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Drazen Dujic

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Publications associées (209)

Comprehensive Comparison of Modular Multilevel Converter Internal Energy Balancing Methods

Drazen Dujic, Stefan Milovanovic

Stacking of the floating structures, known as submodules or cells, provides the modular multilevel converter with theoretically unlimited voltage scalability. However, such a convenience comes at a price of increased control complexity, especially in the d ...

2021

Improved Natural-Air-Convection-Cooling Formulas for Medium Frequency Transformer Design Optimization

Marko Mogorovic, Drazen Dujic, Jonas Piet K Le Roy

This paper provides accurate analytic models for a computationally efficient estimation of the natural con- vection cooling coefficients for typical geometries, such as those encountered in transformers. Proper thermal coordination is an essential step of ...

2021

Hardware-in-the-Loop Characterization of Source-Affected Output Characteristics of Cascaded H-Bridge Converter

Marko Petkovic, Drazen Dujic

Recent trends in power system design such as an increasing share of renewable energy sources and integration of power electronics equipment for medium voltage applications are creating different subsystem interactions that require proper investigation, und ...

2021

Turbine mode start-up simulation of a FSFC variable speed pump-turbine prototype - Part I: 1D simulation

François Avellan, Antoine Béguin, Sébastien Alligné, Drazen Dujic

Variable speed hydroelectric units equipped with full size frequency converter (FSFC) offer high operational flexibility enabling fast operating point transitions which increase grid regulation capacities. The XFLEX HYDRO H2020 European research project ai ...

IOP PUBLISHING LTD2021

Design and Characterization of PCB Spiral Coils for Inductive Power Transfer in Medium Voltage Applications

Drazen Dujic, Xiaotong Du, Chengmin Li

Coil design and operating frequency are key factors impacting the efficiency of inductive power transfer system. This paper presents the modeling of PCB spiral coils, design optimization and analysis on coil geometry and operating frequency for medium volt ...

2021

Robust and Cost Effective Synchronization Scheme for a Multicell Grid Emulator

Drazen Dujic, Min Luo, Nicolai Hildebrandt

Steadily increasing requirements for grid connected converters, their growing unit power and output voltage call for flexible high-power medium-voltage grid emulators. Four-quadrant cascaded H-bridge topology features high output voltage resolution and hig ...

2021

Current Limiting in Overload Conditions of an LLC-Converter-Based DC Transformer

Drazen Dujic, Jakub Kucka

The dc transformers based on an LLC converter operated in open loop near resonant frequency have several crucial advantages compared to other topologies. These advantages are the stiff voltage ratio with a natural power flow, the dc grid isolation via medi ...

2021

Solid-State Technologies for Flexible and Efficient Marine DC Microgrids

Drazen Dujic, Gabriele Ulissi, Seongil Kim, Jakub Kucka

2021

Breakerless Protection for Voltage Source Converter-Based Marine DC Power Supply Systems

Drazen Dujic, Seongil Kim

DC power supply systems utilising voltage source converters offer several advantages compared with their counterparts in marine low-voltage DC power distribution networks. In case of a two-level voltage source converter fed by a synchronous generator which ...

IEEE2021

High Frequency Operation of Series-Connected IGCTs for Resonant Converters

Drazen Dujic, Gabriele Ulissi

Series connected IGCTs find application in hard-switched commercial power converters at the MW power levels. Expanding the application of these devices to medium voltage dc-dc resonant converters is of great interest due to the IGCTs low conduction losses. ...

2021

Hybrid Modular Multilevel Converter for Variable DC Link Voltage Operation

Drazen Dujic, Miodrag Basic

2021

An IGCT Gate Unit for Zero-Voltage-Switching Resonant DC Transformer Applications

Drazen Dujic, Jakub Kucka

Recently, IGCTs have shown a great potential for the soft-switching dc transformer applications based on LLC resonant converter. The zero-voltage switching that is present in this converter topology enables an operation of IGCTs without clamping circuit an ...

2021

Equal Loss Distribution in Duty-Cycle Controlled H-Bridge LLC Resonant Converters

Drazen Dujic, Jakub Kucka

The duty-cycle control is a popular option for current limiting in LLC resonant converters. Such current limiting is required to protect the converter either during the start-up or during an overload. Although this method proved to be effective, the switch ...

2021

Thermally-Compensated Magnetic Core Loss Model for Time-Domain Simulations of Electrical Circuits

Drazen Dujic, Min Luo, Nikolina Djekanovic

This paper introduces a thermally-compensated magnetic hysteresis model, capable of accurately determining core losses of ferrite materials while accounting for core temperature variations. The employed model is based on permeance-capacitance analogy and i ...

2021

Hardware-in-the-Loop Modeling of an Actively Fed MVDC Railway Systems of the Future

Drazen Dujic, Stefan Milovanovic

This paper presents an averaged real-time model of an arbitrary size MVDC railway system. In contrast to references already available in the literature, focusing mainly on specific parts of such a railway network (e.g. power converter installed in a locomo ...

2021

Distributed Real-Time Model of the M3C for HIL Systems Using Small-Scale Simulators

Philippe Alexandre Bontemps, Drazen Dujic, Stefan Milovanovic

Hardware-in-the-loop systems are an essential tool to verify controllers and deployed control algorithms in a risk-free environment. The inaccessibility of the converters used in applications such as pumped hydro storage power plants due to their high rati ...

2021

Nodal Impedance Assessment in DC Power Distribution Networks

Drazen Dujic, Renan Pillon Barcelos

IEEE2021

Flexible and Efficient MMC Digital Twin Realized With Small-Scale Real-Time Simulators

Drazen Dujic, Stefan Milovanovic, Milan Utvic, Ignacio Alejandro Polanco Lobos

2021

Turbine mode start-up simulation of a variable speed Francis pump-turbine prototype - Part II: 3-D unsteady CFD and FEM

François Avellan, Drazen Dujic

The Z'Mutt pumping station, part of the Grande Dixence hydroelectric scheme, is one of the demonstrators of the XFLEX HYDRO project. A 5 MW reversible pump-turbine prototype equipped with a full-size frequency converter (FSFC) is used to investigate dynami ...

IOP PUBLISHING LTD2021

Protection Coordination for Reliable Marine DC Power Distribution Networks

Drazen Dujic, Gabriele Ulissi, Seongil Kim

This paper presents demonstration of a protection scheme integrated into marine DC power distribution networks to investigate the coordination between each protection action. The integrated protection scheme is based on three different time-frame protectio ...

2020

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