2016. Ph.D. in Electrical Engineering, Aalborg University, DENMARK
2013. M.S. in Electrical and Electronic Engineering, Ajou University, KOREA
2011. B.S. in Electrical and Electronic Engineering, Ajou University, KOREA

Associate Professor, Seoul National University of Science and Technology
Postdoctoral Researcher, Aalborg University
Partner Researcher, Grundfos Holding A/S

Reliability of Power Electronic Components and Systems
Power Electronics Converters - Design and Control
Renewable Energy Generation Systems (Solar PV, Wind)
Multilevel Converters
Electric Machine Drives (Traction Applications)

전력전자
전자기학
기초전기전자실험

[40] T. Ryu and *U. M. Choi, “Reliability-Oriented Application Method of Discontinuous PWM for Single-Phase Five-Level T-type NPC Inverter,” IEEE Transactions on Power Electronics, in press.
[39] T. Ryu and *U. M. Choi, “Discontinuous PWM Strategy for Reliability and Efficiency Improvement of Single-Phase Five-Level T-type Inverter,” IEEE Transactions on Industrial Electronics, vol.71, no. 3, pp. 2567-2577, Mar. 2024.
[38] U. M. Choi and J. H. Park, “Development and Reliability Assessment of Si and SiC Power Devices based Solid-State Transformer for Urban Railway Vehicle,” IEEE Transactions on Transportation Electrification, vol.9, no. 2, pp. 2744-2753, June 2023.
[37] Y. Ko, T. Ryu, and *U. M. Choi, “Active thermal control for reliability improvement in photovoltaic single-phase T-type NPC inverters,” Journal of Power Electronics, vol.23, no. 5, pp. 850-859, May 2023.
[36] T. Ryu, and *U. M. Choi, “Reliability-Oriented Optimal DPWM Strategy for Single-Phase Five-Level T-type Inverter in PV Systems,” IEEE Journal of Emerging and Selected Topics in Power Electronics, vol.11, no. 2, pp. 2227-2235, Apr. 2023.
[35] T. Ryu, *U. M. Choi, I. Vernica, and F. Blaabjerg, “Effect of thermal loading definitions on the mission profile-based reliability evaluation of power devices in PV inverters,” Microelectronics Reliability, vol. 138, Nov. 2022, 114650.
[34] U. M. Choi and J. S. Lee, “Single-Phase Five-Level IT-Type NPC Inverter with Improved Efficiency and Reliability in Photovoltaic Systems,” IEEE Journal of Emerging and Selected Topics in Power Electronics, vol.10, no. 5, pp. 5226-5239, Oct. 2022.
[33] J. S. Lee and *U. M. Choi, “Velocity Profile based Evaluation and Improvements of Lifetime of Power Devices in Railway Propulsion Inverters,” IEEE Journal of Emerging and Selected Topics in Power Electronics, vol.10, no. 2, pp. 1384-1394, Apr. 2022.
[32] U. M. Choi and T. Ryu, “Comparative Evaluation of Efficiency and Reliability of Single-Phase Five-Level NPC Inverters for Photovoltaic Systems,” IEEE Access, vol. 9, pp. 120638-120651, 2021.
[31] U. M. Choi, “Study on Effect of Installation Location on Lifetime of PV Inverter and DC-to-AC Ratio,” IEEE Access, vol. 8, pp. 86003-86011, 2020.
[30] U. M. Choi, I. Vernica, D. Zhou, and F. Blaabjerg, “Comparative evaluation of reliability assessment methods of power modules in motor drive inverter,” Microelectronics Reliability, vols. 114, 113730, Nov. 2020.
[29] I. Vernica, *U. M. Choi, H. Wang, and F. Blaabjerg, “Wear-out failure of an IGBT module in motor drives due to uneven thermal impedance of power semiconductor devices,” Microelectronics Reliability, vols. 114, 113800, Nov. 2020.
[28] U. M. Choi and J. S. Lee, “Comparative Evaluation of Lifetime of Three-Level Inverters in Grid-Connected Photovoltaic Systems,” Energies, vol. 13, no. 5, 2020.
