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20kV MVDC 급 방사형 배전계통의 보호협조 운용알고리즘에 관한 연구
이후동,태동현,노대석,김주용 대한전기학회 2020 전기학회논문지 Vol.69 No.6
Recently, MVDC(medium voltage direct current) distribution system has been interested worldwide due to introduction of renewable energy sources, an increase of DC load and customer’s demands for high quality and high reliability of the power system. Although these MVDC systems have technologies to improve and modernize the performance of the distribution system with high reliability, high flexibility and high efficiency, they have faced challenges and difficulties in the early stages of research and development. In particular, since power converter devices to supply DC sources have extremely high sensitivity, protection method of the MVDC distribution system is being required in order to protect and operate the MVDC system in a stable manner. Therefore, this paper proposes operation algorithm of protection coordination in MVDC distribution system to rapidly separate fault sections by using slope characteristics of fault currents and presents prevention method for shutdown of the main power source based on the CLR(current limit resistor). And also, this paper performs modeling of 20kV MVDC distribution system which are composed of substation, main and section converter based on the PSCAD/EMTDC S/W. From the simulation results of fault characteristics the at primary and secondary side in MVDC, it is confirmed that the main converter in primary feeder cannot be shutdown due to keeping fault currents within allowable limits of main converter, if the proper capacity of the CLR is installed at secondary side of section converter. In addition, it is found that the proposed method can separate outage sections in primary feeder and minimize them, if slope ranges of fault current are properly determined at each protection section.
녹음 환경의 차이에 따른 화자의 음원 특성 비교 : 발성유형지수 k를 중심으로
이후동,강선미,박한상,장문수 한국음성과학회 2003 음성과학 Vol.10 No.3
Spoken sound includes not only speaker's source but the characteristics of vocal tract and speech radiation. This paper is based on the theory of Park[1], who proposes the Phonation Type Index k; a variable that shows the characterisic of speaker's source excluding those of speaker's vocal tract and speech radiation. With Park's theory, we collect data by changing recording environments and expanding experimental data, and analyze the data collected to see whether or not the PTI k shows good discriminating power as a variable for speaker recognition. In the experiment, we repeatedly record 8 sentences ten times for each of 5 males in the environment of a recording room and an office, extract PTI k for each speaker, and measure the discriminating power for each speaker by using the value of PTI k. The result shows that PTI k has the excellent discriminating power of speakers. We also confirm that, even if the recording environment is changed, PTI k shows similar results.
숫자음의 스펙트럼 차이값과 상관계수를 이용한 화자인증 파라미터 연구
이후동,강선미,장문수,양병곤 한국음성과학회 2004 음성과학 Vol.11 No.3
Speaker identification system basically functions by comparing spectral energy of an individual production model with that of an input signal. This study aimed to develop a new speaker identification system from two parameters from the spectral energy of numeric sounds: difference sum and correlation coefficient. A narrow-band spectrogram yielded more stable spectral energy across time than a wide-band one. In this paper, we collected empirical data from four male speakers and tested the speaker identification system. The subjects produced 18 combinations of three-digit numeric sounds ten times each. Five productions of each three-digit number were statistically averaged to make a model for each speaker. Then, the remaining five productions were tested on the system. Results showed that when the threshold for the absolute difference sum was set to 1200, all the speakers could not pass the system while everybody could pass if set to 2800. The minimum correlation coefficient to allow all to pass was 0.82 while the coefficient of 0.95 rejected all. Thus, both threshold levels can be adjusted to the need of speaker identification system, which is desirable for further study.
이후동,이영진,이성희 한국지리정보학회 2022 한국지리정보학회지 Vol.25 No.4
Recently, the forests in Korea have acumulated damage due to continuous forest disasters, and the ned for technologies to monitor forest managements is being isued. The size of the afected area is large terain, technologies using drones, artificial inteligence, and big data are being studied. In this study, a standard dataset were conducted to develop an algorithm that automaticaly detects suspicious tres damaged by forest pests using dep learning and drones. Experiments using the YOLO model among object detection algorithm models, the YOLOv4-P7 model showed the highest recal rate of 69.69% and precision of 69.15%. It was confirmed that YOLOv4-P7 should be used as an automatic detection algorithm model for tres suspected of being damaged by forest pests, considering the detection target is an ortho-image with a large image size.
20kV급 방사형 MVDC 배전계통의 보호협조 운용알고리즘에 관한 연구
이후동(Hu-Dong Lee),태동현(Dong-Hyun Tae),노대석(Dae-Seok Rho),김주용(Ju-Yong Kim) 대한전기학회 2020 전기학회논문지 Vol.69 No.6
Recently, MVDC(medium voltage direct current) distribution system has been interested worldwide due to introduction of renewable energy sources, an increase of DC load and customer’s demands for high quality and high reliability of the power system. Although these MVDC systems have technologies to improve and modernize the performance of the distribution system with high reliability, high flexibility and high efficiency, they have faced challenges and difficulties in the early stages of research and development. In particular, since power converter devices to supply DC sources have extremely high sensitivity, protection method of the MVDC distribution system is being required in order to protect and operate the MVDC system in a stable manner. Therefore, this paper proposes operation algorithm of protection coordination in MVDC distribution system to rapidly separate fault sections by using slope characteristics of fault currents and presents prevention method for shutdown of the main power source based on the CLR(current limit resistor). And also, this paper performs modeling of 20kV MVDC distribution system which are composed of substation, main and section converter based on the PSCAD/EMTDC S/W. From the simulation results of fault characteristics the at primary and secondary side in MVDC, it is confirmed that the main converter in primary feeder cannot be shutdown due to keeping fault currents within allowable limits of main converter, if the proper capacity of the CLR is installed at secondary side of section converter. In addition, it is found that the proposed method can separate outage sections in primary feeder and minimize them, if slope ranges of fault current are properly determined at each protection section.