• 한국유체기계학회 논문집
• /
• 제12권3호
• /
• pp.38-43
• /
• 2009

The Shiwhaho is an artificial lake located in Yellow sea of Korea where the ocean tidal current is significantly strong, and the tidal power plant is currently being under construction to generate electric power from the ocean tidal current. In addition to the tidal power plant under construction, an ocean current power park was proposed to maximize the power generation by utilizing the ocean current generated by the tidal power plant. To evaluate the feasibility of such combined power plant, the flow characteristics in the ocean current power parks connected with the tidal power plants were investigated numerically in the present study. When two different type of generations are operating together as a system, their interference may occur, which affects their efficiency. Therefore, the minimum distances between the tidal power plants and the ocean current power generators are studied in the present study to minimize such interference. The feasible region to generate power around the Shiwha tide embankment is also predicted by considering predicted ocean current speed distribution. Various arrangements of the ocean current generators are examined and an optimal arrangement is also discussed.

• 대한전기학회논문지
• /
• 제45권4호
• /
• pp.543-552
• /
• 1996

The goal of this paper is to developed a DSP based power analyzing and control system by 3-Dimensional (3-D) space current co-ordinates. A developed system is made up of 486-PC and DSP (Digital Signal Processor) board, Active Power Filter, Non-linear thyristor load, and Power analyzing and control program for Windows. Power is analyzed using signal processing techniques based on the correlation between voltage and current waveforms. Since power analysis algorithm is performed by DSP, power analysis is achieved in real-time even under highly dynamic nonlinear loading conditions. Combining control algorithm with power analysis algorithm is performed by DSP, power analysis is achieved in real-time even under highly dynamic nonlinear loading conditions. Combining control algorithm with power analysis algorithm, flexibility of the proposed system which has both power analysis mode and control mode, is greatly enhanced. Non-active power generated while speed of induction motor is controlled by modulating firing angle of thyristor converter, is compensated by Active Power Filter for verifying a developed system. Power analysis results, before/after compensation, are numerically obtained and evaluated. From these results, various graphic screens for time/frequency/3-D current co-ordinate system are displayed on PC. By real-time analysis of power using a developed system, power quality is evaluated, and compared with that of conventional current co-ordinate system. (author). refs., figs. tabs.

• 전력전자학회논문지
• /
• 제27권2호
• /
• pp.92-99
• /
• 2022

Due to space and geographical constraints, the power source may be located outside the island area, resulting in the considerable length of transmission line. In these cases, when an active power is transmitted, unexpected reactive power is generated at a point of common coupling (PCC). Unlike the power transmitted from the power generation source, the reactive power adversely affects the system. This study proposes a new algorithm that controls reactive power at PCC. Causes of reactive power errors are separated into parallel and series components, which allows the algorithm to compensate the reactive current of the inverter output and control reactive power at the PCC through calculations from the impedance, voltage, and current. The proposed algorithm has economic advantages by controlling the reactive power with the inverter of the power source itself, and can flexibly control power against voltage and output variations. Through the simulation, the algorithm was verified by implementing a power source of 3 [kVA] capacity connected to the low voltage system and of 5 [MVA] capacity connected to the extra-high voltage system. Furthermore, a power source of 3 [kVA] capacity inverter is configured and connected to a mock grid, then confirmed through experiments.

• Journal of Power Electronics
• /
• 제6권4호
• /
• pp.290-297
• /
• 2006

Various methods have been discussed to reduce detent force in a tubular permanent magnet type linear single phase AC generator. In particular, the proposed methods depend on variations of the permanent magnet construction. These methods include two approaches in the form of sloped magnets, and conical magnets in addition to the conventional method of optimizing the magnet length. The undesired detent force ripples were calculated by a two dimensional Finite Element Method (FEM). Moreover, the generated electromotive force in the stator coils was calculated for each configuration of the permanent magnet. The experimental results agreed well with those obtained from the FEM-based simulations. Sufficient reduction in the detent force was achieved over the range of 40% while the root mean square of the output voltage was maintained. It was found that sloping the permanent magnet decreased the detent force and at the same time increased the generated rms voltage of the AC generator. The performance of the designed linear AC generator was evaluated in terms of its efficiency, total weight, losses, and power to weight ratio.

• 한국수정란이식학회지
• /
• 제23권3호
• /
• pp.203-209
• /
• 2008

To estimate the genetic characteristics and cumulative power of discrimination (CPD) existing among Hanwoo (Korean cattle) and exotic foreign population (Angus, Herford, Charolais, Holstein) we used a total of 414 genomic DNAs from five breeds population (Hanwoo, Angus, Hereford, Charolais, Holstein). Genetic characteristics indices including mean allele number among loci, unbiased heterozygosity ($h_i$) within locus and polymorphic information content (PIC) and unbiased average heterozygosity (H) among loci in four breeds were calculated using the generated allele frequencies by each marker. The mean allele numbers for all loci ranged between 5 and 7 while heterozygosity (H) ranged from 0.75 (HW) to 0.64 (HF) among loci and across breeds heterozygosity (H) was 0.69. The generated unbiased average heterozygosity among loci in each breed was integrated to the global formula of CPD resulting in 99.71 % within the populations. The genetic variation of HW (Hanwoo) showed highest estimates among the analyzed breeds.

