Publications by Nikolina Djekanovic

Design of a Megawatt-Scale IGCT-Based Medium-Voltage Direct Current Transformer

This paper presents a robust design of a megawattscale medium-voltage (MV) direct current transformer (DCT) that features a bidirectional LLC resonant converter topology. This topology harnesses the inherent ability to control power flow seamlessly between ...

2025

Static and Dynamic Voltage Balancing for an IGCT-Based Resonant DC Transformer

Drazen Dujic, Nikolina Djekanovic, Renan Pillon Barcelos

This paper focuses on the operational characteristics of a medium voltage resonant DC transformer based on a split capacitor IGCT 3L-NPC leg. The study delves into both the dynamic and static balancing aspects of the 3L-NPC when operating in a two-level, 5 ...

2024

Modeling, Optimization and Design of High Power Medium Frequency Transformers

Nikolina Djekanovic

Nowadays, direct current (DC) technology is increasing its presence in alternating current (AC) power systems. This trend is enabled by the progress in energy conversion through semiconductor devices and power electronics. Therefore, it is possible to imag ...

EPFL2023

Modeling and Characterization of Natural-Convection Oil-Based Insulation for Medium Frequency Transformers

Drazen Dujic, Nikolina Djekanovic

Due to its high value of dielectric strength, oil is often used for transformer insulation. Nevertheless, its presence needs to be considered when determining thermal coordination of a converter system, which also includes the challenging modeling of fluid ...

2022

Design Optimization of a MW-level Medium Frequency Transformer

Drazen Dujic, Nikolina Djekanovic

Nowadays, with the increased interest in applications dealing with high-power medium-voltage conversion, there is a strong need to master the design of medium-frequency transformers, which are one of the key components of modern DC transformers. The paper ...

2022

Copper Pipes as Medium Frequency Transformer Windings

Drazen Dujic, Nikolina Djekanovic

2022

Winding Geometry Impact on High Power Medium Frequency Transformer Design

Drazen Dujic, Nikolina Djekanovic

2022

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

Modeling and Integrating Losses of Magnetic Components Into Time-Domain Electric Circuit Simulations

Drazen Dujic, Min Luo, Nikolina Djekanovic

To shorten converter design time and maximize the cost efficiency, advanced design tools are needed. These tools need to be capable of performing simulations in multiple relevant converter domains, such as electric, magnetic, dielectric, and thermal, simul ...

IEEE2020

Integrated Simulation Approach to Loss Calculations of Power Converter Systems

Drazen Dujic, Min Luo, Nikolina Djekanovic

There is a strong need in the power electronics community to have design tools capable of performing simultaneous simulations in different domains, e.g. electric, magnetic, dielectric and thermal. Therefore, this paper presents an approach to the calculati ...

2020