K.M. Smedley

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

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Publications (190)367.23 Total impact

  • Source
    A. Khoshkbar Sadigh · K.M. Smedley
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    ABSTRACT: Voltage sag detection method has a significant impact on the performance of dynamic voltage restorer (DVR). This paper proposes a fundamental voltage amplitude detection method which is applicable in both single/three-phase systems for DVR applications. Advantages of the proposed method include application in distorted power grid without any low-pass filter, precise and reliable detection, simple computation and implementation without using a phased locked loop and lookup table. The proposed method has been simulated and implemented experimentally and tested under various conditions considering all possible cases such as different amounts of voltage sag depth (VSD), different amounts of point-on-wave (POW) at which voltage sag occurs, harmonic distortion, line frequency variation, and phase jump (PJ). A detailed procedure to design the threshold band for comparator is presented. According to the achieved results and detailed analysis, maximum ripple of the calculated fundamental voltage amplitude is ±0.3% in normal condition of line frequency and ±1% in the case of ±1 Hz variation of 60 Hz line frequency. In addition, the error between the actual fundamental voltage amplitude and the calculated one is almost zero in normal condition of line frequency and maximum of ±0.25% in the case of line frequency variation with excessive-harmonic distortion. Furthermore, detection time (DT) of the proposed method is analyzed in detail for different amounts of VSD, POW and PJ. The best and worst detection time of the proposed method were measured 1 and 8.8 ms, respectively. Finally, the proposed method has been compared with other methods available in the literature.
    Full-text · Article · Jan 2016 · Electric Power Systems Research
  • Jia Yao · Alexander Abramovitz · Keyue Ma Smedley
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    ABSTRACT: This paper introduces a SEPIC-derived bidirectional dc–dc converter. The proposed converter utilizes tapped inductor and charge pump techniques to achieve steep voltage conversion ratio and an active lossless regenerative snubber to attain lossless switching and high efficiency. The paper presents the principle of operation, steady-state analyses, and experimental results obtained from a 400-W, 48-V/380-V prototype. The efficiency of the proposed topology is demonstrated to peak at 96.4% for boost mode and 95.0% for buck mode.
    No preview · Article · Dec 2015 · IEEE Transactions on Power Electronics
  • Ben Zhao · Alexander Abramovitz · Keyue Smedley
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    ABSTRACT: Family of single-phase single-stage bridgeless power factor correctors based on tapped-inductor buck-boost converters is introduced. The converters’ family has the merits of reduced component count and alleviated losses in the conduction path. The feasibility of the proposed topologies was verified by simulation and experimental results.
    No preview · Article · Dec 2015 · IEEE Transactions on Power Electronics
  • Jia Yao · Alexander Abramovitz · Keyue Ma Smedley
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    ABSTRACT: This paper introduces a SEPIC-derived converter suited for alternative energy generation applications. The proposed converter utilizes tapped inductor and charge pump techniques to achieve high step-up gain and a passive regenerative snubber to attain high efficiency. Compared with earlier counterparts, the proposed converter has the advantage of continuous input current, which can be helpful in attaining accurate tracking of maximum power point of solar panels. The paper presents principle of operation, theoretical analysis, and design guidelines. Theoretical expectations were confirmed by simulation and experimental results.
    No preview · Article · Oct 2015 · IEEE Transactions on Power Electronics
  • Source
    Bin Wu · Shouxiang Li · Keyue Ma Smedley · Sigmond Singer
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    ABSTRACT: A family of “Two-Switch Boosting Switched-Capacitor Converters (TBSC)” is introduced, which distinguishes itself from the prior arts by symmetrically interleaved operation, reduced output ripple, low yet even voltage stress on components, and systematic expandability. Along with the topologies, a modeling method is formulated, which provokes the converter regulation method through duty cycle and frequency adjustment. In addition, the paper also provides guidance for circuit components and parameter selection. A 1-kW 3X TBSC was built to demonstrate the converter feasibility, regulation capability via duty cycle and frequency, which achieved a peak efficiency of 97.5% at the rated power.
    Full-text · Article · Oct 2015 · IEEE Transactions on Power Electronics
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    Yuval Beck · Nir Eden · Shira Sandbank · Sigmund Singer · Keyue Ma Smedley