[27] J. S. Lee and U. M. Choi, “Comparison of Heat-Pipe Cooling System Design Processes in Railway Propulsion Inverter Considering Power Module Reliability,” Energies, vol. 12, no. 24, 2019.
[26] U. M. Choi, S. Jørgensen, and F. Blaabjerg, “Impact of Cooling System Capacity on Lifetime of Power Module in Adjustable Speed Drives,” IEEE Journal of Emerging and Selected Topics in Power Electronics, vol. 7, no. 3, pp. 1768-1776, Sept. 2019.
[25] U. M. Choi, J. S. Lee, and F. Blaabjerg, “Effect of Power Cycling Test Condition and Test Strategy on Lifetime Estimation of Power Modules in Power Electronic Systems,” Microelectronics Reliability, vols. 100-101, 113460, Sept. 2019.
[24] U. M. Choi, I. Vernica, and F. Blaabjerg, “Effect of Asymmetric Layout of IGBT Modules on Reliability of Motor Drive Inverters,” IEEE Transactions on Power Electronics, vol. 34, no. 2, pp. 1765-1772. Feb. 2019.
[23] K. Ma, U. M. Choi, and F. Blaabjerg, “Prediction and Validation of Cumulative Distribution Function for Power Semiconductor Devices with Mission Profiles in Motor Drive Application, IEEE Transactions on Power Electronics, vol. 33, no. 11, pp. 9843-9853, Nov. 2018.
[22] U. M. Choi, S. Jørgensen, F. Iannuzzo, and F. Blaabjerg, "Power cycling test of transfer molded IGBT modules by advanced power cycler under different junction temperature swings," Microelectronics Reliability, vols. 88-90, pp. 788-794. Sep. 2018.
[21] U. M. Choi, and F. Blaabjerg, “Separation of Wear-out Failure Modes of IGBT Modules in Grid-Connected Inverter Systems,” IEEE Transactions on Power Electronics, vol. 33, no. 7, pp. 6217-6223. July 2018.
[20] U. M. Choi, K. Ma and F. Blaabjerg, “Validation of Lifetime Prediction of IGBT Modules Based on Linear Damage Accumulation by Means of Superimposed Power Cycling Tests,” IEEE Transaction on Industrial Electronics, vol. 65, no. 4, pp. 3520-3529. Apr. 2018.
[19] U. M. Choi, F. Blaabjerg, and S. Jørgensen, “Power Cycling Test Methods for Reliability Assessment of Power Device Modules in respect to Temperature Stress,” IEEE Transactions on Power Electronics, vol. 33, no. 3, pp. 2531-2551. Mar. 2018.
[18] U. M. Choi, F. Blaabjerg, S. Munk-Nielsen, S. Jørgensen and B. Rannestad, “Reliability Improvement of Power Converters by Means of Condition Monitoring of IGBT Modules,” IEEE Transactions on Power Electronics, vol. 32, no. 10, pp. 7990-7997. Oct. 2017.
[17] U. M. Choi, F. Blaabjerg and F. Iannuzzo, “Advanced Power Cycler with Intelligent Monitoring Strategy of IGBT Module Under Test,” Microelectronics Reliability, vols. 76-77, pp. 522-526, Sep. 2017.
[16] U. M. Choi, F. Blaabjerg, and S. Jørgensen, “Study on Effect of Junction Temperature Swing Duration on Lifetime of Transfer Molded Power IGBT Modules,” IEEE Transactions on Power Electronics, vol. 32, no. 8, pp. 7990-7997. Aug. 2017.
[15] U. M. Choi, S. Jørgensen and F. Blaabjerg, “Advanced Accelerated Power Cycling Test for Reliability Investigation of Power Device Modules,” IEEE Transactions on Power Electronics, vol. 31, no. 12, pp. 8371-8386. Dec. 2016.
[14] U. M. Choi, J. S. Lee, F. Blaabjerg, and K. B. Lee, “Open-Circuit Fault Diagnosis and Fault-Tolerant Control for a Grid-Connected NPC Inverter,” IEEE Transactions on Power Electronics, vol. 31, no. 10, pp. 7234-7247. Oct. 2016.
