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Dive into the research topics where Woongkul Lee is active.

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Featured researches published by Woongkul Lee.


IEEE Transactions on Industry Applications | 2017

Comparison Between Output CM Chokes for SiC Drive Operating at 20- and 200-kHz Switching Frequencies

Di Han; Casey T. Morris; Woongkul Lee; Bulent Sarlioglu

The adoption of silicon carbide (SiC) MOSFETs in variable speed drives (VSDs) makes it possible to increase the inverter switching frequency up to several hundred kilohertz without incurring excessive inverter loss. As a result, the harmonic currents and related losses in the machine can be significantly reduced, and the dynamic performance of motor will also be improved. However, the high switching frequency will increase the common mode (CM) electromagnetic interference (EMI) emission of the drive system presenting new challenges on CM choke design. In the literature, chokes designed for VSDs operating above 100 kHz are rarely found. Hence, this paper presents a case study on the output CM chokes for a SiC-based VSD switching at 20 and 200 kHz. A comprehensive comparison is made between the chokes for two switching frequencies regarding design, sizing, and performance, through both calculation and experiments. The results show that the CM choke designed for 200 kHz switching frequency is significantly larger and heavier than the 20 kHz choke, due to the higher inductance value required to meet the EMI limit and the lower permeability of the core material. Meanwhile, the 200 kHz choke is also less effective in noise attenuation as a result of the larger winding capacitance compared with the 20 kHz choke.


ieee transportation electrification conference and expo | 2014

Investigating the Influence of Interconnection Parasitic Inductance on the Performance of SiC Based DC-DC Converters in Hybrid Vehicles

Di Han; Woongkul Lee; Jukkrit Noppakunkajorn; Bulent Sarlioglu

Silicon carbide (SiC) based devices are known to outperform Si devices in many aspects, such as lower power dissipation, higher operating temperatures, and higher switching frequencies. SiC devices will benefit hybrid vehicles when applied into the DC-DC converters and inverters as part of the electrical power conversion needed to drive the powertrain. Nevertheless, SiC devices can suffer from oscillations as a result of the underdamped response to an RLC circuit composed of device output capacitance, parasitic inductance, and on-state resistance. This paper aims at investigating the influence of the interconnection parasitic inductance on the performance of SiC-based DC-DC converter in hybrid vehicles.


applied power electronics conference | 2016

Determination of CM choke parameters for SiC MOSFET motor drive based on simple measurements and frequency domain modeling

Di Han; Casey T. Morris; Woongkul Lee; Bulent Sarlioglu

The adoption of silicon carbide (SiC) MOSFETs in variable speed motor drives makes it possible to increase the inverter switching frequency up to several hundred kilohertz without incurring excessive inverter loss. As a result, the harmonic currents and related losses in the machine can be significantly reduced, and the dynamic performance of motor will also be improved. However, the increased switching frequency of SiC drives will increase the ground leakage current in the common mode (CM) path, presenting new challenges on CM choke design. This paper aims at understanding the CM choke design under this new circumstance. First, a simple and accurate frequency domain CM circuit modeling approach suitable for SiC motor drives is proposed and subsequently verified through experimental tests. Based on the model, required choke parameters are then determined through analytical calculation. Through comparative analysis, the impact of increased switching frequency on CM choke design is studied.


international conference on performance engineering | 2015

Minimizing switching losses in high switching frequency GaN-based synchronous buck converter with zero-voltage resonant-transition switching

Woongkul Lee; Di Han; Casey T. Morris; Bulent Sarlioglu

GaN power switching devices are promising candidates for high switching frequency and high efficiency operations due to their lower on-resistance and faster switching capabilities compared to conventional silicon power devices. As the switching frequency increases up to the MHz-level, soft switching plays an important role to further minimize the switching losses and improve the efficiency. In this paper, a GaN-based synchronous buck converter operating with zero-voltage resonant-transition (ZVRT) switching in synchronous conduction mode is proposed. The ZVRT switching converter offers a favorable trade-off between switching and conduction losses especially in GaN-based DC-DC converters. The efficiency of the ZVRT switching converter providing 20 W output power from 28 V input voltage improves up to 7% at 3 MHz switching frequency.


conference of the industrial electronics society | 2014

GaN-based single phase brushless DC motor drive for high-speed applications

Woongkul Lee; Di Han; Bulent Sarlioglu

It is a well-known fact that wide-bandgap (WBG) materials such as gallium nitride (GaN) and silicon carbide (SiC) have superior characteristics compared to silicon (Si) in power electronics and motor drive applications. Performance of a single-phase brushless high-speed DC motor can be improved by using GaN-based drive since it requires high frequency operation and low conduction and switching losses. This paper discusses the implementation of GaN devices to drive a single-phase brushless DC motor. Control strategies and simulation analysis are presented. Comparison is carried out between GaN-based and Si-based brushless DC motor drive systems and the potential benefits of GaN-based drive system are quantified from the efficiency and loss perspective.


