• Title/Summary/Keyword: THD

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Current THD Improvement of Valley-Fill Rectifier (밸리-필 정류기의 전류 THD 개선)

  • Lee, Chi-Hwan;Choi, Nam-Yerl
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.22 no.1
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    • pp.87-94
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    • 2008
  • A method for improving current THD of Valley-fill rectifier is proposed in this paper. The proposed topology combines a boosting inductor with Valley-fill rectifier which carry out AC/DC conversion and PFC simultaneously The boosting effect by PWM switching makes low THD current and improve of Valley-fill rectifier. The operation modes and THD of input current are analyzed as applied the boosting inductor, and the optimum value of boosting inductor is determined A 100[W] single-stage converter has been designed and tested. Experimental results are resented to verify the validity of the proposed method.

Improvement of current THD of three-phase grid-connected inverters using repetitive controller (반복제어기를 적용한 3상 계통연계형 인버터의 전류 THD 개선)

  • Lee, Hyungseok;Song, Joongho
    • Proceedings of the KIPE Conference
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    • pp.153-154
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    • 2018
  • 본 논문은 인버터의 출력단과 계통사이에 비선형부하가 연결되어 있는 상황에서 계통 전류의 THD를 개선하기 위해 반복제어기를 적용한다. 반복제어기는 주기적인 오차를 모델링하고 미리 보상하여 정상상태시 오차를 줄이는 목적으로 설계된 제어기이기에 계통전류 THD 개선에 효과적이다. 본 논문은 인버터의 공급전력이 부하의 소비전력보다 큰 경우 또는 부하의 소비전력보다 작은 경우에도 계통의 전류 THD는 개선되도록 하는 알고리즘을 제안한다. 시뮬레이션의 결과를 통해 계통 전류의 THD 개선을 확인한다.

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Control Method for Reducing the THD of Grid Current of Three-Phase Grid-Connected Inverters Under Distorted Grid Voltages

  • Tran, Thanh-Vu;Chun, Tae-Won;Lee, Hong-Hee;Kim, Heung-Geun;Nho, Eui-Cheol
    • Journal of Power Electronics
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    • v.13 no.4
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    • pp.712-718
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    • 2013
  • This paper proposes a control method for reducing the total harmonic distortion (THD) of the grid current of three-phase grid-connected inverter systems when the grid voltage is distorted. The THD of the grid current caused by grid voltage harmonics is derived by considering the phase delay and magnitude attenuation due to the hardware low-pass filter (LPF). The Cauchy-Schwarz inequality theory is used in order to search more easily for the minimum point of the THD. Both the gain and angle of the compensation voltage at the minimum point of the THD of the grid current are derived with the variation of cut-off frequencies of the hardware LPF. Simulation and experimental results show the validity of the proposed control methods.

Antibacterial activity of Tonghyeonipal-dan against Methicillin-resistant Staphylococcus aureus (통현이팔단 에탄올 추출물의 Methicillin Resistant Staphylococcus aureus에 대한 항균활성)

  • KIM, In-Won;KANG, Ok-Hwa;KONG, Ryong;KWON, Dong-Yeul
    • The Korea Journal of Herbology
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    • v.30 no.5
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    • pp.15-21
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    • 2015
  • Objectives : Methicillin-resistantStaphylococcus aureus(MRSA) is a human pathogen. New antibacterial agents are needed to treat MRSA-related infections. This study investigated the antibacterial activity of EtOH 70% extracts ofTonghyeonipal-dan(THD) which prescription is composed of oriental medicine against MRSA.Methods : The antibacterial activity of THD was evaluated against MRSA strains by using the Disc diffusion method, broth microdilution method, Checkerboard dilution test, and Time-kill test; its mechanism of action was investigated by bacteriolysis, detergent or ATPase inhibitors were used.Results : The minimum inhibitory concentration (MIC) of THD is 1,000~2,000 μg/mL against MRSA. In the checkerboard dilution test, fractional inhibitory concentration index (FICI) of THD in combination with antibiotics indicated synergy or partial synergism againstS. aureus. Furthermore, a time-kill assay showed that the growth of the tasted bacteria was considerably inhibited after 24 h of treatment with the combination of THD with selected antibiotics. For measurement of cell membrane permeability, THD 500 μg/mL along with concentration of Triton X-100 (TX) and Tris-(hydroxymethyl) aminomethane (TRIS) were used. In the other hand, N,N-dicyclohexylcarbodimide (DCCD) and Sodium azide (NaN3) were used as an inhibitor of ATPase. TX, TRIS, DCCD and NaN3 cooperation againstS. aureusshowed synergistic action.Conclusions : Accordingly, antimicrobial activity of THD was affected by cell membrane and inhibitor of ATPase were assessed. These results suggest that THD has antibacterial activity, and that THD extract offers great potential as a natural antibiotic against MRSA.

