the limit of Low Enriched\nUranium (LEU). Due to the capacity of these reactors, they need high-density\nuranium compounds for their fuel, in order to work with LEU. For this reason,\nthe uranium needs a previous conversion into metallic uranium. The\nconversion laboratory carried out experiences for reduction of UF4 with Mg.\nThe main purpose of this study was to analyze the operating conditions under\nwhich the reduction reaction takes place, the designed method and the equipment\nand materials used. The raw material used was dehydrated UF4, prepared\nby electrolytic reduction and commercial purity Magnesium. The\nreaction took place in a cylindrical reactor made of low alloy steel, with a\nconic section in the lower part. The internal zone was coated with a 2.5 cm\nthick layer of CaF2. The process started by applying external heating, according\nto a heating program, developed specially for this purpose. The reduction\nreaction took place starting at 650DegreeC. The result was a cylinder of\nuranium metal and MgF2 slag. The crossed cut uranium cylinder showed a\nsmooth and homogeneous surface without inclusions of slag, pores or blisters.\nThe yield of the reaction was of the order of 75% with respect to the expected\ntheoretical value. The uranium cone obtained fulfilled the required\nconditions for source material for nuclear fuel fabrication, with a uranium\ncontent of 97.5%....
As key equipment in nuclear power plant, the reactor power control system is adopted to strictly control and regulate the reactor\npower of a PWR (pressurized water reactor) in a nuclear power plant. A well-optimized predictive control algorithm based on\nSDMC (stepped dynamic matrix controller) is developed and introduced in this paper and applied to the power regulation of a\nreactor power model. In addition, the test and verification of this application is conducted by two different methods and devices:\nthe virtual verification platform and the physical DCS (digital control system). The result of the verification suggests that the\napplication of SDMC gains a better performance in the maximum dynamic deviation, adjustment time, overshoot, and so on....
The aim of the paper described here was to clarify the potential of decreasing\nthe use of fossil fuels regionally. According to Finnish national obligations,\nthe use of oil and other fossil fuels should be minimised by 2030. The study\ncombines the regional consumption of primary energy sources with national\nobligations introduced in the national climate and energy strategy. This set\nup a basis when evaluating the regional state of future energy supply for 2030.\nThe paper utilises the region of South Savo as a case study. In the region, the\nconsumption of renewable energy sources is already above the national average,\nbut it can be increased further by 2030. Wood fuels and especially forest\nbiomass have regionally a major role. Local and national targets, support\nschemes and willingness to invest play key roles when increasing the use of\nrenewable energy sources in the future....
The Earth is under increasing stress owing to carbon emissions. Clean energy\nforms constitute an area of increasing technological interest. Geothermal\nenergy is a clean alternative energy form that can be harnessed from the\nEarthâ??s core. The use of geothermal energy resources is gaining substantial\ninterest in many countries, as an integral part of 21st century clean energy solutions\nand meeting stringent emission requirements. The objective of this\nresearch is to investigate an alternative approach to clean and renewable geothermal\nenergy utilization through geothermal ground water pressure applied\nwithin a water turbine. The groundwater pressure from the candidate geothermal\nsites considered is applied to drive a water turbine for the generation\nof electrical energy. The geothermal candidate sites are low-temperature (i.e .\n<60DegreeC) geothermal springs, where it is not beneficial to apply low temperatures\nin a Rankine cycle steam turbine due to the low enthalpy. Simple calculations\nare conducted to estimate the electrical energy output of each candidate\nsite. This may technically be regarded as a thermodynamic problem, albeit\none that does not require full thermodynamic cycle analysis. The results\nof the simple non-rigorous analysis indicate that the electrical energy generation\npotential is greater when using geothermal water pressure (2.5 MWe)\nthan when using low geothermal temperature (0.005 MWe)....
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