K.M. Smedley

University of California, Irvine, Irvine, California, United States

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Publications (153)205.94 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: The flyback converter is a popular topology for implementing low power and multiple output power supplies. However, the high leakage inductance of the flyback transformer causes high voltage spikes that can damage the main transistor when the switch is turned OFF. Therefore, a turn-off snubber is needed to limit the peak voltage stress. This paper presents the analysis of an energy regenerative snubber using the graphical state-plane technique. The undertaken approach yields a clear-cut design procedure for minimum switch voltage stress. Experimental evaluation of the energy regenerative snubber in comparison with other common snubbers shows that under the same voltage stress the efficiency of energy regenerative snubber has 8% improvement on average over an RCD snubber and 2% improvement over the nondissipative LC snubber.
    IEEE Transactions on Power Electronics 01/2013; 28(11):5323-5332. · 4.08 Impact Factor
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    ABSTRACT: The fault current limiter is considered a viable solution for reducing the fault current in the power line. In the U.S., great effort has been reported in academia and industry in developing such devices. However, demonstrating a fault current limiter in the live power grid is challenging not only technologically but regulatory. This paper reports a joint effort of academia, industry, and utility on prototyping and testing of saturable core high temperature superconductive fault current limiters (HTS FCLs). This device is the first fully operational HTS FCL installed on the commercial medium voltage distribution grid in the U.S.
    IEEE Transactions on Power Delivery 01/2013; 28(3):1271-1279. · 1.52 Impact Factor
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    ABSTRACT: This study is concerned with application of the universal one-cycle control (OCC) technique to implement a three-phase AC electronic load. The proposed AC electronic load is able to emulate complex load behaviour. The study describes the principles of operation and the digital implementation of AC electronics load. To validate the approach, the start-up transient of an induction motor was successfully emulated. Both the simulation and experimental results are reported.
    IET Power Electronics 01/2012; 5(6):827-832. · 1.52 Impact Factor
  • A. Abramovitz, K.M. Smedley
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    ABSTRACT: This paper presents a comparative survey of research activities and emerging technologies of solid-state fault current limiters for power distribution systems.
    IEEE Transactions on Power Electronics 01/2012; 27(6):2770-2782. · 4.08 Impact Factor
  • M.N. Slepchenkov, K.M. Smedley, Jun Wen
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    ABSTRACT: This paper studies the effectiveness of reactive power compensation using a multilevel, hexagram-converter-based STATic COMpensator (STATCOM) with one-cycle control (OCC) for a wind farm with fixed-speed turbines, and the interaction with the power system network. Comparison is made with several common types of multilevel voltage source converters used for STATCOM applications. A new voltage control method based on OCC principles for hexagram-based STATCOMs is proposed and proven by a wind farm power system simulation showing the improvement of voltage variations caused by wind speed changes. The experimental results from tests of a small-scale hexagram converter prototype have verified the proposed converter and control method.
    IEEE Transactions on Industrial Electronics 05/2011; · 5.17 Impact Factor
  • A. Abramovitz, K.M. Smedley
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    ABSTRACT: This paper presents a single-phase power factor corrector based on a tapped-inductor buck-boost converter. This paper suggests simplified models of the power stage under current-mode control and derives small-signal transfer functions of both the current and voltage control loops. Design rules for implementation of the proposed power factor corrector (PFC) are also suggested. The proposed PFC features low dc bus voltage, arbitrary lower than the peak line voltage. The proposed PFC is suitable for applications in computers and communications, where dc isolation can be provided by the downstream dc/dc converters. Simulation and experimental results are also reported and stand in good agreement with theoretical expectations.
