• Title/Summary/Keyword: High frequency injection

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Scheme for Reducing Harmonics in Output Voltage of Modular Multilevel Converters with Offset Voltage Injection

  • Anupom, Devnath;Shin, Dong-Cheol;Lee, Dong-Myung
    • Journal of Power Electronics
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    • v.19 no.6
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    • pp.1496-1504
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    • 2019
  • This paper proposes a new THD reduction algorithm for modular multilevel converters (MMCs) with offset voltage injection operated in nearest level modulation (NLM). High voltage direct current (HVDC) is actively introduced to the grid connection of offshore wind powers, and this paper deals with a voltage generation technique with an MMC for wind power generation. In the proposed method, third harmonic voltage is added for reducing the THD. The third harmonic voltage is adjusted so that each of the pole voltage magnitudes maintains a constant value with a maximum number of (N+1) levels, where N is the number of sub-modules per arm. By using the proposed method, the THD of the output voltage is mitigated without increasing the switching frequency. In addition, the proposed method has advantageous characteristics such as simple implementation. As a part of this study, this paper compares the THD results of the conventional method and the proposed method with offset voltage injection to reduce the THD. In this paper, simulations have been carried out to verify the effectiveness of the proposed scheme, and the proposed method is implemented by a HILS (Hardware in the Loop Simulation) system. The obtained results show agreement with the simulation results. It is confirmed that the new scheme achieved the maximum level output voltage and improved the THD quality.

Property of Long vertical rod according to the different injection point with impulse current (대형 봉상 접지전극의 임펄스 인가위치에 따른 특성)

  • 이복희;장근철;엄주홍;김병근;오성균;길형준
    • Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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    • 2003.11a
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    • pp.369-372
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    • 2003
  • To obtain a low ground resistance in high resistivity soil or in insufficient place such as downtown, long vertical ground rods are often used. However, if the lightning current or fault current with high frequency flows into the grounding system, the ground impedance is remarkedly increased. This paper presents how the impulse and fault current works on the long. vertical ground rods associated with incoming points. When the test current was injected at the bottom of ground rod, the potential waveform of ground rod includes the oscillation with high frequency.

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Sensorless Operation of Low-cost Inverters through Square-wave High Frequency Voltage Injection (사각 고주파 주입을 통한 저가형 인버터의 센서리스 운전)

  • Hwang, Sang-Jin;Lee, Dong-Myung
    • Journal of IKEEE
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    • v.26 no.1
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    • pp.95-103
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    • 2022
  • In this paper, the efficiency of a sensorless method with square-wave injection for a low-cost inverter, so called B4 inverter is presented. This inverter comprises only 4 switches to reduce system cost. It is distinguished from the conventional B6 inverter that has 6 of switching elements. The B4 inverter, injected a 1 kHz of harmonic wave, has been modelled using the functions and library in Matlab/Simulink. This paper described each component of sensorless algorithm. Among them, the Notch Filter is used to extract the harmonic component of the phase current and a second-order low-pass filter was used to reduce the ripple of the estimated speed. It is shown through simulation that the rotor angle of a permanent magnet synchronous motor is detected by multiplying the current waveform extracted using the notch filter by the harmonic voltage. The feasibility of the proposed method is shown through Simulink simulation.

An experimental study on the effect of mass injection location and flow rate for tip vortex cavitation of 3D hydrofoil (수중익 날개 끝 보텍스 캐비테이션 제어를 위한 질량분사 위치 및 분사량 영향에 대한 실험적 연구)

  • Eunsue Hwang;So-Won Jeong;Hongseok Jeong;Hanshin Seol
    • The Journal of the Acoustical Society of Korea
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    • v.42 no.3
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    • pp.233-242
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    • 2023
  • In this paper, the effect of mass injection on the control of tip vortex cavitation was studied experimentally. A mass injection system for a 3D hydrofoil was designed to control the location of injection as well as the injection rate. A series of cavitation tests were carried out in a cavitation tunnel for different injection locations and rates. The cavitation behaviour was observed using a high-speed camera and the corresponding noise was measured using a hydrophone installed in the observation window. The results showed that the tip vortex cavitation was suppressed under certain conditions and the noise was reduced in some frequency bands. It was also found that there is a location where the effect of mass injection could be maximized and hence the noise reduction.

