Iskanje po katalogu digitalne knjižnice

Opis: Introduction. The integration of Renewable Energy Sources (RESs), particularly Wind Energy Conversion Systems (WECS), is vital for reducing reliance on fossil fuels and addressing climate change. However, this transition poses challenges, including ensuring grid stability in the face of intermittent RESs. Compliance with grid codes is crucial, with a focus on Low Voltage Ride Through (LVRT) capability. Problem. The intermittent nature of RESs, specifically in Permanent Magnet Synchronous Generator (PMSG) based WECS, presents challenges to grid stability during voltage dips. Goal. To enhance voltage stability and LVRT capability in PMSG-based WECS by integrating a Dynamic Voltage Restorer (DVR) with an energy storage device. This involves regulating the input DC voltage to the DVR using a type 2 fuzzy controller, adapting intelligently to changing conditions. Methodology. DVR, powered by an energy storage device, is strategically integrated with WECS. A type 2 fuzzy controller regulates the DC voltage to DVR. The rectified WECS output undergoes processing through an isolated flyback converter. A 31-level Cascaded H-Bridge Multilevel Inverter (CHBMLI) with PI control ensures high-quality AC output. Results. The validation of developed system is executed using MATLAB/Simulink revealing a reduced Total Harmonic Distortion (THD) value of 1.8 %, ensuring significance in LVRT capability. Originality. The strategic integration of DVR with PMSG-based WECS, addresses the LVRT challenges. The use of type 2 fuzzy controller for intelligent voltage regulation and a sophisticated multilevel inverter contributes to the uniqueness of proposed solution. Practical value. The developed system provides benefits by ensuring reliable LVRT capability in PMSG-based WECS with reduced THD of 1.8 % indicating improved grid compatibility. References 26, tables 5, figures 20.
Ključne besede: permanent magnet synchronous generator, wind energy conversion systems, low voltage ride through, type 2 fuzzy controller, isolated flyback converter, 31-level cascaded H-bridge multilevel inverter, PI controller
Objavljeno v DKUM: 06.11.2025; Ogledov: 0; Prenosov: 3
Celotno besedilo (1,51 MB)
Gradivo ima več datotek! Več...

Opis: This paper presents a novel sorting algorithm for modular multilevel inverters (MMCs) with integrated batteries, designed to ensure the uninterrupted operation of electric vehicles (EVs) under post-fault conditions. The proposed system structure consists of an MMC with four full-bridge modules per phase, where one module acts as a spinning reserve during normal operation. The algorithm addresses a single switch fault per phase by operating the faulted module in half-bridge mode, ensuring all batteries remain operational and maintaining full power output and battery capacity without any noticeable changes for the vehicle operator. Unlike conventional fault-tolerant strategies that often reduce power output or disable affected modules, the proposed algorithm isolates the faulty switch while preserving system output. This approach avoids derating and eliminates the need for immediate maintenance, enabling the EV to continue operating under fault conditions. Simulation and experimental results validate the effectiveness of the algorithm under a single switch fault scenario, demonstrating its ability to maintain autonomy and consistent power delivery. This work demonstrates a fault-tolerant MMC principle, offering a robust and scalable solution for enhancing reliability and user satisfaction in EV power systems.
Ključne besede: modular multilevel converter, fault tolerance, redundancy, uninterrupted operation, sorting algorithm
Objavljeno v DKUM: 09.04.2025; Ogledov: 0; Prenosov: 9
Celotno besedilo (10,18 MB)

Opis: Electric vehicles, especially cars, have been in the spotlight for some time now. In the focus of environmentalists, engineers, users, media, etc. With the growth and advancement of the market for such vehicles, other electric vehicles are also focussing on. One of such vehicles is boats, particularly smaller boats up to 8–10 meters in length. Of course, the biggest problem here is charging. The general idea is to use battery modules that can be easily carried and enable hot swapping. This paper investigates scenarios and simulations of the control system for hot swapping of the battery module. Simulations of connection of two and three battery modules to parallel operation and current control are presented in this paper, as well as applied control rules.
Ključne besede: battery pack, battery modules, parallel connection, Bidirectional multiple input single output synchronous DC/DC converter, BMISO DC/DC converter, Hotplugin, Smart SoC control, Advanced SoC control
Objavljeno v DKUM: 08.04.2024; Ogledov: 370; Prenosov: 21
Celotno besedilo (880,89 KB)
Gradivo ima več datotek! Več...

Opis: A new method for the automated measurement of the hysteresis of the temperature-compensated inductance-to-frequency converter with a single quartz crystal is proposed. The new idea behind this method is a converter with two programmable analog switches enabling the automated measurement of the converter hysteresis, as well as the temperature compensation of the quartz crystal and any other circuit element. Also used is the programmable timing control device that allows the selection of different oscillating frequencies. In the proposed programmable method two different inductances connected in series to the quartz crystal are switched in a short time sequence, compensating the crystal’s natural temperature characteristics (in the temperature range between 0 and 50 °C). The procedure allows for the measurement of the converter hysteresis at various values of capacitance connected in parallel with the quartz crystal for the converter sensitivity setting at selected inductance. It, furthermore, enables the measurement of hysteresis at various values of inductance at selected parallel capacitance (sensitivity) connected to the quartz crystal. The article shows that the proposed hysteresis measurement of the converter, which converts the inductance in the range between 95 and 100 μH to a frequency in the range between 1 and 200 kHz, has only 7 × 10−13 frequency instability (during the temperature change between 0 and 50 °C) with a maximum 1 × 10−11 hysteresis frequency difference.
Ključne besede: inductance-to-frequency converter, hysteresis, automated measurement, sensor switching method, inductance, quartz crystal, temperature compensation
Objavljeno v DKUM: 30.06.2016; Ogledov: 2085; Prenosov: 465
Celotno besedilo (3,93 MB)
Gradivo ima več datotek! Več...

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: 248
Celotno besedilo (23,37 MB)