LCL Filter Design for Grid-connected PCS Using Total Harmonic Distortion and Ripple Attenuation Factor (총고조파 왜율과 리플 감쇄율을 이용한 계통연계형 PCS용 LCL 필터 설계)

  • Park, Jong-Hyoung;Chi, Min-Hun;Kim, Heung-Geun;Chun, Tae-Won;Nho, Eui-Cheol
    • The Transactions of the Korean Institute of Power Electronics
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    • v.15 no.3
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    • pp.235-243
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    • 2010
  • This paper describes a design method of LCL filter for grid-connected three-phase PWM inverter. First, by analyzing the ripple component of phase voltages and currents according to the PWM pattern of grid-connected three-phase inverter, the RMS value of the current ripple can be calculated. Then based on the analysis, the current THD in the inverter-side can be defined. After that by analyzing the dependency between the current THD of the system and the current ripple attenuation, the parameter of LCL filter can be designed. Finally, the described LCL filter design method is verified by showing a good agreement between the target current $THD_g$ and the actual one through the simulation and experiment.

The Design of Concentric Winding Type IPMSM For Low Back EMF THD (집중권 매입형 영구자석 전동기의 역기전압 THD 저감설계)

  • Kim, Young-Kyoun;Kim, Sung-Il;Hong, Jung-Pyo
    • Proceedings of the KIEE Conference
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    • pp.1270-1272
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    • 2005
  • This paper presents a method to reduce the back-emf THD(Total Harmonic Distortion) for the Concentric winding type Interior Permanent Magnet Synchronous Motor(CIPMSM). In the CIPMSM, many design variables and their complicated combinations must be considered to reduce the back-emf THD, but it requires a lot of time and efforts. Therefore, this paper suggests the optimized solution with two simple design parameters using MINITAB software.

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THD Analysis ol Bimetal Bearing (바이메탈 베어링의 THD해석)

  • 한동철;조명래;정진영
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.228-234
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    • 1998
  • The aim of this paper is to study the characteristics of thermo-hydrodynamic lubrication in the bimetal bearings. Bimetal bearing is composed of lining and back metal. The THD model is proposed to calculate oil film temperature and pressure in the bimetal bearing. As results of analysis, comparative results of maximum bearing temperature are presented for the various materials and thickness of lining metal.

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Computation of Distortion Power Using Complex THD (THD의 복소 성분을 이용한 고조파 왜곡 환경에서의 전력 계산)

  • 최종욱;장길수
    • The Transactions of the Korean Institute of Electrical Engineers A
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    • v.53 no.7
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    • pp.389-396
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    • 2004
  • This paper introduces a new algorithm to calculate distortion power using complex THD(Total Harmonic Distortion) index. The proposed algorithm involves FFT(Fast Fourier Transform) to compute real and imaginary THDs of voltage and current. Case studies are presented to show the availability of the proposed method.

Design and Implementation of PFC and THD Reduction System for CFL Mulitple Connection (다중접속 CFL용 PFC 및 THD 감소 시스템의 설계 및 구현)

  • 박종연;조호찬;최원호
    • Proceedings of the IEEK Conference
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    • pp.67-70
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    • 2002
  • In this paper, we have researched a Automatic Power Factor Correction and THD reduction System for the multiple connection of CFL. Also in this paper, the power factor has been researched for the design of CFL, found the reason why the power factor is low and THD is too high. This paper has designed the PFC System for the multiple connection of CFL, and then we have increased the power factor and reduced the total harmonic distortion, by implementing them.

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