The Experts below are selected from a list of 56406 Experts worldwide ranked by ideXlab platform

Dong-wook Seo - One of the best experts on this subject based on the ideXlab platform.

  • Capacitance Tuning Method for Maximum Output Power in Multiple-Transmitter Wireless Power Transfer System
    IEEE Access, 2020
    Co-Authors: Seon-jae Jeon, Dong-wook Seo
    Abstract:

    It is common knowledge that wireless Power transfer (WPT) systems with multiple transmitters (Txs) and a single receiver (Rx) have robust efficiency against lateral misalignment. However, the unnecessary coupling among Txs in actual multi-Tx WPT systems causes transmission efficiency degradation, and then additional tuning work is required to adjust some system parameters, such as the phase or frequency of Tx sources. Moreover, the frequency-splitting phenomenon caused by over-coupling between the Txs and Rx still occurs in multi-Tx systems. Thus, Output Power degradation is inevitable in the over-coupled state. In this article, we propose an optimal capacitance tuning method that is applicable to multi-Tx WPT systems. A multi-Tx WPT system tuned with the optimal capacitances, which are obtained from the critical coupling condition between Txs and Rx, not only compensates the inner coupling among Txs but also achieves the Maximum Output Power in the over-coupled state. To verify the validity of the proposed method, we implemented two-and three-Tx and single Rx WPT systems and measured the Output Power of load with respect to the Rx position along the $x$ - and $y$ -axes. As a result, with the proposed method without any changes in the operating frequency or phase, the systems could deliver higher Output Power than the conventional phase-controlled system. In particular, with the proposed method, the systems maintained the constant Maximum transmission efficiency of 80% in the over-coupled state.

  • Maximum Output Power Improvement Using Negative Coil in Over-Coupled WPT System
    IEEE Microwave and Wireless Components Letters, 2020
    Co-Authors: Seon-jae Jeon, Dong-wook Seo
    Abstract:

    Conventional two-coil wireless Power transfer (WPT) systems achieve the Maximum Output Power at the optimal distance. In the over-coupled state, in which the distance between coils is shorter than the optimal distance, the input impedance is significantly higher than that with the optimal distance. As a result, the Output Power at the load is dramatically decreased. In this letter, we propose a method to improve the Maximum Output Power by applying a negative-impedance converter (NIC) to an additional coil. The proposed system can drastically improve the Output Power at a load even in the over-coupled state because the negative coil eliminates the impedance reflected by mutual coupling between coils. To validate the proposed method, the NIC was implemented with an operational amplifier and four identical coils. In the experiment, the proposed system transferred enhanced Power, which was three times higher than the Maximum Output Power of the conventional system.

  • Optimal Coupling to Achieve Maximum Output Power in a WPT System
    IEEE Transactions on Power Electronics, 2016
    Co-Authors: Dong-wook Seo, Jae-ho Lee, Hyung-soo Lee
    Abstract:

    In the wireless Power transfer systems, a coupling coefficient is one of the measures of performance. In particular, the coupling coefficient at critical coupling does not ensure Maximum system energy efficiency but guarantee Maximum Output Power to the load. As the coupling coefficient goes beyond the critical-coupled state, Output Power begins to decline. In this letter, we propose a method to maximize Output Power even in an overcoupled state as in the critical-coupled state by adjusting the capacitance of the resonator. Our proposal is verified by comparing the calculations and simulations with measurements, and they are in good agreement.

Anthony J Springthorpe - One of the best experts on this subject based on the ideXlab platform.

  • what limits the Maximum Output Power of long wavelength algainas inp laser diodes
    IEEE Journal of Quantum Electronics, 2002
    Co-Authors: Joachim Piprek, J K White, Anthony J Springthorpe
    Abstract:

    We analyze the high-temperature continuous-wave performance of 1.3-/spl mu/m AlGaInAs/InP laser diodes grown by digital alloy molecular-beam epitaxy. Commercial laser software is utilized that self-consistently combines quantum-well bandstructure and gain calculations with two-dimensional simulations of carrier transport, wave guiding, and heat flow. Excellent agreement between simulation and measurements is obtained by careful adjustment of material parameters in the model. Joule heating is shown to be the main heat source; quantum-well recombination heat is almost compensated for by Thomson cooling. Auger recombination is the main carrier loss mechanism at lower injection current. Vertical electron escape into the p-doped InP cladding dominates at higher current and causes the thermal Power roll-off. Self-heating and optical gain reduction are the triggering mechanisms behind the leakage escalation. Laser design variation is shown to allow for a significant increase in the Maximum Output Power at high temperatures.

  • What limits the Maximum Output Power of long-wavelength AlGaInAs/InP laser diodes?
    IEEE Journal of Quantum Electronics, 2002
    Co-Authors: Joachim Piprek, J K White, Anthony J Springthorpe
    Abstract:

    We analyze the high-temperature continuous-wave performance of 1.3-/spl mu/m AlGaInAs/InP laser diodes grown by digital alloy molecular-beam epitaxy. Commercial laser software is utilized that self-consistently combines quantum-well bandstructure and gain calculations with two-dimensional simulations of carrier transport, wave guiding, and heat flow. Excellent agreement between simulation and measurements is obtained by careful adjustment of material parameters in the model. Joule heating is shown to be the main heat source; quantum-well recombination heat is almost compensated for by Thomson cooling. Auger recombination is the main carrier loss mechanism at lower injection current. Vertical electron escape into the p-doped InP cladding dominates at higher current and causes the thermal Power roll-off. Self-heating and optical gain reduction are the triggering mechanisms behind the leakage escalation. Laser design variation is shown to allow for a significant increase in the Maximum Output Power at high temperatures.