    IEEE Transactions on Power Electronics 01/2011; 26(9):2637-2649. · 4.08 Impact Factor
  • Wensheng Song, Xiaoyun Feng, Keyue Smedley
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    ABSTRACT: The configuration of a single-phase three-level neutral point clamped (NPC) converter has been widely applied in high-speed railway electrical traction drive systems. This paper proposes a control and modulation scheme for the single-phase three-level NPC converter. Firstly, an active and reactive current decoupled control scheme in d-q synchronous frame is presented for single-phase three-level NPC converter to reduce the influence between the traction power supply fluctuating voltage and the traction drive system. Secondly, a new space vector PWM (SVPWM) scheme is provided to restrict the voltage step of the input port voltage within half of DC-link voltage. The proposed SVPWM algorithm is designed and analyzed in detail, including sector and basic voltage vector definition, sector identification, basic vector selection, the duty-time calculation and basic vector sequence design. Finally, the effectiveness and advantages of the proposed SVPWM scheme are confirmed by simulation and prototype experimental test.
    01/2011;
  • Jun Wen, Liang Zhou, Keyue Smedley
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    ABSTRACT: The hexagram inverter is composed of six voltage source inverter (VSI) modules interconnected to form a circle via the inductors, which are required to suppress the possible circulating current in the circle. However, the design of the inductors could be challenging, where the inductance should be large enough to suppress the circulating current and small enough to minimize the effect on the output voltage. This paper proposes the utilization of coupled inductors in between any two connected VSI modules instead of stand-alone ones to optimize the hexagram inverter performance. On the basis of this structure, the circulating current can be maximally suppressed by the magnetizing inductance of the coupled inductor, while in the meantime, the output voltage is minimally affected by the leakage inductance. By sharing the magnetic core, the cost and size of the inductors are also reduced. Simulation and a small-scale experiment have been conducted to verify the proposed hexagram inverter structure with the six-winding coupled inductors.
    IEEE Transactions on Industrial Electronics 01/2011; 58(8):3421-3430. · 5.17 Impact Factor
  • Wensheng Song, Keyue Smedley, Xiaoyun Feng
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    ABSTRACT: The configuration of a single-phase AC-DC converter plus a three-phase DC-AC inverter traction system has been widely applied in high speed railway electrical drive systems. If the LC filter is not adopted in the DC-link, the DC-link voltage fluctuation may beat with the motor electric frequency, which could cause an increase in power loss, torque pulsation and audible noise. This paper aims to reduce the beat effect of DC-link voltage fluctuation in the traction drive system, Firstly, the harmonic spectra and beat phenomena are analyzed when square wave modulation is adopted in the high speed region. Secondly, a new extension of One-cycle Control (OCC) is proposed for the inverter-motor drive system in high speed region, which is used for square wave modulation, and the adopted OCC method is designed and analyzed in detail in the paper. Finally, the comparison between the performance of the adopted OCC scheme and the traditional square wave modulation is made, and the effectiveness and advantages of the OCC scheme are confirmed by simulation test.
    01/2011;
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    ABSTRACT: This paper suggests application of the universal One-Cycle Control (OCC) technique to dynamically control a Three-Phase Load Emulator (TPLE). The paper offers a model of the OCC controlled current loop and derives the relationships between the controlled variables. Based on the analysis the required programming equations are derived. To validate the approach, a case study was conducted to experimentally emulate the start-up transient of a realistic Induction Motor. Experimental results are reported.
    01/2011;
  • Pengju Sun, Luowei Zhou, Keyue Ma Smedley
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    ABSTRACT: This paper presents a reconfigurable structure dc-dc converter with wide output range and constant peak power (RS- WOCP). This converter is an extension of the traditional isolated dc-dc converter with two output channels by adding an active switch and two diodes. Theoretical analysis indicates that the pro- posed RS-WOCP converter is able to smoothly reconfigure the output channels in parallel or series to realize wide output voltage range. With this approach, the output voltage is shared equally in the series operating mode and so is the output current in the parallel operating mode. Therefore, the power rating of devices is significantly reduced and the output rectifiers and filters can distribute power losses and thermal stresses. Operating principle, control strategy, modeling, and stability analysis are illustrated in this paper. An experimental prototype of a 200-W DSP-based RS- WOCP converter was built. The experimental results have verified the steady-state performance and fast dynamic response in the whole output voltage range. Comparisons with two close relatives of wide output converters show that the proposed RS-WOCP con- verter is advantageous for wide output range constant peak power applications.
