1. Determination of neutron flux redistribution factors for a typical pressurized water reactor ex-core measurements using Monte Carlo techniqueTanja Goričanec, Bor Kos, Klemen Ambrožič, Andrej Trkov, Luka Snoj, Marjan Kromar, 2023, izvirni znanstveni članek Opis: In a typical pressurized water reactor, neutron detectors located outside the reactor core monitor reactor power. In addition, they are also used to measure the reactivity of the control rods. A novel approach to calculate the ex-core neutron detector response in a typical pressurized water reactor using the Monte Carlo technique is presented. A detailed ex-core model of the Krško nuclear power plant was developed using the Monte Carlo neutron transport code MCNP. Due to the location of the ex-core neutron detectors, the hybrid code ADVANTG is used to generate variance reduction parameters to accelerte the convergence of the results outside the reactor core. To use ADVANTG, the fixed neutron source had to be reconstructed from the criticality core calculation. This paper presents the sensitivity analysis of the response of the ex-core detectors to the neutron data libraries used, the description of the fixed neutron source and the ADVANTG parameters. It was found that a pin-wise description of the neutron source for at least two rows of fuel assemblies at the core periphery is necessary for accurate results. Our results show the importance of a correct description of the prompt neutron spectra in the high energy region and the impact this has on the response of the ex-core detectors. The method in which the prompt neutron fission spectra for important fission nuclides are weighted by the calculated reaction rates has been shown to be the best approximation, with deviations from the reference calculation within statistical uncertainty. The effect of nuclear data libraries on the response of the ex-core detector was investigated, and the difference between the ENDF/B-VII.0 and the ENDF/B-VIII.0 nuclear data libraries was ∼11%. When the deficient evaluation of the 56Fe isotope included in the ENDF/B-VIII.0 nuclear data library was replaced by the improved evaluation from the IAEA INDEN project, the differences decreased to ∼3.7%. In addition, neutron flux redistributions due to control rod movement were investigated and flux redistribution factors were updated using Monte Carlo particle transport methods. The reaction rate redistribution factors obtained with methods presented in this paper are within 1% agreement with the currently used factors.
Ključne besede: MCNP, ADVANTG, pressurized water reactor, Monte Carlo neutron transport, control rod, neutron flux redistribution factor, rod insertion, krško nuclear power plant
Objavljeno v DKUM: 29.11.2024; Ogledov: 0; Prenosov: 2
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2. A Machine Learning Application for the Energy Flexibility Assessment of a Distribution Network for ConsumersJaka Rober, Leon Maruša, Miloš Beković, 2023, izvirni znanstveni članek Ključne besede: flexibility, baseline, demand response, distribution transformer, congestion management, power flow control, peak shaving, load shifting, predictive models, machine learning
Objavljeno v DKUM: 05.01.2024; Ogledov: 386; Prenosov: 41
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3. International Conference Fluid Power 2019 : Conference Proceedings2019 Opis: The International Fluid Power Conference is a two day event, intended for all those professionally-involved with hydraulic or pneumatic power devices and for all those, wishing to be informed about the ‘state of the art’, new discoveries and innovations within the field of hydraulics and pneumatics. The gathering of experts at this conference in Maribor has been a tradition since 1995, and is organised by the Faculty of Mechanical Engineering at the University of Maribor, in Slovenia. Fluid Power conferences are organised every second year and cover those principal technical events within the field of fluid power technologies in Slovenia, and throughout this region of Europe. This year's conference is taking place on the 19th and 20th September in Maribor.