[13] U. M. Choi, F. Blaabjerg, S. Jorgensen, F. Iannuzzo, H. Wang, C. Uhrenfeldt, and S. Munk-Nielsen, “Power cycling test and failure analysis of molded Intelligent Power IGBT Module under different temperature swing durations.” Microelectronics Reliability, vol. 64, pp. 403-408, Sep. 2016.
[12] J. S. Lee, U. M. Choi, and K. B. Lee, “Comparison of Tolerance Controls for Open-Switch Fault in a Grid-Connected T-Type Rectifier,” IEEE Transactions on Power Electronics, vol. 30, no. 10, pp. 5810-5820, Oct. 2015.
[11] U. M. Choi, F. Blaabjerg, F. Iannuzzo, and S. Jørgensen, “Junction temperature estimation method for a 600 V, 30A IGBT module during converter operation,” Microelectronics Reliability, vol. 55, no. 9-10, pp. 2022-2026, Aug.-Sep. 2015.
[10] U. M. Choi, F. Blaabjerg, and K. B. Lee, “Reliability Improvement of a T-Type Three-Level Inverter With Fault-Tolerant Control Strategy,” IEEE Transactions on Power Electronics, vol. 30, no. 5, pp. 2660-2673. May 2015.
[9] U. M. Choi, F. Blaabjerg, and K. B. Lee, “Study and Handling Methods of Power IGBT Module Failures in Power Electronic Converter Systems,” IEEE Transactions on Power Electronics, vol. 30, no. 5, pp. 2517-2533. May 2015.
[8] U. M. Choi, F. Blaabjerg, and K. B. Lee, “Control Strategy of Two Capacitor Voltages for Separate MPPTs in Photovoltaic Systems Using Neutral-Point-Clamped Inverters,” IEEE Transactions on Industry Applications, vol. 51, no. 4, pp. 3295-3303. July-Aug. 2015.
[7] U. M. Choi, F. Blaabjerg, and K. B. Lee, “Method to Minimize the Low-Frequency Neutral-Point Voltage Oscillations With Time-Offset Injection for Neutral-Point-Clamped Inverters,” IEEE Transactions on Industry Applications, vol. 51, no. 2, pp. 1678-1691. Mar.-Apr. 2015.
[6] U. M. Choi, K. B. Lee, and, F. Blaabjerg “Diagnosis and Tolerant Strategy of an Open-Switch Fault for T-Type Three-Level Inverter Systems,” IEEE Transactions on Industry Applications, vol. 50, no. 1, pp. 495-508. Jan.-Feb. 2014.
[5] U. M. Choi, J. S. Lee and K. B. Lee, “New Modulation Strategy to Balance the Neutral-Point Voltage for Three-Level Neutral-Clamped Inverter Systems,” IEEE Transactions on Energy Conversion, vol. 29, no. 1, pp. 91-100. Mar. 2014.
[4] U. M. Choi, H. H. Lee and K. B. Lee, “Simple Neutral-Point Voltage Control for Three-Level Inverters Using a Discontinuous Pulse Width Modulation,” IEEE Transactions on Energy Conversion, vol. 28, no. 2, pp. 434-443. Jun. 2013.
[3] U. M. Choi, and K. B. Lee, “Space vector modulation strategy for neutral-point voltage balancing in three-level inverter systems,” IET Power Electronics, vol. 6, no. 7, pp. 1390-1398. Aug. 2013.
[2] U. M. Choi, and K. B. Lee, “Neutral-Point Voltage Balancing Method for Three-Level Inverter Systems with a Time-Offset Estimation Scheme,” Journal of Power Electronics, vol. 13, no. 2, pp. 243-249. Mar. 2013.
[1] U. M Choi, H. G. Jeong, K. B. Lee, and F. Blaabjerg, “Method for Detecting an Open-Switch Fault in a Grid-Connected NPC Inverter System,” IEEE Transactions on Power Electronics, vol. 27, no. 6, pp. 2726-2739, June 2012.

[25] T. Lee and U. M. Choi, “Discontinuous PWM for Improving Reliability and Efficiency of Single-Phase Five-Level T-type NPC Inverter with reduced Harmonic Distortion,” in Proc. of EPE-ECCE Europe, Sept. 2023.