    IEEE Transactions on Power Electronics 01/2011; 26(10):2925-2935. · 4.08 Impact Factor
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    ABSTRACT: Variable linear or nonlinear loads are necessary for testing medium voltage (MV) high power AC power supplies. Generally, those AC power supplies require performance validation, burn-in, and/or life-time testing under different load conditions, defined by the end-user or standards for the given applications. For this purpose, this paper presents a multilevel converter-based AC regenerative electronic load with One-Cycle Control (OCC), which is based on a five-level diode-clamped multilevel converter and can emulate any impedance load, whether linear or nonlinear, steady or dynamic. Simulation and experimental results are presented to verify the performance of the proposed multilevel AC regenerative load. I. INTRODUCTION
    01/2011;
  • Pengju Sun, Luowei Zhou, K. Smedley
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    ABSTRACT: The paper presents a new wide output range reconfigurable structure (WOR-RS) dc-dc converter, which is an extension of the full bridge isolated dc-dc converter with two output channels by adding an active switch and two diodes. The proposed WOR-RS is able to smoothly reconfigure the two output channels in parallel or series to realize wide output range. With this approach, the output voltage is shared equally in the series operating mode and so is the output current in the parallel operating mode. Therefore, the power rating of devices is significantly reduced compared to traditional isolated full bridge converter and the output rectifiers and filters can distribute power losses and thermal stresses. Operating principle, control strategy, modeling, and stability analysis are illustrated in the paper. An experimental prototype of a 200W DSP-based WOR-RS full-bridge dc-dc converter was built. The experimental results show the steady-state performance and fast dynamic response in the whole output voltage range, and verify the validity and applicability of this converter.
    IECON 2010 - 36th Annual Conference on IEEE Industrial Electronics Society; 12/2010
  • Jun Wen, Liang Zhou, K. Smedley
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    ABSTRACT: This paper introduced Hexagram converter - a new type of multilevel converter for reactive power compensation and harmonics elimination at Medium-Voltage (MV) grids to improve the power quality. The Hexagram converter is composed of six three-phase two-level Voltage Source Converters (VSCs) interconnected through the inductors, and has the advantages of modular structure with easy construction, even and much reduced voltage stress, and easy control. A four-dimensional control method which is composed of three two-level One-Cycle Controllers (OCC) is proposed for the Hexagram converter system. The reactive power compensation and harmonics elimination function has been verified with both simulation model and experimental prototype.
    Energy Conversion Congress and Exposition (ECCE), 2010 IEEE; 10/2010
  • Liang Zhou, K.M. Smedley
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    ABSTRACT: This paper discusses the fault tolerance ability of the hexagram inverter motor drive. Due to its unique interconnecting nature, the hexagram inverter can tolerate one leg failure without modifying the power circuit topology. In the event of one leg failure, the control circuit can reconfigure the trigger signals to maintain a smooth torque operation at a reduced power level. When a leg fails within the inner interconnecting loop, no special postfault strategy is needed; the hexagram inverter can still work properly. When a leg fails outside of the interconnecting loop, a new postfault control strategy is initiated, which controls the two remaining phase currents to maintain an operation with smooth torque. The simulation and experimental results have shown that the hexagram inverter can maintain its operation with smooth torque after a fault.
    IEEE Transactions on Industrial Electronics 09/2010; · 5.17 Impact Factor
  • A. Abramovitz, Tang Cheng, K. Smedley
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    ABSTRACT: An energy regenerating snubber for a forward converter is presented. The proposed snubber uses a tertiary transformer winding and beneficially exploits transformers' leakage inductances. The proposed snubber is capable of resetting the transformer, as well as eliminating leakage inductance voltage spike across the power switch. The proposed snubber recycles the recovered energy partially to the load and partially back to the source. This paper presents theoretical analysis, simulation and experimental results.