• 한국전기전자재료학회논문지
• /
• 제11권11호
• /
• pp.1035-1042
• /
• 1998

After the 1990's, a computer-aided partial discharge(PD) measurement system was referred in part of aging diagnosis using digital signal processing as the new technology has been studied. The PD patterns and relevant information for pattern recognition are discussed in PD research area, because discharge quantity(q), the number of discharge pulse(n) and the applied boltage phase($\varphi$) was combined with the system information of the aging state. This paper investigates the discharge phase and quantity, as well as the number of discharge(n) with regard to discharge signals generated in power cable. therefore, according to characteristic analysis on the distribution of $\varphi$, q and n, it is able to apply in the aging analysis of power cable which visual observation is impossible and distribution change of discharge signals offers much information for risk degree on aging progress of insulation materials.

• 한국정보통신학회논문지
• /
• 제3권2호
• /
• pp.447-453
• /
• 1999

In MHD power generation system, enthalpy of the working gas is convened to electric power directly through expansion in generator channel. It means that electric power can be generated without a moving mechanical linkage such as turbine blades. The principle of MHD generation is based on Faraday'law of induction that eletromotive force(u$\times$B) is generated when the working gas of velocity u flows a channel in which magnetic field of strength(B) exists. In this paper, helium gas seeded with cesium is used as working gas. There are two types of generator in MHD generation; linear type faraday and disk type hall generator. Rogowski coils having the bandwidth of the 100(Hz) ~ 20(kHz) were used for measuring current flowing MHD disk channel. Optimum load resistor value of the MHD generator studied was 2.5[$\Omega$]. Disk type hall generator's generation performance is the main target of this paper, which superiors to linear type Faraday generator in many points. Isentropic efficiency and enthalpy extraction rate of disk type shock tube driven hall generator is discussed here.

• 전력전자학회논문지
• /
• 제7권3호
• /
• pp.262-271
• /
• 2002

견인전동기 구동시스템에 사용되는 PWM 인버터는 전력용량이 크기 때문에 스위칭주파수가 제한되며, 따라서 전자기적 가청소음이 발생한다. 이러한 가청소음을 줄이기 위하여 새로운 MRSF-PWM 방식을 제안한다. 제안한 MRSF-PWM 방식에서는 고조파를 확산시키기 위해 삼각파와 톱니파를 함께 운송파로 사용하며, 출력전압의 선형제어범위를 넓히기 위해 정현파에 3차 고조파를 주입한 파형을 기준파로 사용한다. MRSF-PWM 방식의 타당성을 검증하기 위하여 컴퓨터 시뮬레이션을 수행하였다. 그 결과, MRSF-PWM 방식이 선형성 및 고조파 확산면에서 다른 RPWM 방식보다 우수하며 가청소음 저감면에서 SPWM 방식보다 효과적임을 확인하였다.

• Journal of Electrical Engineering and Technology
• /
• 제12권5호
• /
• pp.2001-2006
• /
• 2017

This paper explains the effects of the weak signal of a rotating-type electric field mill sensor fabricated for measuring the intensity of the electric field generated by high-voltage direct current (HVDC) power transmission lines. The fabricated field mill consists of two isolated electrode vanes, a motor driver, and a ground part. The sensor plate is exposed to and shielded from the electric field by means of a rotary shutter consisting of a motor-driven mechanically complementary rotor/stator pair. When the uncharged sensor plate is exposed to an electric field, it becomes charged. The rotating electrode consists of several conductive vanes and is connected to the ground part, so that it is shielded. Determining the appropriate design variables such as the speed of the vane, its shape, and the distance between the two electrodes, is essential for ensuring optimal performance. By varying the speed, the weak signal characteristics which is used to signal processing and calibration experiment are quite different. Each weak signal pattern was analyzed along with the output voltage characteristics, in order to be able to determine the intensity of the electric field generated by HVDC power transmission lines with accuracy.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
• /
• pp.220-221
• /
• 2006

This paper presents a single-phase parallel active power filter with an analog control circuit to eliminate for harmonic source currents generated by nonlinear loads. The proposed system removes the harmonic source currents by injecting a compensation current that is 180' out of phase with the load harmonic current. The detection of the load harmonics is realized by a simple new structure, referred to the Notch Filter with GIC (Generalized Impedance Converter), which has higher Q than existing harmonic detecters and a simpler structure. The compensation current is obtained using the proposed harmonic detection circuit, DC-Link voltage, and output current of the full-bridge inverter controlled current mode PWM controller. The operation of the proposed system is verified experimentally.