Chinese Journal of Electrical Engineering ›› 2020, Vol. 6 ›› Issue (4): 53-62.doi: 10.23919/CJEE.2020.000030

Special Issue: Special Issue on Switched-Capacitor Circuits and Partial Processing Techniques

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Fast Online Diagnosis of Open-circuit Switching Faults in Flying Capacitor Multilevel Inverters

Majid T. Fard1, Waqar A. Khan2, Jiangbiao He1,*, Nathan Weise2, Mostafa Abarzadeh2   

  1. 1. Department of Electrical and Computer Engineering, University of Kentucky, Lexington, KY 40506, USA;
    2. Department of Electrical and Computer Engineering, Marquette University, Milwaukee, WI 53233, USA
  • Received:2020-08-12 Revised:2020-09-24 Accepted:2020-10-23 Online:2020-12-25 Published:2021-01-15
  • Contact: *E-mail: jiangbiao@ieee.org
  • About author:Majid T. Fard (S'19) received the B.S. and M.S. degrees in electrical engineering with an emphasis on power energy conversion and renewable energies from the University of Tabriz, Iran in 2013 and 2016, respectively. He is currently working toward the Ph.D. degree in electrical engineering at the University of Kentucky, KY, USA. He previously worked in industry, as an R&D engineer and project manager at the IKCO (EKS) automotive company in Iran. His research interests include high-power high-frequency propulsion drives for more-electric aircraft systems, fault-tolerant operation of power converters for safety-critical applications, and renewable energy power conversion.
    Waqar A. Khan (S'18) received the B.S. degree in electrical engineering from University of Engineering and Technology, Taxila, Pakistan and an M.S. degree (with Hons.) in electrical engineering from Aalto University, Finland in 2016. He began pursuing his Ph.D. at Marquette University, Milwaukee, WI in 2018. His research interests include wide band gap devices, design/modulation techniques of multilevel power converters and digital control of grid-connected power converters and motor drives.
    Jiangbiao He (S'08-M'15-SM'16) is an assistant professor in electric power area with the Department of Electrical and Computer Engineering, University of Kentucky, USA. He previously worked in industry, most recently as a lead engineer with GE Global Research, Niskayuna, New York. He also worked at Eaton Corporation and Rockwell Automation before he joined GE in 2015. He received the Ph.D. degree in electrical engineering from Marquette University, WI, USA. His research interests include high-performance propulsion drives for electric transportation, renewable energies and energy storage, and fault-tolerant power conversion systems for safety-critical applications. He has authored more than 90 technical papers and 10 U.S. patents in electric power area. Dr. He has served as an editor or Associate Editor for several IEEE Transactions journals. He also served in the organizing committees for various IEEE international conferences (IEMDC-2017, ECCE-2018, ITEC-2019, etc.), and has been an active member of multiple IEEE standards working groups. He is a recipient of the 2019 AWS Outstanding Young Member Achievement Award from IEEE Industry Applications Society.
    Nathan Weise (M'08-SM'18) received the B.S. degree in computer engineering, the M.S. degree in electrical engineering with an emphasis on wireless, and the Ph.D. degree in electrical engineering with an emphasis on power from the University of Minnesota, Minneapolis, MN, USA, in 2005, 2007, and 2011, respectively. He was an electrical engineer with Cummins Power Generation, Minneapolis, MN, USA, and General Electric Global Research, Niskayuna, NY, USA. He joined Marquette University, Milwaukee, WI, USA, as an assistant professor in 2014. His current research interests include power electronics, power converters, wave energy conversion, electrification of transportation, all-electric aircraft, fault tolerance, control of renewable energy sources, digital control of power electronics, and wide bandgap devices.
    Mostafa Abarzadeh (S'15-M'16-SM'19) received the B.S., M.S., and Ph.D. (All with Hons.) degrees in electrical engineering from Sahand University of Technology (SUT), Tabriz, Iran, in 2008, 2011, and 2016, respectively.He was a visiting Ph.D. researcher with Aalborg University, Denmark, in 2015. From 2016 to 2017, he was an assistant professor with the Electrical Engineering Faculty of SUT. From 2017 to 2019, he was a postdoctoral research fellow with the Canada Research Chair in Electric Energy Conversion and Power Electronics, École de Technologie Supérieure (ÉTS), University of Quebec, Canada. Currently, he is a postdoctoral research associate with the EMPOWER Lab., Marquette University, Milwaukee, WI, US. He has authored or co-authored over 40 journal and conference papers and book chapters and holds 6 patents. He has been a principle investigator (PI) of industrial and research grants in the field of the industrial electronics. He has implemented more than 25 industrial and research projects in the field of the industrial electronics and he has transferred know-how technologies to industry for more than 10 industrial and research projects. Since 2006, he has been a member of the Iran's National Elites Foundation. He was a recipient of the Best Poster Presentation Award from the IEEE Energy Conversion Congress and Exposition (ECCE) in 2015. His current research interests include high performance high power density power electronic converters based on wide band gap (WBG) devices, as well as topology, modeling, control and modulation of power electronic converters, hybrid multilevel inverters, and applications of power electronics in renewable energy conversion, transportation electrification, power grid, and variable-speed motor drives.

Abstract: Flying capacitor multilevel (FCML) inverter is an attractive power converter topology which provides high-quality staircase output voltage waveforms by cascading flying capacitor cells. However, the large number of semiconductor devices utilized in the FCML inverters degrades the hardware reliability, which may constrain such converters from being applied in safety-critical applications. Targeting at open-circuit switching faults, a fast online fault diagnostic method for FCML inverters is presented. Conventional phase-shifted PWM (PSPWM), which can naturally balance the voltage across flying capacitors, is used as the modulation method in this work. Hence, to retain the simplicity feature of the PSPWM, the proposed diagnostic method is developed so that it does not require any voltage measurements of flying capacitors. Only the output AC voltage and current data along with the switching PWM signals from the microcontroller are needed to detect an open-circuit switching fault, and all such sensory data is typically available in the inverter, requiring no additional sensors or hardware for the implementation of this diagnostic method. The detection process takes 5% of the fundamental period of the inverter output signals to diagnose the faulty switch. Simulation and experimental results are presented to verify the effectiveness of the proposed diagnostic method.

Key words: Open-circuit, fault diagnosis, flying capacitor, multilevel inverter, wide bandgap devices, PSPWM