• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.158-161
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• 1990

Recently, the phenomena of voltage instability have become major concern in power system. These phenomena are closely related to what are called multiple load flow solutions and calculation methods on these solutions have developed. But conventional methods require much run time. In this paper, by using sign of |J| and weighting factor considering system configuration, fast calculation method on the multiple load flow solutions is presented.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.311-315
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• 1998

Load Flow calculation methods can usually be divided into Gauss-Seidel method, Newton-Raphson method and decoupled method. Load flow calculation is a basic on-line or off-line process for power system planning, operation, control and state analysis. These days Newton-Raphson method is mainly used since it shows remarkable convergence characteristics. It, however, needs considerable calculation time in construction and calculation of inverse Jacobian matrix. In addition to that, Newton-Raphson method tends to fail to converge when system loading is heavy and system has a large R/X ratio. In this paper, matrix equation is used to make algebraic expression and then to solve load flow equation and to modify above defects. And it preserve certain part of Jacobian matrix to shorten the time of calculation. Application of mentioned algorithm to 14 bus, 39 bus, 118 bus systems led to identical result and the number of iteration got by Newton-Raphson method. The effect of time reduction showed about 28%, 30%, at each case of 39 bus, 118 bus system.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.48 no.9
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• pp.1081-1087
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• 1999

Load Flow calulation methods can usually be divided into Gauss-Seidel method, Newton-Raphson method and decoupled method. Load flow calculation is a basic on-line or off-line process for power system planning. operation, control and state analysis. These days Newton-Raphson method is mainly used since it shows remarkable convergence characteristics. It, however, needs considerable calculation time in construction and calculation of inverse Jacobian matrix. In addition to that, Newton-Raphson method tends to fail to converge when system loading is heavy and system has a large R/X ratio. In this paper, matrix equation is used to make algebraic expression and then to slove load flow equation and to modify above defects. And it preserve P-Q bus part of Jacobian matrix to shorten computing time. Application of mentioned algorithm to 14 bus, 39 bus, 118 bus systems led to identical results and the same numbers of iteration obtained by Newton-Raphson method. The effect of computing time reduction showed about 28% , 30% , at each case of 39 bus, 118 bus system.

• Proceedings of the KIEE Conference
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• 1997.07c
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• pp.1074-1077
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• 1997

Newton-Raphson method is mainly used since it shows remarkable convergence characteristics. It, however, needs considerable calculation time in construction and calculation of inverse Jacobian matrix. In this paper a new type of load flow equation is summarized as follows: Since inverse calculation of Jacobian matrix is not needed in the suggested algorithm but using complex bus voltage, the calculation process is simple. With the simple structure, reduction of calculation time is achieved.

• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.432-434
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• 1997

In order to find the steady-state operating condition of HVDC system interacting with AC power system, the load flow calculation of AC/HVDC system is performed. For the calculation, each generating unit is modeled by an equivalent voltage source and coupled impedance. The rectifier station is modeled by a controlled DC voltage source. EMTP simulation of the AC/HVDC system is also performed to verify the result of the load flow calculation.

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

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.78-80
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• 2005

The load flow calculation is one of the most critical issues in electrical power systems. Generally, load flow has been calculated by Gauss-Seidel method and Newton-Raphson method but these methods have some problems such as non-convergence due to heavy load and initial value. In this paper, to overcome such problems, the power flow is calculated by genetic algorithm. At the heavy load, the solution for problem can not be obtained by the Newton-Raphson method. However, it can be solved in case of using genetic algorithm. In this paper, the strong point of this method would be demonstrated in application to an example system.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.4
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• pp.201-206
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• 2003

Power system is analyzed by three methods of load flow, fault calculation, and voltage stability. Among there, load flow is calculated to flow of power in power in system at steady state. But, load flow is difficult to analyze to flow of power in substation, because power flow frequently alter by various equipments such as circuit bleaker, disconnect switch and shunt reactor. Particular, in 765[㎸] system, because of form of 1.5GB for stable operation, structure of substation has been very complex. In this paper, we describe technique for application of load flow algorithm in simulator for 765[㎸] substation. For this technique, we built each database for various equipments and considered form of 1.5GB Data as form of bus and line, for application of load flow, are acquired from built database, and then calculate load flow in substation. And. results of load flow are outputted in screen of operator console program.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.168-169
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• 2011

The aim of this paper is to present a new algorithm for the load flow problem using modified Newton-Raphson (NR) iteration method and a approach to derive a simple formula to compensate the reactive power at some heavy load bus. The reactive power source used in this research is the DG which is adjacent to the heavy load. Phenomena of low voltages may cause the load flow calculation process to diverge. In modified NR method, low voltages will be detected and corrected before the next iteration. Therefore, the results of load flow calculation process satisfy the voltage constraint i.e. higher than the lower voltage limit or higher than the critical voltage in case the conventional load flow diverges. Linearizing the power network using PTDFs is a simple method with accepted errors. A new value of voltage at the DG terminal is computed in terms of the voltage deviation of load buses. In this approach, solving the entire system is unnecessary.

• Journal of Korean Society of Water and Wastewater
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• v.30 no.3
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• pp.225-231
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• 2016

Peak load rate(i.e., maximum daily flow/average daily flow) has not been considered for industrial water demand planning in Korea to date, while area unit method based on average daily flow has been applied to decide capacity of industrial water treatment plants(WTPs). Designers of industrial WTPs has assumed that peak load would not exist if operation rate of factories in industrial sites were close to 100%. However, peak load rates were calculated as 1.10~2.53 based on daily water flow from 2009 to 2014 for 9 industrial WTPs which have been operated more than 9 years(9-38 years). Furthermore, average operation rates of 9 industrial WTPs was less than 70% which means current area unit method has tendency to overestimate water demand. Therefore, it is not reasonable to consider peak load for the calculation of water demand under current area unit method application to prevent overestimation. However, for the precise future industrial water demand calculation more precise data gathering for average daily flow and consideration of peak load rate are recommended.