Seungho Song - One of the best experts on this subject based on the ideXlab platform.

Joachim Piprek - One of the best experts on this subject based on the ideXlab platform.

  • what limits the Maximum Output Power of long wavelength algainas inp laser diodes
    IEEE Journal of Quantum Electronics, 2002
    Co-Authors: Joachim Piprek, J K White, Anthony J Springthorpe
    Abstract:

    We analyze the high-temperature continuous-wave performance of 1.3-/spl mu/m AlGaInAs/InP laser diodes grown by digital alloy molecular-beam epitaxy. Commercial laser software is utilized that self-consistently combines quantum-well bandstructure and gain calculations with two-dimensional simulations of carrier transport, wave guiding, and heat flow. Excellent agreement between simulation and measurements is obtained by careful adjustment of material parameters in the model. Joule heating is shown to be the main heat source; quantum-well recombination heat is almost compensated for by Thomson cooling. Auger recombination is the main carrier loss mechanism at lower injection current. Vertical electron escape into the p-doped InP cladding dominates at higher current and causes the thermal Power roll-off. Self-heating and optical gain reduction are the triggering mechanisms behind the leakage escalation. Laser design variation is shown to allow for a significant increase in the Maximum Output Power at high temperatures.

  • What limits the Maximum Output Power of long-wavelength AlGaInAs/InP laser diodes?
    IEEE Journal of Quantum Electronics, 2002
    Co-Authors: Joachim Piprek, J K White, Anthony J Springthorpe
    Abstract:

    We analyze the high-temperature continuous-wave performance of 1.3-/spl mu/m AlGaInAs/InP laser diodes grown by digital alloy molecular-beam epitaxy. Commercial laser software is utilized that self-consistently combines quantum-well bandstructure and gain calculations with two-dimensional simulations of carrier transport, wave guiding, and heat flow. Excellent agreement between simulation and measurements is obtained by careful adjustment of material parameters in the model. Joule heating is shown to be the main heat source; quantum-well recombination heat is almost compensated for by Thomson cooling. Auger recombination is the main carrier loss mechanism at lower injection current. Vertical electron escape into the p-doped InP cladding dominates at higher current and causes the thermal Power roll-off. Self-heating and optical gain reduction are the triggering mechanisms behind the leakage escalation. Laser design variation is shown to allow for a significant increase in the Maximum Output Power at high temperatures.

Julki Seok - One of the best experts on this subject based on the ideXlab platform.

  • Maximum Output Power control of wind generation system considering loss minimization of machines
    Conference of the Industrial Electronics Society, 2004
    Co-Authors: Ahmed G Abokhalil, Julki Seok
    Abstract:

    This paper proposes a Maximum Output control of wind Power generation system considering loss minimization of machines. The wind turbine has its own optimum rotational speed which produce the Maximum Power conversion for the given dimension and wind speed. Even at this optimum speed, the generator cannot produce the Maximum Output Power due to the useless machine loss. In general, the machine loss can be reduced by the decreasing the flux level, resulting in the significant reduction of the core loss. For the vector-controlled induction machine drives, the d-axis current controls the excitation level and the q-axis current controls the generator torque, by which the speed of the induction generator is controlled according to the variation of the wind speed in order to produce the Maximum Output Power. The generator reference speed is adjusted according to the optimum tip-speed ratio. The generated Power flows into the utility grid through the back-to-back PWM converter. The grid-side converter controls the dc link voltage and the line-side Power factor by the q-axis and the d-axis current control, respectively. Experimental results are shown to verify the validity of the proposed scheme.

  • variable speed wind Power generation system based on fuzzy logic control for Maximum Output Power tracking
    Power Electronics Specialists Conference, 2004
    Co-Authors: Ahmed G Abokhalil, Dongchoon Lee, Julki Seok
    Abstract:

    This paper proposes a variable speed control scheme of grid-connected wind Power generation system using cage-type induction generators, which is based on a fuzzy logic control. The induction generator is operated in indirect vector control mode, where the d-axis current controls the excitation level and the q-axis current controls the generator torque, by which the speed of the induction generator is controlled according to the variation of the wind speed in order to produce the Maximum Output Power. The generated Power flows into the utility grid through the back-to-back PWM converter. The grid-side converter controls the DC link voltage and the line-side Power factor by the q-axis and the d-axis current control, respectively. Experimental results are shown to verify the validity of the proposed scheme.

  • variable speed wind Power generation system based on fuzzy logic control for Maximum Output Power tracking
    Power Electronics Specialists Conference, 2004
    Co-Authors: Ahmed G Abokhalil, Dongchoon Lee, Julki Seok
    Abstract:

    This paper proposes a variable speed control scheme of grid-connected wind Power generation system using cage-type induction generators, which is based on a fuzzy logic control. The induction generator is operated in indirect vector control mode, where the d-axis current controls the excitation level and the q-axis current controls the generator torque, by which the speed of the induction generator is controlled according to the variation of the wind speed in order to produce the Maximum Output Power. The generated Power flows into the utility grid through the back-to-back PWM converter. The grid-side converter controls the DC link voltage and the line-side Power factor by the q-axis and the d-axis current control, respectively. Experimental results are shown to verify the validity of the proposed scheme.