The Experts below are selected from a list of 2148 Experts worldwide ranked by ideXlab platform
Feiyue Wang - One of the best experts on this subject based on the ideXlab platform.
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the exact and unique solution for phase lead and phase Lag Compensation
IEEE Transactions on Education, 2003Co-Authors: Feiyue WangAbstract:Phase-lead and -Lag Compensation is one of the most commonly used techniques for designing control systems in the frequency domain, especially when the Bode diagram or root locus is used. In most cases, the graphic-based approximation or trial-and-error approach has been utilized in the design process. This paper presents the exact and unique solution to the design of phase-lead and phase-Lag Compensation when the desired gains in the magnitude and phase are known at a given frequency. It also gives the concise condition for determining the existence of single-stage lead or Lag Compensation.
Xuehua Wang - One of the best experts on this subject based on the ideXlab platform.
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optimized controller design for lcl type grid connected inverter to achieve high robustness against grid impedance variation
IEEE Transactions on Industrial Electronics, 2015Co-Authors: Xinbo Ruan, Weiwei Li, Xuehua WangAbstract:Capacitor-current-feedback active damping is an effective method to suppress the $LCL$ -filter resonance in grid-connected inverters. However, due to the variation of grid impedance, the $LCL$ -filter resonance frequency will vary in a wide range, which challenges the design of the capacitor-current-feedback coefficient. Moreover, if the resonance frequency is equal to one-sixth of the sampling frequency $(f_{s}/6)$ , the digitally controlled $LCL$ -type grid-connected inverter can be hardly stable no matter how much the capacitor-current-feedback coefficient is. In this paper, the optimal design of the capacitor-current-feedback coefficient is presented to deal with the wide-range variation of grid impedance. First, the gain margin requirements for system stability are derived under various resonance frequencies. By evaluating the effect of grid impedance on gain margins, an optimal capacitor-current-feedback coefficient is obtained. With this feedback coefficient, stable operations will be retained for all resonance frequencies except $f_{s} /6$ . Second, in order to improve system stability for a resonance frequency of $f_{s} /6$ , a phase-Lag Compensation for the loop gain is proposed. Finally, a 6-kW prototype is tested to verify the proposed design procedure.
Rosalind J Sadleir - One of the best experts on this subject based on the ideXlab platform.
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biocompatible high precision wideband improved howland current source with lead Lag Compensation
IEEE Transactions on Biomedical Circuits and Systems, 2013Co-Authors: Aaron S Tucker, R M Fox, Rosalind J SadleirAbstract:The Howland current pump is a popular bioelectrical circuit, useful for delivering precise electrical currents. In applications requiring high precision delivery of alternating current to biological loads, the output impedance of the Howland is a critical figure of merit that limits the precision of the delivered current when the load changes. We explain the minimum operational amplifier requirements to meet a target precision over a wide bandwidth. We also discuss effective Compensation strategies for achieving stability without sacrificing high frequency output impedance. A current source suitable for Electrical Impedance Tomography (EIT) was simulated using a SPICE model, and built to verify stable operation. This current source design had stable output impedance of 3.3 MΩ up to 200 kHz, which provides 80 dB precision for our EIT application. We conclude by noting the difficulty in measuring the output impedance, and advise verifying the plausibility of measurements against theoretical limitations.
Xinbo Ruan - One of the best experts on this subject based on the ideXlab platform.
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optimized controller design for lcl type grid connected inverter to achieve high robustness against grid impedance variation
IEEE Transactions on Industrial Electronics, 2015Co-Authors: Xinbo Ruan, Weiwei Li, Xuehua WangAbstract:Capacitor-current-feedback active damping is an effective method to suppress the $LCL$ -filter resonance in grid-connected inverters. However, due to the variation of grid impedance, the $LCL$ -filter resonance frequency will vary in a wide range, which challenges the design of the capacitor-current-feedback coefficient. Moreover, if the resonance frequency is equal to one-sixth of the sampling frequency $(f_{s}/6)$ , the digitally controlled $LCL$ -type grid-connected inverter can be hardly stable no matter how much the capacitor-current-feedback coefficient is. In this paper, the optimal design of the capacitor-current-feedback coefficient is presented to deal with the wide-range variation of grid impedance. First, the gain margin requirements for system stability are derived under various resonance frequencies. By evaluating the effect of grid impedance on gain margins, an optimal capacitor-current-feedback coefficient is obtained. With this feedback coefficient, stable operations will be retained for all resonance frequencies except $f_{s} /6$ . Second, in order to improve system stability for a resonance frequency of $f_{s} /6$ , a phase-Lag Compensation for the loop gain is proposed. Finally, a 6-kW prototype is tested to verify the proposed design procedure.
Aaron S Tucker - One of the best experts on this subject based on the ideXlab platform.
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biocompatible high precision wideband improved howland current source with lead Lag Compensation
IEEE Transactions on Biomedical Circuits and Systems, 2013Co-Authors: Aaron S Tucker, R M Fox, Rosalind J SadleirAbstract:The Howland current pump is a popular bioelectrical circuit, useful for delivering precise electrical currents. In applications requiring high precision delivery of alternating current to biological loads, the output impedance of the Howland is a critical figure of merit that limits the precision of the delivered current when the load changes. We explain the minimum operational amplifier requirements to meet a target precision over a wide bandwidth. We also discuss effective Compensation strategies for achieving stability without sacrificing high frequency output impedance. A current source suitable for Electrical Impedance Tomography (EIT) was simulated using a SPICE model, and built to verify stable operation. This current source design had stable output impedance of 3.3 MΩ up to 200 kHz, which provides 80 dB precision for our EIT application. We conclude by noting the difficulty in measuring the output impedance, and advise verifying the plausibility of measurements against theoretical limitations.