CMOS Integrated Multiple-Stage Frequency Divider with Ring Oscillator for Low Power PLL

  • Ann, Sehyuk;Park, Jusang;Hwang, Inwoo;Kim, Namsoo
    • Transactions on Electrical and Electronic Materials
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    • v.18 no.4
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    • pp.185-189
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    • 2017
  • This paper proposes a low power frequency divider for an integrated CMOS phase-locked loop (PLL). An injection-locked frequency divider (ILFD) was designed, along with a current-mode logic (CML) frequency divider in order to obtain a broadband and high-frequency operation. A ring oscillator was designed to operate at 1.2 GHz, and the ILFD was used to divide the frequency of its input signal by two. The structure of the ILFD is similar to that of the ring oscillator in order to ensure the frequency alignment between the oscillator and the ILFD. The CML frequency divider was used as the second stage of the divider. The proposed frequency divider was applied in a conventional PLL design, using a 0.18 ${\mu}m$ CMOS process. Simulation shows that the proposed divide-by-two ILFD and the divide-by-eight CML frequency dividers operated as expected for an input frequency of 1.2 GHz, with a power consumption of 30 mW.

Local Heating of an Injection Mold using Selective Induction Heating (선택적 유도가열을 사용한 사출금형의 국부가열기술)

  • Do, Bum-Suk;Park, Jung-Min;Eom, Hye-Ju;Park, Keun
    • Proceedings of the KSME Conference
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    • 2008.11a
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    • pp.1119-1123
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    • 2008
  • High-frequency induction is an efficient way to heat mold surface by electromagnetic induction in a noncontact procedure. It has been recently applied to the injection molding of thin-walled parts or micro/nano structures. Though the induction heating has an advantage in terms of its rapid-heating capacity on the mold surface, it still has difficulty in efficient mold temperature control due to the restriction of an induction coil design suitable for the given mold shape. The present study proposed a localized mold heating method by means of selective use of mold material. For localized induction heating, an injection mold composed of ferromagnetic material and paramagnetic material is used. The electromagnetic induction concentrates on the ferromagnetic material, from which we can selectively heat for the local mold elements. The feasibility of the proposed heating method is investigated through an experimental measurement in terms of the heating efficiency on the localized mold surface.

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Study for Related Mechanism of Anti-Inflammatory Effect Induced by Neddle electrode electrical stimulation in Mouse Air Pouch Model. (Mouse Air Pouch Model에서 침전극 저주파치료로 유도된 소염 작용에 관한 연구)

  • Chung, Jin-Woo;Hwang, Hyun-Sook;Lim, Jong-Soo
    • Journal of Korean Physical Therapy Science
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    • v.9 no.2
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    • pp.111-122
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    • 2002
  • In oriental medicine, manual-acupuncture and electroacupuncture (EA) have been widely utilized to cure several inflammatory diseases such as arthritis. We designed this experiment to find neurochemical mechanism related to electroacupuncture induced anti-inflammatory effect on mouse air pouch model. EA with both low frequency (1 Hz) and high frequency (120 Hz) was treated after induction of inflammation in air pouch using injection of zymosan. To verify the role of opioid system in electroacupuncture-induced anti-inflammatory effect, naloxone (10 mg/kg) was pretreated. In addition, idazoxan (5 mg/kg) was pre-treated to evaluate the possible effect of endogenous adrenergic system in autonomic system on EA induced anti-inflammatory effect. As results of this study, naloxone pretreatment did not change the anti-inflammatory effect evoked by high frequency EA, while low frequency EA(1 Hz) induced anti-inflammatory effect was dramatically suppressed by naloxone pretreatment. These data indicated that endogenous opioid system might be extensively involve in anti-inflammatory effect evoked by not high frequency, but low frequency EA. However, idazoxan pretreatment did not produce any modulatory effect on both low and high frequency EA induced anti-inflammatory effect, suggesting that EA induced anti-inflammatory effect was not mediated by endogenous adrenergic system. In conclusion, these data strongly suggested that EA induced anti-inflammatory effect is mediated by endogenous opioid system, not endogenous adrenergic system.