    IEEE Transactions on Power Electronics 04/2010; · 4.08 Impact Factor
  • Liang Zhou, K. Smedley
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    ABSTRACT: In this paper, a fault tolerant control method for hexagram inverter motor drive is proposed. Due to its unique topology, the hexagram inverter is able to tolerate certain degree of switch failure with a proper control method. The proposed method consists of fault detection, fault isolation and post fault control. A simple fault isolation method is to use fuses in the DC links to disable the whole inverter module with switch failure. When a fault is detected in one inverter module, it is isolated by turning on all switches temporarily to blow out the fuse in the DC link, the gate drive signals for this faulty inverter module and its interconnecting legs are then disabled. After one inverter module is disabled, the hexagram inverter works in the post fault two-phase mode. The post fault control algorithm is initiated to control the two remaining output currents in order to maintain a smooth torque operation for the motor drive. Simulations and a small-scale PMSM motor drive experiment verified the proposed fault tolerant control system design.
    Applied Power Electronics Conference and Exposition (APEC), 2010 Twenty-Fifth Annual IEEE; 03/2010
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    ABSTRACT: Variable linear or nonlinear loads are critical for testing AC power supplies and power equipment in various operating conditions. At present, most testing loads are based on bulky resistors, capacitors, and inductors on which the testing energy is consumed to generate excessive heat, and moreover, the impedance value is limited by finite combination of these bulky loads. Some commercial electronic loads are available, which provide flexible impedance control but the energy absorbed by the load is still dissipated as heat. The work presented in this paper is a continuous effort of UCI Power Electronics AC load project. A Regenerative AC Electronic Load (RACEL) is developed with One-Cycle Controller (OCC), which doesn't require any Digital Signal Processor (DSP) and software in the control loop. Using a reconfigurable Field Programmable Analog Array (FPAA), the OCC can be integrated into a single FPAA with easy reconfiguration and simple interface structure. The proposed RACEL can emulate any impedance load, linear or nonlinear as well steady or dynamic with the regeneration of the testing energy. Simulation and experimental results are presented to verify the proposed RACEL performance.
    Applied Power Electronics Conference and Exposition (APEC), 2010 Twenty-Fifth Annual IEEE; 03/2010
  • Jun Wen, Liang Zhou, K. Smedley
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    ABSTRACT: A new Hexagram Active Power Filter (APF) is proposed for harmonics elimination at medium-voltage grids. The new converter is composed of six interconnected three-phase standard two-level voltage source converter modules with advantages including modular structure with easy construction and maintenance, no voltage unbalance problem, reduced voltage stress, symmetrical structure with automatic and equal voltage and current sharing, and easy control with well-developed two-level control techniques, etc. In this paper, One-Cycle Control - an excellent control scheme for two-level converters is extended to realize the control of the Hexagram converter for active power filter function. Both simulation and experiment have been conducted and verified the proposed converter and proposed control scheme.
    Applied Power Electronics Conference and Exposition (APEC), 2010 Twenty-Fifth Annual IEEE; 03/2010
  • Source
    Hao Cheng, K.M. Smedley, A. Abramovitz
    [show abstract] [hide abstract]
    ABSTRACT: This paper presents a new wide-input-wide-output dc-dc converter, which is an integration of buck and boost converters via a tapped inductor. Coherent transition between step-down and step-up modes is achieved by a proper control scheme. This paper presents theoretical concepts and experimental results.
    IEEE Transactions on Power Electronics 03/2010; · 4.08 Impact Factor

Publication Stats

2k Citations
205.94 Total Impact Points

Institutions

  • 1994–2009
    • University of California, Irvine
      • • Department of Mechanical and Aerospace Engineering
      • • Department of Electrical Engineering and Computer Science
      Irvine, California, United States
  • 2008
    • University of California, Davis
      Davis, California, United States
  • 2007
    • Shamoon College of Engineering
      Ukreir, Southern District, Israel
  • 1992
    • California Institute of Technology
      Pasadena, California, United States