Ključne besede: fluid power technology, components and systems, control systems, fluids, maintenance and condition monitoring
Objavljeno v DKUM: 24.02.2020; Ogledov: 1383; Prenosov: 44
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4. The development of ARM-based portable and adaptable power supply : magistrsko deloTomislav Brlek, 2019, magistrsko delo Opis: This master’s thesis describes a development of a portable and adjustable power supply. The first part of the thesis introduces us to the working principle of power supplies in general. Next, we present a functional design of a portable and adjustable power supply and a list of its required functionalities. Chapter “switched-mode power supplies” introduces us to the theoretical basics of the said power supplies, while chapter “linear regulators” introduces us to different types of linear regulators and tells us more about how they work. Everything regarding which microcontroller was used and why it was used is described in the “ARM microcontroller” chapter. Besides microcontrollers, it also talks about which integrated development environment is used and how the microcontroller is programmed. A full and detailed description of each part of the analog circuitry can be found in the chapter “describing the development of the portable and adjustable power supply”. Lastly, the user interface is described in detail.
Ključne besede: portable power supply, ARM processor, variable laboratory bench power supply, LCD touchscreen, energy efficient, lithium battery, battery charger, voltage control
Objavljeno v DKUM: 13.11.2019; Ogledov: 1164; Prenosov: 140
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5. The impact of wind-power generation on the planning of regulating reserveDunja Srpak, 2018, doktorska disertacija Opis: This doctoral thesis focuses on the efficient management of a power system with a large share of wind-power generation and on the methods for planning the operating reserve. The approach proposed in this research involves the use of data directly from the network’s dispatch center and the forecasting systems, as well as already existing day-ahead plans for wind and load power to determine the regulating reserve for the load frequency control (LFC). The same principle is used to find the optimal regulating reserve distribution (RRD) between the available generation units in the system for automatic generation control. It is developed using iterative power-flow computation with a reactive power correction and a stochastic search algorithm for transmission-loss minimization. Moreover, variations in the generation of individual wind-power plants (WPPs) from the plan are considered in the optimal RRD.
A special focus of this research has been put on the Croatian power system due to the accessibility of relevant information and operating data. The obtained results of the testing with actual data from the Croatian power system indicate substantial savings in ancillary service costs for the LFC, while ensuring safe system operation. The considerable impact of variations from the plan for each individual WPP generation on the optimal RRD was also identified. Comparing the results for the daily sum of regulating reserves obtained with the proposed and the currently used approaches, the corresponding costs indicate a total saving of 21.2% for all 12 selected days in 2015 when using the proposed approach. In practice, a part of the reserve can be slow, i.e., with a lower unit price, thus the savings would be even higher. Furthermore, the obtained optimal RRD computed according to the proposed approach was compared with four commonly used RRDs in Croatia. The results obtained using the proposed approach indicate a decrease in the total transmission losses of between 1% and 2%. With a larger share of the generation from the WPPs and with more dispersed locations of the WPPs and regulating power plants a larger reduction in the transmission losses is expected.
Ključne besede: Evolutionary computation, Frequency control, Optimization, Power system, Regulating reserve, Wind power generation
Objavljeno v DKUM: 28.03.2018; Ogledov: 1951; Prenosov: 432
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6. The impact of wind-power generation on the planning of regulating reserveDunja Srpak, Boštjan Polajžer, 2017, izvirni znanstveni članek Opis: This paper presents new approach to the optimal distribution of the regulating reserve (RR) in a set of available regulating generation units. It is developed using evolutionary computation for the transmission-loss minimization and power-flow computation by applying the iterative method with a reactive power correction for voltage control. The approach involves the use of actual operating data directly from the network’s dispatch centre as well as daily and hourly plans of wind and load power for determining the RR requirements for the load frequency control (LFC). By testing the proposed approach on a case study, the possibility of implementing it on real power systems is demonstrated. The obtained results of the testing with actual data from the Croatian control area indicate substantial savings in ancillary service costs for the LFC and the considerable impact of different variations from the plan of each individual wind-power plant on the optimal RR distribution.
Ključne besede: evolutionary computation, frequency control, optimization, power systems, wind power generation
Objavljeno v DKUM: 24.10.2017; Ogledov: 1476; Prenosov: 381
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7. International conference Fluid power 2017 : September 14th - 15th 2017, Maribor, Slovenia (conference proceedings)2017, zbornik recenziranih znanstvenih prispevkov na mednarodni ali tuji konferenci Opis: The International Fluid Power Conference is a two day event, intended for all those professionally-involved with hydraulic or pneumatic power devices and for all those, wishing to be informed about the ‘state of the art’, new discoveries and innovations within the field of hydraulics and pneumatics.