ieee transportation electrification conference and expo | 2016

Reactive power control of grid-connected inverter in vehicle-to-grid application for voltage regulation

Wooyoung Choi; Woongkul Lee; Bulent Sarlioglu

Vehicle-to-grid is a promising concept, which has a potential to provide ancillary services to the power grid such as peak load reduction, spinning and non-spinning reserve, and voltage and frequency regulation. This paper investigates the control method of a grid-connected inverter in vehicle to grid application for voltage regulation through reactive power control. The control technique is to maintain the point of common coupling voltage at a nominal value when there is sag or swell on grid voltage. The required power is mathematically derived as a function of the balanced sag or swell factor and phase angle of compensated voltage. The proposed control technique is simulated using MATLAB Simulink and Simpower tools.


applied power electronics conference | 2016

Effect of grid inductance on grid current quality of parallel grid-connected inverter system with output LCL filter and closed-loop control

Wooyoung Choi; Woongkul Lee; Bulent Sarlioglu

Grid-connected inverters (GCIs) are power electronics interfaces to connect distributed energy resources into the grid. In order to improve the performance of distributed energy resources as well as maintain the high power quality of the grid, it is important to understand the characteristic of GCIs with appropriate controllers depending on its applications. This paper presents a study on the effect of grid inductance on quality of the grid current when there are multiple parallel-connected inverters to the grid. The model includes three-phase two-level voltage source inverters, output LCL filter, the grid, and voltage-oriented PI controller with a power controller. Parallel GCI systems are mathematically modeled. Frequency responses of grid current are investigated according to different grid inductances. A parallel grid-connected inverter system is simulated using MATLAB Simulink in order to present the effect of grid inductance on grid current and power quality.


ieee transportation electrification conference and expo | 2017

Reviews on grid-connected inverter, utility-scaled battery energy storage system, and vehicle-to-grid application - challenges and opportunities

Wooyoung Choi; Yujiang Wu; Di Han; Joseph Gorman; Pablo Castro Palavicino; Woongkul Lee; Bulent Sarlioglu

The purpose of this paper is to review three emerging technologies for grid-connected distributed energy resource in the power system: grid-connected inverters (GCIs), utility-scaled battery energy storage systems (BESSs), and vehicle-to-grid (V2G) application. The overview of GCIs focuses on topologies and functions. Different functions of utility-scaled BESS are introduced and a comprehensive review is provided for currently operating BESSs that are interconnected at the distribution level. Possible grid support functions of utility-scaled BESS are presented. This paper also presents the current electro-chemical based ESSs in the U.S. with different grid support functions. The V2G technology is introduced focusing on benefits for grid support. The state-of-the-art of GCI, BESS, and V2G technologies presents many opportunities and challenges that need to be addressed in the future.


ieee transactions on transportation electrification | 2017

A Case Study on Common Mode Electromagnetic Interference Characteristics of GaN HEMT and Si MOSFET Power Converters for EV/HEVs

Di Han; Casey T. Morris; Woongkul Lee; Bulent Sarlioglu

Wide bandgap semiconductors, such as gallium nitride (GaN)-based power devices have become increasingly popular in the automotive industry due to their low on-state resistance and fast switching capabilities. These devices are sought to replace silicon (Si) devices in power electronics converters for vehicular applications. GaN devices dissipate less energy during each switching event, thus, GaN converter designers can significantly increase the switching frequency without increasing switching losses, relative to Si converters. However, one item of concern is that the high


ieee transportation electrification conference and expo | 2016

Three-phase common mode inductor design and size minimization

Di Han; Casey T. Morris; Woongkul Lee; Bulent Sarlioglu

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Bulent Sarlioglu

University of Wisconsin-Madison

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Di Han

University of Wisconsin-Madison

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Wooyoung Choi

University of Wisconsin-Madison

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Silong Li

University of Wisconsin-Madison

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Casey T. Morris

University of Wisconsin-Madison

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Dheeraj Bobba

University of Wisconsin-Madison

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Erik Schubert

University of Wisconsin-Madison

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Pablo Castro Palavicino

University of Wisconsin-Madison

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Yingjie Li

University of Wisconsin-Madison

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Yujiang Wu

University of Wisconsin-Madison

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