• Journal of Electrical Engineering and Technology
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• v.6 no.5
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• pp.658-665
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• 2011

In the present paper, a novel fast peak detector for single- or three-phase unsymmetrical voltage sags is proposed. The proposed detector is modified from a single-phase digital phase-locked loop based on a d-q transformation using an all-pass filter (APF). APF generates a virtual phase with $90^{\circ}$ phase delay. However, this virtual phase cannot reflect a sudden change of the grid voltage in the moment of voltage sag, which causes a peak value to be significantly distorted and to settle down slowly. Specifically, the settling time of the peak value is too long when voltage sag occurs around a zero crossing, such as phase $0^{\circ}$ and $180^{\circ}$. This paper describes the operating principle of the APF problem and proposes a modified all-pass filter (MAPF) to mitigate the inherent APF problem. In addition, a new fast peak detector using MAPF is proposed. The proposed detector is able to calculate a peak value within 0.5 ms, even when voltage sag occurs around zero crossing. The proposed fast peak detector is compared with the conventional detector using APF. Results show that the proposed detector has faster detection time in the whole phase range. Furthermore, the proposed fast peak detector can be effectively applied to unsymmetrical three-phase voltage sags. Simulation and experimental results verify the advantages of the proposed detector and MAPF.

• Journal of Advanced Marine Engineering and Technology
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• v.23 no.2
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• pp.210-215
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• 1999

The proposed detector is consists of three-phase sinusoidal signal generator and peak detector. This peak detector can detect the peak voltage value at the state of variable frequency. In experi-ment three-phase sinusoidal signals are generated from D/A converter using IBM PC and deliv-ered to the peak detector. Each signals are squared by multiplier and summed up Peak value is the square root of summed value extracted by square root circuit.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.4
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• pp.586-593
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• 2010

In this paper, I have proposed that the 1st and 2nd AC-DC transformation methods using multi-level pulsating currents and selection switches. Through making the rectified voltage of the proposed AC-DC translation which is similar to reference voltage by selecting from multi-level pulsating currents, the proposed translation has dramatically reduced the ripple voltage. I have compared the performance of the DC voltage, the ripple voltage and the peak to peak voltage of the proposed method with the conventional method. The simulation results show that the proposed 2nd method has the better performance than the 1st method in the point of average DC voltage drop and peak to peak voltage increase.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.50 no.7
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• pp.329-333
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• 2001

The pulsed poser system has been widely used to many applications, such as E/P(Electrostatic Precipitator), DeNox/DeSOx power system, ozon generator, etc. A pulse energy efficiency for load depends on the rising time, peak value, pulse duration and impedance matching, etc. The pulse generator generally required for short pusle duration and high peak value was forced to consider its volume and economy. In this study, developing a compact pulse generator that applied for cascading method to be made of two pulse transformers, we compared cascading voltage with non cascading one by applying the pulse energy to load. Adopting cascading technique to pulse transformer, we found that average cascading voltage was about 60[%] of theoretical value. Maximum cascading ratio was calculated at 60 times compared with non cascading voltage.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.999-1002
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• 1997

In this study, in order to set ELID conditions in the internal grinding wheel, the characteristics with the variations of grit size, output voltage and peak current were examined by using conventional machining center(M/C) equipped with electrolytic in-process dressing(EL1D). The initial working voltage was lowered and the working current was high with increasing grit size. The insulating layer thickness increased, as the final voltage increased with the output voltage and peak current. The initial wear rate of the wheel machined with ELID were measured indirectly by using surface roughness tracer. The initial wear rate of the wheel with ELID increased along with high grit size. In case that the grit size with ELID was low, the output voltage and peak current had to be increased to increase the insulating layer thickness. In case of the high grit size, the output voltage and the peak current were established low, which made the insulating layer thickness decreased.