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    ABSTRACT: In this paper the power losses of efficient capacitive converters with multitude transfer ratio values are discussed. The loss mechanism circuits, based on general transposed series parallel (GTSP) topology, is studied and the losses are calculated, which in turn enables the 'bottlenecks' to be identified and overcome. The calculations show that for a given number of switching cells the power losses of such converters are mainly dependent on the voltage conversion ratio, the topology function, the resistances of the switches in on and off states, the ESR of the capacitors, the switching frequency, the voltage drop, and the load. The theory explains the fact that was observed in experiments, that for low voltage conversion ratio values, efficiency decrease was measured. It is shown that for these low voltage ratio values the mechanism associated to the off resistance of the switches is more dominant and reduces the efficiency. This power loss estimation can be used as a powerful tool for the performance optimization of capacitive converters. The theoretical results are verified experimentally on a 10-cell GTSP converter prototype. The experimental results show good agreement with the proposed theory.
    Full-text · Article · Sep 2015 · Circuits and Systems I: Regular Papers, IEEE Transactions on
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    A. Khoshkbar-Sadigh · K.M. Smedley
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    ABSTRACT: The current deregulation trend in the electric power generation has led the utilities to adapt solar energy generation into their existing infrastructure. The main challenge of solar energy integration into power grid is its time-varying (intermittency) nature due to cloud shading of PV panels which depends on weather conditions. This paper discusses the impacts of large-scale solar energy penetration into power distribution network. Moreover, the necessity of time-series simulation and field measurement data to investigate the impacts of intermittency of large-scale solar energy penetration is explained. It has been shown that the sampling rate of measurement data has an important role while inadequate sampling rate of measurement data may lead to miss the high-variability points which have significant effects on the operation of system. In this paper, the real field measurement data of a sample circuit form Southern California (SCE) are considered.
    Full-text · Article · Jun 2015
  • B. Wu · K. Smedley
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    ABSTRACT: A new Isolated Hybrid Boosting Converter (IHBC) is proposed in this paper. It employs fly-back structure at primary side of transformer and a Bipolar Voltage Multiplier (BVM) structure at secondary side to increase the voltage gain. The circuit alternates between forward and fly-back modes, which avoids the use of magnetic reset winding. The proposed converter has symmetrical configuration with interleaving capability at secondary side. Due to the cascading flying capacitors, the high voltage rating output filter capacitor which exists in most of other converters can be eliminated. In addition, an energy regenerative snubber is utilized to recycle the leakage energy at primary side. A 200W prototype that converts 35V to 400V was built and efficiency of 91.2% was achieved at rated power. The simulation and experimental results both verified the feasibility of proposed converter.
    No preview · Article · May 2015
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    R. Naderi · K. Smedley
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    ABSTRACT: This paper proposes a new five-level hybrid topology combining features of neutral point clamped and flying capacitor inverters. The proposed topology provides a tradeoff between different component counts to achieve a good loss distribution, avoid direct series connection of semiconductor devices, keep the balanced operation of dc-link capacitors while keeping the number of costly components such as capacitors and switches low. The required modulation strategy is developed and the operation of the proposed topology is studied. The features of the proposed topology are investigated and compared to other available topologies. Simulation results are provided to verify the performance of the converter for medium voltage applications.
    Full-text · Article · May 2015
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    ABSTRACT: Diversity of software packages to simulate the power system circuits is considerable. It is challenging to transfer power system circuit model data (PSCMD) among different software tools and rebuild the same circuit in the second software environment. This paper proposes a unified platform (UP) where PSCMD are stored in a spreadsheet file with a defined format. Script-based PSCMD transfer applications, written in MATLAB, have been developed for a set of software to read the circuit model data from the UP spreadsheet and reconstruct the circuit in the destination software. This significantly eases the process of transferring circuit model data between each pair of software tools. In this paper ETAP, OpenDSS, Grid LabD, and DEW are considered. In order to test the developed PSCMD transfer applications, circuit model data of a test circuit and an actual sample circuit from a Californian utility company, both built in CYME, were exported into the spreadsheet file according to the UP format. Thereafter, circuit model data were imported successfully from the spreadsheet files into all above mentioned software using the PSCMD transfer applications developed for each software individually. Finally, load flow analysis is performed in all software and the obtained results match with each other.
    Full-text · Article · Mar 2015
  • Source
    Alexander Abramovitz · Ben Zhao · Keyue Smedley