[24] J. H. Lee and U. M. Choi, “Discontinuous Pulse Width Modulation for Improving Reliability of NPC Inverter operated at High Modulation Index” in Proc. of ECCE Europe, Sept. 2023.
[23] T. Lee and U. M. Choi, “Influence of Different PWM Methods on Thermal Loadings of Power Devices and DC-link Capacitors of Single-Phase Five-Level T-type NPC Inverter,” in Proc. of ICPE-ECCE Asia, May 2023.
[22] J. H. Lee and U. M. Choi, “Pulse Width Modulation Method for Reliability Improvement of DC-link Capacitors and Power Devices of NPC Inverter” in Proc. of ICPE-ECCE Asia, May 2023.
[21] J. H. Park, U. M. Choi, and J. S. Lee, “Sinusoidal Third Harmonic Voltage Injection PWM Method for Applying the LCL Filter to Vienna Rectifier,” in Proc. of ICPE-ECCE Asia, May 2019.
[20] U. M. Choi, and F. Blaabjerg, “Effect of Asymmetric Layout of IGBT Modules on Reliability of Power Inverters in Motor Drive System,” in Proc. of AEPC 2018, Mar. 2018.
[19] U. M. Choi, and F. Blaabjerg, “Real-time condition monitoring of IGBT modules in PV inverter systems,” in Proc. of CIPS 2018, Mar. 2018.
[18] U. M. Choi, and F. Blaabjerg, “Asymmetric Power Device Rating Selection for Even Temperature Distribution in NPC Inverter,” in Proc. of ECCE 2017, pp. 4196-4201, Oct. 2017.
[17] K. Ma, U. M. Choi and F. Blaabjerg, “Reliability Metrics Extraction for Power Electronics Converter Stressed by Thermal Cycles,” in Proc. of ECCE 2017, pp. 3838-3842, Oct. 2017.
[16] U. M. Choi, K. Ma and F. Blaabjerg, “Lifetime Prediction of IGBT Modules based on Linear Damage Accumulation,” in Proc. of APEC 2017, pp. 2276-2281, Mar. 2017.
[15] K. Ma, U. M. Choi, and F. Blaabjerg, “Impacts of Ripple Current to the Loading and Lifetime of Power Semiconductor Device,” in Proc. of APEC 2017, pp. 2305-2311, Mar. 2017.
[14] U. M. Choi, F. Blaabjerg, and S. Jørgensen, “Effect of Junction Temperature Swing Durations on a Lifetime of a Transfer Molded IGBT Module,” in Proc. of ECCE 2016, Sep. 2016.
[13] U. M. Choi, F. Blaabjerg, S. Munk-Nielsen, S. Jørgensen and B. Rannestad, “Condition Monitoring of IGBT Module for Reliability Improvement of Power Converters,” in Proc. of ITEC Asia-Pacific 2016, pp. 602-607. June 2016.
[12] U. M. Choi, and F. Blaabjerg, “A novel active T-type three-level converter with open-circuit fault-tolerant control,” in Proc. of ECCE 2015, pp. 4765-4772. Sep. 2015.
[11] U. M. Choi, I. Trintis, F. Blaabjerg, S. Jørgensen, and M. L. Svarre, “Advanced Power Cycling Test for Power Module with On-line On-state VCE Measurement,” in Proc. of APEC 2015, pp. 2919-2924, Mar. 2015.
[10] U. M. Choi, F. Blaabjerg, J. S. Lee, and K. B. Lee, “Open-circuit fault diagnosis for a grid-connected NPC inverter with unity Power Factor,” in Proc. of APEC 2015, pp. 213-220, Mar. 2015.
[9] U. M. Choi, and F. Blaabjerg, “Junction temperature estimation for an advanced active power cycling test,” in Proc. of ICPE-ECCE Asia 2015, pp. 2944-2950, June 2015.
[8] U. M. Choi, F. Blaabjerg, and K. B. Lee, “Independent control strategy of two DC-link voltages for separate MPPTs in transformerless photovoltaic systems using neutral-point-clamped inverters,” in Proc. of APEC 2014, pp. 1718-1724, Mar. 2014.
[7] U. M. Choi, K. B. Lee and F. Blaabjerg, “Method to minimize the low-frequency neutral-point voltage oscillations with time-offset injection for neutral-point-clamped inverters,” in Proc. of ECCE 2013, pp. 4022-4029. Sep. 2013.