• Journal of Power Electronics
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• v.19 no.6
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• pp.1351-1365
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• 2019

This paper proposes two modified Z-source inverter topologies, namely an embedded L-Z-source inverter (EL-ZSI) and a coupled inductor L-Z source inverter (CL-ZSI). The proposed topologies offer a high voltage gain with a reduced passive component count and reduction in source current ripple when compared to conventional ZSI topologies. Additionally, they prevent overshoot in the dc-link voltage by suppressing heavy inrush currents. This feature reduces the transition time to reach the peak value of the dc-link voltage, and reduces the risk of component failure and overrating due to the inrush current. EL-ZSI and CL-ZSI possess all of the inherent advantages of the conventional L-ZSI topology while eliminating its drawbacks. To verify the effectiveness of the proposed topologies, MATLAB/Simulink models and scaled down laboratory prototypes were constructed. Experiments were performed at a low shoot through duty ratio of 0.1 and a modulation index as high as 0.9 to obtain a peak dc-link voltage of 53 V. This paper demonstrates the superiority of the proposed topologies over conventional ZSI topologies through a detailed comparative analysis. Moreover, experimental results verify that the proposed topologies would be advantageous for renewable energy source applications since they provide voltage gain enhancement, inrush current, dc-link voltage overshoot suppression and a reduction of the peak to peak source current ripple.

• Journal of the Korea Institute of Military Science and Technology
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• v.23 no.5
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• pp.516-522
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• 2020

In this paper, the frequency detector which detects the clock frequency of the embedded system is proposed and analyzed. The proposed frequency detector is consisted of filter and peak voltage detector. The clock signal is converted from square wave to triangular wave by the filter. The peak voltage of the triangular wave is determined according to the frequency response of filter. The peak voltage detector detects and holds the peak voltage of the signal. Moreover, the proposed clock frequency detector can detect the frequency within 1ms and it gives guarantee of real-time operation.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.245-247
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• 2001

This paper presents a series of simulation results of transient stability on SCOPF operated power system whose transmission capabilities are limited by voltage stability. Three steps of voltage security guidelines, 5[%], 7[%], 10[%] are introduced to increase power transfer from generation centers to load center and observed the effects of voltage guidelines to transient stability for three kinds of load level(peak, medium, off-peak). As a result, dynamic characteristics weren't affected by the voltage security limits in model system, but became worse for the off-peak level than peak case, and sustain oscillations are observed for the all load level. This gives us some intitutions for the development and applications of security limits to use SCOPF program in open electric market.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.7
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• pp.1195-1199
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• 2008

In this paper, peak detector of generator's output voltage and variable gain controller are introduced for a fast dynamic response. The conventional r,m.s, signal detected has inherent time delay, and the dynamic response of generator using conventional PID controller has some problem in sudden load change. In this paper, the peak detector and signal selector with variable gain controller is used to overcome this problem. The main controller can check the voltage state from the peak detector. When a sudden load change, the over-voltage and under-voltage signal from peak detector change the controller's gain and exciter's current reference. The proposed scheme can improve the dynamic response, which is verified from experimental test of 200kW diesel engine-generator.

• The Korean Journal of Physiology and Pharmacology
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• v.21 no.2
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• pp.215-223
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• 2017

The effects of acidic pH on several voltage-dependent ion channels, such as voltage-dependent $K^+$ and $Ca^{2+}$ channels, and hyperpolarization-gated and cyclic nucleotide-activated cation (HCN) channels, were examined using a whole-cell patch clamp technique on mechanically isolated rat mesencephalic trigeminal nucleus neurons. The application of a pH 6.5 solution had no effect on the peak amplitude of voltage-dependent $K^+$currents. A pH 6.0 solution slightly, but significantly inhibited the peak amplitude of voltage-dependent $K^+$ currents. The pH 6.0 also shifted both the current-voltage and conductance-voltage relationships to the depolarization range. The application of a pH 6.5 solution scarcely affected the peak amplitude of membrane currents mediated by HCN channels, which were profoundly inhibited by the general HCN channel blocker $Cs^+$ (1 mM). However, the pH 6.0 solution slightly, but significantly inhibited the peak amplitude of HCN-mediated currents. Although the pH 6.0 solution showed complex modulation of the current-voltage and conductance-voltage relationships, the midpoint voltages for the activation of HCN channels were not changed by acidic pH. On the other hand, voltage-dependent $Ca^{2+}$ channels were significantly inhibited by an acidic pH. The application of an acidic pH solution significantly shifted the current-voltage and conductance-voltage relationships to the depolarization range. The modulation of several voltage-dependent ion channels by an acidic pH might affect the excitability of mesencephalic trigeminal nucleus neurons, and thus physiological functions mediated by the mesencephalic trigeminal nucleus could be affected in acidic pH conditions.