    Full-text · Article · Jan 2015 · IEEE Transactions on Power Electronics
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    Alexander Abramovitz · Jia Yao · Keyue Smedley
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    ABSTRACT: This paper revisits the switched flow graph (SFG) technique. A general and unified equivalent SFG model of a three-terminal switcher encountered in regular and tapped inductor converters operating in the continuous conduction mode is proposed. The model can be applied to most PWM topologies and facilitates construction of a complete flow graph of a given converter. The approach can be helpful in theoretical analysis and derivation of analytical expressions of converter's small-signal transfer functions. The suggested methodology extends the previously proposed SFG analysis technique and alleviates the principal difficulties involved. Furthermore, the approach is straightforward and expeditious. Application guidelines and examples are presented and compared to simulation and earlier theoretical results.
    Full-text · Article · Jan 2015 · IEEE Transactions on Power Electronics
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    V. Yaskiv · A. Abramovitz · K. Smedley · A. Yaskiv
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    ABSTRACT: This paper evaluates the performance of magnetic amplifier regulator in isolated off-line power supplies with power factor correction stage. A research of operation modes of power converter, based on high frequency magnetic amplifiers, with power factor correction was conducted for the first time. Simplified controller circuitry is suggested and analyzed. Experimental results are reported.
    Full-text · Article · Jan 2015
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    Bin Wu · Shouxiang Li · Sigmund Singer · Keyue Ma Smedley
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    ABSTRACT: Switched-capacitor (SC) converters were initially introduced for low-power applications and monolithic integration. In recent years, SC converter has found high-power applications. However, voltage regulation remains an issue. This paper addresses regulation challenges for high-power SC converters, based on charge-balance transient-calculation (CT) modeling method and peak current stress estimation. With the help of CT model, due to its accuracy and comprehensive relationship, circuit and control parameters' impacts on regulation become straightforward and concerns on components stresses can be addressed quantitatively. The suitability of CT method for regulation analysis is confirmed by comparison with traditional modeling methods. The CT method is used in a 1-kW 3X two-switch boosting switched-capacitor converter (TBSC) circuit for steady-state analysis and current stress estimation. The soft rising input current and nature interleaving properties of 3X TBSC make it well suited for high-power application. Finally, the small-signal model of the 3X TBSC is developed and a closed-loop operation is achieved under 1 kW power rating.
    Full-text · Article · Jan 2015 · IEEE Transactions on Power Electronics
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    Bin Wu · Shouxiang Li · Yao Liu · Keyue Ma Smedley
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    ABSTRACT: A hybrid boosting converter (HBC) with collective advantages of regulation capability from its boost structure and gain enhancement from its voltage multiplier structure is proposed in this paper. The new converter incorporates a bipolar voltage multiplier, featuring symmetrical configuration, single inductor and single switch, high gain capability with wide regulation range, low component stress, small output ripple and flexible extension, which make it suitable for front-end PV system and some other renewable energy applications. The operation principal, component stress, and voltage ripple are analyzed in this paper. Performance comparison and evaluation with a number of previous single-switch single-inductor converters are provided. A 200-W 35 to 380 V second-order HBC prototype was built with peak efficiency at 95.44%. The experimental results confirms the feasibility of the proposed converter.
    Full-text · Article · Jan 2015 · IEEE Transactions on Power Electronics
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    Full-text · Article · Jan 2015 · IEEE Transactions on Power Electronics
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    S. Singer · Y. Beck · W. Bin · K. Smedley
