• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.49 no.7
• /
• pp.365-368
• /
• 2000

Traditionally, load flows have been calculated using the Gauss-Seidel and Newton-Raphson Method. DistFlow Method which is proposed by Wu and Baran is superior to the other two methods because it does not require the admittance matrix calculation to optimize the distribution system. This paper introduces a new alternative algorithm to the DistFlow Method which is slow and complex to find solutions as the number of lateral and sublateral increases. The proposed load flow method can construct System Jacobian easily. We can minimize the off-diagonal elements of the branch Jacobian and submatrices in the System Jacobian. Simulation results show that progressive performances of the proposed algorithm have a better convergence time.

• Proceedings of the KIEE Conference
• /
• 2000.07a
• /
• pp.43-45
• /
• 2000

Traditionally, load flows have been calculated using the Gauss-Seidel and Newton-Raphson Method. DistFlow Method which is proposed by Wu and Baran is superior to the other two methods because it does not require the admittance matrix calculation to optimize the distribution system. This paper introduces a new alternative algorithm to the DistFlow Method which is slow and complex to find solutions as the number of lateral and sublateral increases. The proposed load flow method can construct System Jacobian easily. We can minimize the off-diagonal elements of the branch Jacobian and submatrices in the System Jacobian. Simulation results show that progressive performances of the proposed algorithm.

• Proceedings of the KIEE Conference
• /
• 1998.07c
• /
• pp.918-922
• /
• 1998

With the development of industry, the qualitical advancement of power is needed. Since it is placed in the end step of power system, the fault at the distribution system causes some users blackout directly. So if the fault occurs, quick restoration is very important subject and, for the reason, induction of the distribution automation system is now being progressed briskly. For the quick restoration of the faulted distribution system, the load shedding of the blackout-area must be followed, and the other problems like the shedded load, faulted voltage and the rest may cause other accident. Accordingly load shedding must be based on the precise calculation technique during the distribution system load flow(dist flow) calculation. In these days because of its superior convergence characteristic the Newton-Raphson method is most widely used. The number of buses in the distribution system amounts to thousands, and if the fault occurs at the distribution system, the speed for the dist flow calculation is to be improved to apply to the On-Line system. However, Newton-Raphson method takes much time relatively because it must calculate the Jacobian matrix and inverse matrix at every iteration, and in the case of huge load, the equation is hard to converge. In this thesis. matrix equation is used to make algebraical expression and then to solve load flow equation and to modify above defects. Then the complex matrix is divided into real part and imaginary part to keep sparcity. As a result time needed for calculation diminished. Application of mentioned algorithm to 302 bus, 700 bus, 1004 bus system led to almost identical result got by Newton-Raphson method and showed constant convergence characteristic. The effect of time reduction showed 88.2%, 86.4%, 85.1% at each case of 302 bus, 700 bus system 86.4%, and 1004 bus system.

• Journal of the Korean Ceramic Society
• /
• v.23 no.1
• /
• pp.21-26
• /
• 1986

By the floating zone method with infrared radiation convergence type heater homogeneously $Cr^{3+}$ doped alu-mina single crystal was obtained. And sizx {1010} facets appeared at the surface of [0001] grown crystals. $ZrO_2$ and $HfO_2$ precipitated as secondary phase and were not doped in the crystals. We found that the dist-ribution of the secondary phase which was mainly located at the surface and the peripheral region was closely related to the flow pattern of melt zone.

• Proceedings of the KIEE Conference
• /
• 2003.07a
• /
• pp.387-389
• /
• 2003

This paper presents a application of the voltage analysis method for practical distribution system with DG(Distributed Generation). If the wind farm system is introduced in the existing distribution systems, there are many serious impacts in systems. So it is practiced the voltage analysis for the distribution system when the wind farm is introduced. in this paper, we used computer simulations with the DistFlow Method for system analysis.

• Proceedings of the KIEE Conference
• /
• 2003.11a
• /
• pp.181-183
• /
• 2003

본 연구에서는 현재 국내-외 논문을 참조하여 배전계통에 적용된 조류계산 알고리즘의 적용사례를 조사하였다. 배전계통에 적용된 조류계산알고리즘은 Power Summation Method와 Current Summation Method가 있다. 배전계통은 선로의 구조가 거의 대부분 방사상으로 성되어 있기 때문에 Newton Raphson, Gauss Seidel, Fast Decoupled 방법을 그대로 사용하기는 문제가 있다. 그래서 DistFlow, Forward/Backward sweeping 법 등이 주로 사용되어 왔다. 그러나 미래의 계통은 현재와는 또 다른 Topology로 방사상과 루프가 혼합된 형태로 다르게 구성되어야 할 것이다. 이러한 상황에서 미래의 배전계통에 대하여 적용 가능한 알고리즘을 전망하고져 한다.

• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.524-525
• /
• 2008

에너지 효율이 강조되는 요즘, 전력계통의 손실을 최소화시킬 수 있는 분산전원 최적 출력 운전은 에너지 효율 향상에 도움을 줄 것이다. 본 논문에서는 다수의 집중부하를 갖고 있는 방사형 배전계통에 분산전원이 연계됐을 때를 가정하였고 계통 해석을 위해 Dist Flow 방법을 이용하여 계통의 조류계산을 하였다. 분산전원의 최적 출력식을 증명을 통해 도출하였고 시뮬레이션 프로그램 PSCAD /EMTDC으로 검증하여 보았다. 또한 최적 출력을 통해서 전압 profile이 향상되는 것을 볼 수 있었다.

• Journal of Korea Water Resources Association
• /
• v.49 no.8
• /
• pp.645-656
• /
• 2016

The study performed a regional flood frequency analysis and proposed a regression equation to estimate design floods corresponding to return periods for ungauged basins in Geum-river basin. Five preliminary tests were employed to investigate hydrological independence and homogeneity of streamflow data, i.e. the lag-one autocorrelation test, time homogeneity test, Grubbs-Beck outlier test, discordancy measure test ($D_i$), and regional homogeneity measure (H). The test results showed that streamflow data were time-independent, discordant and homogeneous within the basin. Using five probability distributions (generalized extreme value (GEV), three-parameter log-normal (LN-III), Pearson type 3 (P-III), generalized logistic (GLO), generalized Pareto (GPA)), comparative regional flood frequency analyses were carried out for the region. Based on the L-moment ratio diagram, average weighted distance (AWD) and goodness-of-fit statistics ($Z^{DIST}$), the GLO distribution was selected as the best fit model for Geum-river basin. Using the GLO, a regression equation was developed for estimating regional design floods, and validated by comparing the estimated and observed streamflows at the Ganggyeong station.