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A Study on the Nurse's Recognition and Performance in Intravenous Therapy Management (간호사의 정맥주사 관리에 대한 인식과 수행에 관한 연구)

  • Kim Myung-Hee;Kim Youn-Hwa
    • Journal of Korean Academy of Fundamentals of Nursing
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    • v.5 no.2
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    • pp.207-224
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    • 1998
  • The purposes of this study were to identify nurse's recognition and performance and to represent the factors of hindrance in the IV therapy management. The subjects were 420 nurses who worked at five general hospitals in Pusan. Tha data were collected using a questionnaire and the period of data collection was from January 1 to January 31, 1998. The instrument for this study was made by author oneself on the basis of guidelines Simmons et al', CDC' Stanley' and Kurdi' guideline, Cllinical Nurse's Association' that consist of 68 items for 5 fields ; pre-injection, just before-injection, needle-injection, during injection, post-injection field. Cron-bach Alpha coefficient of recognition and performance in the IV therapy management was .93 and .87. The datas were analized by a SPSS program using frequency, percent, paired t-test, t-test and oneway ANOVA. The results obtained were as follows : 1. The mean score of recognition in IV therapy management was significantly higher than that of performance(t=5.86, P<.001). 2. The items of lower than mean score of each fields in performance were the identification of drugs, hands washing, patient teaching about medication, disinfectional methods of the injection site and the rubber stopper in bottle, the use of disposable gloves, mask and eye goggles at the chemotherapy preparation, use of tape and armboard, changing the IV tubing, labeling the dressing over the injection site, observation and recordings of patient's condition after medication and confirmation of the needle length at the needle removal. 3. The factors of hindrance in IV therapy were 'having no time', 'insufficiency of goods', 'unknowing of methods', 'no disadvantage', and 'factors of doctor's doing'. The most important factor was 'have no time', especially item of hands washing. The other factors of hindrance showed high frequency in the following items ; 'insufficiency of goods' in the use of disposable gloves, mask and eye goggles at the chemotherapy preparation, 'unknowing of methods' in the certification of drugs compatibility, 'no disadvantage' in the labeling the dressing over the injection site, and 'factors of doctor's doing' in the changing the subclavian catheter dressing and checking the glucose level during the TPN infusion. In conclusion, there is necessity of educational program which can improve the nurse's knowledge of drugs, disinfection methods, comfort of patient and recordings in IV therapy management and alternative plan which are political and financial aids such as setting up the sink, giving of paper towels and necessary goods in the IV therapy for reducing the factors of hindrance for IV therapy management.

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Effects of Electroacupuncture on Memory Modulation (전기 침 자극의 기억 조절 효과)

  • Lee, Sang-Kwan;Kim, Min-Soo;Ahn, Ryun-Sup;Kim, Moon-Soo;Sung, Kang-Keyng
    • Journal of Physiology & Pathology in Korean Medicine
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    • v.21 no.6
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    • pp.1543-1548
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    • 2007
  • Recent experiments investigating the analgesic or anti-stress effects of electro-acupuncture provide extensive evidence that opioid or stress hormone system is involved in those effects, respectively. It has been also suggested that opioid or stress hormones modulate long-term memory consolidation or retrieval in animals and human subjects. This article reviews the possibilitythat electroacupuncture can modulate memory consolidation or retrieval. The release of serum cortisol is enhanced or reduced by high-frequency or low-frequency electroacupuncture, respectively. Also the release of beta endorphin and enkephalin is enhanced by low-frequency electroacupuncture and the release of dynorphin is enhanced by high-frequency electroacupunture. The memory consolidation is enhanced by post-training injection of Glucocorticoids, Naloxone or Dynorphin. So this review suggests strongly that memory consolidation can be modulated by electroacupuncture.

Enhancement of Signal to Noise Ratio for High Frequency Square-Wave Injection Sensorless Drive with Regulation of Induced High Frequency Current Ripple (고주파 전류 맥동 제어를 통한 신호 주입 센서리스 방법의 신호 대 잡음 비(SNR) 개선)

  • Kim, DongOuk;Kwon, Yong-Cheol;Sul, Seung-Ki
    • Proceedings of the KIPE Conference
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    • 2013.11a
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    • pp.167-168
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    • 2013
  • 신호 주입 센서리스 구동 시, 인버터의 비선형성으로 인한 주입 전압 왜곡현상은 전류 신호 정보의 SNR을 떨어뜨리게 된다. 이로 인하여 회전자 위치를 추정하는 과정에서 오차가 발생하는 문제점이 발생한다. 본 논문에서는 인버터의 비선형성이 주입 전압에 미치는 영향을 분석하고, 전류 신호 정보의 SNR을 개선하기 위하여 고주파 전류 맥동의 크기를 일정하게 제어하는 주입 전압을 인가하는 방법을 제안한다. 실험을 통하여, 제안된 방법의 성능을 검증하였다.

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