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    ABSTRACT: In this paper the connectivity of capacitive converters in general and General Transposed Series-Parallel converter in particular to photovoltaic sources is discussed. The paper describes the compatibility of capacitive converters to photovoltaic as soft sources since the voltage source can adjust itself to the change in the capacitors voltage and therefore reduces the inherent pulsating currents of switched capacitors converters when they are connected to rigid sources. The theory is demonstrated by simulation and the simulation results are in full agreement with the presented theory. The results show that if not better at least capacitive converters can be adequate interface with soft sources and their ability to be integrated makes this technology attractive.
    Full-text · Conference Paper · Dec 2014
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    Ben Zhao · Alexander Abramovitz · Keyue Smedley
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    ABSTRACT: This paper introduces a high gain Single-Stage Boosting Inverter (SSBI). The proposed topology can be used for alternative energy generation and particularly in photovoltaic applications. As compared to the traditional two stage approach, SSBI has a simple topology, low decoupling capacitor and low component count. SSBI employs One Cycle Controller to generate its AC output and attain DC-AC power decoupling. The paper presents theoretical analysis, simulation and experimental results obtained from a 200W prototype. The experimental results reveal that the proposed single stage inverter can achieve high voltage boost, good quality of AC output waveform, and good conversion efficiency.
    Full-text · Article · Nov 2014
  • S. Li · B. Wu · K. Smedley · S. Singer
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    ABSTRACT: Switched-Capacitor (SC) technologies have been an active research topic for DC-DC power conversion for many years. Without participation of inductor, they have the potential to achieve small size, light weight and high-power density. From literature research, most of the SC converters reported were implemented in low power level in the range of 5 to 50 watts. Typically they have discontinuous input current and use a large number of active switches. Recently, a new two-switch boost switched-capacitor (TBSC) converter was reported in [1] that achieves automatic interleaved DC-DC conversion with only two active switches. The TBSC converter can step up the input voltage by N times, where N=2,3,4,⋯, with continuous input current and small output voltage ripple. This paper explores the feasibility of engaging this TBSC converter for high power applications in the kilowatts level with 3X gain. A simplified modeling method and analysis method is presented to provide solid guidance for analysis and design of the TBSC converter. A 1-kW 150/450-V prototype was implemented that achieved a peak efficiency of 97.5% at full load.
    No preview · Article · Nov 2014
  • Source
    Chaitanya Vartak · Alexander Abramovitz · Keyue Ma Smedley
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    ABSTRACT: An energy regenerative passive snubber for transformer isolated converters is proposed. The snubber is implemented on the transformer's primary and secondary windings. The proposed snubber significantly reduces the voltage spike across the switch caused by the transformer's primary inductance upon switch turn-off and facilitates the fast ramping up of the transformer secondary current. In addition, the proposed snubber provides lossless zero voltage turn off and zero current turn on conditions for the power switch. Experimental example of a flyback converter has shown measured efficiency exceeding 90%. This paper describes the principle of operation and presents approximate theoretical analysis and design guidelines of the proposed snubber. Simulation and experimental results are also reported. The proposed energy regenerating snubber is best suited for flyback and SEPIC converters and can also be adapted to other transformer isolated topologies.
    Full-text · Article · Nov 2014 · IEEE Transactions on Power Electronics

Publication Stats

4k Citations
367.23 Total Impact Points

Institutions

  • 1994-2016
    • University of California, Irvine
      • Department of Electrical Engineering and Computer Science
      Irvine, California, United States
  • 2008
    • University of California, Davis
      • Department of Electrical and Computer Engineering
      Davis, California, United States
  • 2004
    • Zhejiang University
      Hang-hsien, Zhejiang Sheng, China
  • 1992
    • California Institute of Technology
      Pasadena, California, United States