The gathering of experts at this conference in Maribor has been a tradition since 1995, and is organised by the Faculty of Mechanical Engineering at the University of Maribor, in Slovenia. Fluid Power conferences are organised every second year and cover those principal technical events within the field of fluid power technologies in Slovenia, and throughout this region of Europe. This year's conference is taking place on the 14th and 15th September in Maribor.
We wish all participants at the International Conference-Fluid Power 2017 continued successful professional work, and hope that we have yet again added another small piece within the mosaic of fluid power.
Ključne besede: fluid power technology, components and systems, control systems, fluids, maintenance, monitoring
Objavljeno v DKUM: 28.09.2017; Ogledov: 1594; Prenosov: 174
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8. SOFT SWITCHING FOR IMPROVING THE EFFICIENCY AND POWER DENSITY OF A SINGLE-PHASE CONVERTER WITH POWER FACTOR CORRECTIONTine Konjedic, 2015, doktorska disertacija Opis: This thesis investigates the possibilities for increasing the power conversion efficiency and power density of a single-phase single-stage AC-DC converter with power factor correction capability. Initially, the limitations are investigated for simultaneous increase of power density and efficiency in hard switched bidirectional converters. The switching frequency dependent turn-on losses of the transistors have been identified as the main limiting factor. In order to avoid the increase in total power losses with increasing the switching frequency, a control approach is proposed for achieving zero voltage switching transitions within the entire operating range of a bidirectional converter that utilizes power transistors in a bridge structure. This approach is based on operation in the discontinuous conduction mode with a variable switching frequency. Operation in the discontinuous conduction mode ensures the necessary reversed current that naturally discharges the parasitic output capacitance of the transistor and thus allows this transistor to be turned on at zero voltage. On the other hand, the varying switching frequency ensures that the converter operates close to the zero voltage switching boundary, which is defined as the minimum required current ripple at which zero voltage switching can be maintained. Operation with the minimum required current ripple is desirable as it generates the lowest magnetic core losses and conduction losses within the power circuit.
The performance and effectiveness of the investigated approach were initially verified in a bidirectional DC-DC converter. A reliable zero voltage switching was confirmed over the entire operating range of a bidirectional DC-DC converter, as well as the absence of the reverse recovery effect and the unwanted turn-on of the synchronous transistor. In order to justify its usage and demonstrate its superior performance, the proposed zero voltage switching technique was compared with a conventional continuous conduction mode operation which is characterized by hard switching commutations. After successful verification and implementation in a bidirectional DC-DC converter, the investigated zero voltage switching approach was adapted for usage in an interleaved DC-AC converter with power factor correction capability. Comprehensive analysis of the converter's operation in discontinuous conduction mode with a variable switching frequency was performed in order to derive its power loss model. The latter facilitated the design process of the converter's power circuit. A systematic approach for selecting the converter's power components has been used while targeting for an extremely high power conversion efficiency over a wide operating range and a low volume design of the converter.
The final result of the investigations performed within the scope of this thesis is the interleaved AC-DC converter with power factor correction capability. Utilization of interleaving allows for increasing the converter's power processing capability, reduces the conducted differential mode noise and shrinks the range within which the switching frequency has to vary. The proposed zero voltage switching control approach was entirely implemented within a digital signal controller and does not require any additional components within the converter's circuit. The experimental results have confirmed highly efficient operation over a wide range of operating powers. A peak efficiency of 98.4 % has been achieved at the output power of 1100 W, while the efficiency is maintained above 97 % over the entire range of output powers between 200 W and 3050 W.
Ključne besede: zero-voltage switching, power factor correction, variable switching frequency, discontinuous conduction mode, reverse recovery, unwanted turn-on, bidirectional DC-DC converter, bidirectional AC-DC converter, control of switching power converters
Objavljeno v DKUM: 13.10.2015; Ogledov: 2269; Prenosov: 241
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