[6] U. M. Choi, and K. B. Lee, “Detection method of an open-switch fault and fault-tolerant strategy for a grid-connected T-type three-level inverter system,” in Proc. of ECCE 2012, pp. 4188-4195. Sep. 2012.
[5] U. M. Choi, H. G. Jeong and K. B. Lee, “Method of neutral-point voltage balancing for a grid connected NPC inverter system with time-offset variant estimating,” in Proc. of IPEMC 2012, pp. 499-504. Jun. 2012.
[4] U. M. Choi, K. B. Lee and F. Blaabjerg, “Diagnosis method of an open-switch fault for a grid-connected T-type three-level inverter system,” in Proc. of PEDG 2013, pp. 470-475. Jun. 2012.
[3] U. M. Choi, Kyo-Beum Lee, and Frede Blaabjerg, “Power electronics for renewable energy systems: Wind turbine and photovoltaic systems,” in Proc. of ICRERA 2012, Nov. 2012.
[2] H. H. Lee, U. M. Choi, and Kyo-Beum Lee “Neutral-Point Voltage Control for Grid-connected Three-Level Inverters using a Discontinuous Pulse Width Modulation,” in Proc. of VCCP 2012, pp. 638-642, Oct. 2012.
[1] H. G. Jeong, U. M. Choi, Kyo-Beum Lee, “Control strategies for wind power systems to meet grid code requirements,” in Proc. of IECON 2011, pp. 1250 – 1255, Nov. 2011.

K. B. Lee and U. M. Choi, “Fault and Diagnosis Systems in Power Converters,” in Advanced and Intelligent Control in Power Electronics and Drives, vol. 531, Springer, pp. 143-178, Jan. 2014. ISBN: 978-3-319-03400-3.

[1] (Registration) Apparatus and Method for Fault Diagnosis of Switching Device in Neutral Point Clamped Inverter System, Korean Patent 10-1242250, Mar. 3, 2013.
[2] (Registration) Fault Switch Diagnosis Apparatus and Method of 3 Level T-Type Inverter, Korean Patent 10-1331028, Nov. 13, 2013.
[3] (Registration) Neutral Point Voltage Controller and Method of three-level Inverter Using DPWM, Korean Patent 10-1343428, Dec. 13, 2013.

Senior Member of IEEE (Power Electronics and Industry Applications Societies)
Member of KIPE
IEEE Power Electronics Transactions Second Prize Paper Award, 2017
Associate Editor for the IEEE Open Journal of Power Electronics, (2021 ~ present)
Associate Editor of Journal of Power Electronics (2021. 08 – present)
Associate Editor of CPSS TPEA (2018. 05 – present)
Associate Editor for the Transactions of The Korean Institute of Power Electronics, (2020 ~ present)
Associate Editor of TKIEE (2023. 03 – present)
Guest Associate Editor for Special Issue on “Advancing Power Electronics Reliability: Components, Systems, and Intelligent Operation” in IEEE Transactions on Power Electronics, (2023. 11 – 2024. 03)
Guest Associate Editor for Special Issue on “Failure Mechanism, Fault Characterization and Condition Monitoring of Power Electronics Components and Systems” in IEEE Journal of Emerging and Selected Topics in Power Electronics, (2020. 11 – 2021. 06)
Guest Editor for Special Issue on "Reliability of Power Electronics Systems" in the Energies (2019)
Guest Associate Editor for Special Issue on "Robust and Reliable Power Electronics" in the CPSS Transactions on Power Electronics and Applications (2018)
Technical Adviser of Korea Railroad Research Institute (KRRI) (2018. 08 - 2018. 12, 2019. 08 - 2019. 11)
IEEE ECCE Europe 2023, EPE - Innovation Design Challenge Assessment Committee Member
IEEE ECCE ASIA 2023, ICPE - Session Chair
IEEE ECCE ASIA 2020, IPEMC - Industry Session Committee Co-Chair, Session Chair
IEEE COMPEL 2020 and 2021 - Technical Program Committee Member
ESREF 2018, Committee Member of Track on Renewable Energies Reliability