• Proceedings of the KIEE Conference
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• 1992.07a
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• pp.205-210
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• 1992

The power flow calculations are the most important and powerful tools in the various studies of power system engineering. Newton-Raphson method, among the various power flow calculation techniques, is normally used due to its rapidness of numerical convergency. In the conventional Newton-Raphson method, however, there are some unrealistic assumptions, in which all the system power losses are considered to be supplied by the slack bus generator. Introducing the system power loss formula and augmenting the conventional Newton-Raphson power flow method, we can relieve the unrealistic assumption and improve the performance of power flow calculation. In this study, A new approach for handling the losses and augmenting the conventional power flow problem is proposed. The proposed method estimates the increamental changes of active power on each generation bus with respect to the change of total system power losses and the estimated value are used to update the slack bus power. If some studies for more theoritical investigations and verifications are followed, the proposed approach will show some improvement of the conventional method and give lots of contribution to increase the performance of power flow techniques in power systems engineering.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.19-23
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• 2003

This paper presents a new concept of reactive reserve based contingency constrained optimal power flow (RCCOPF) for voltage stability enhancement. This concept is based on the fact that increase in reactive reserves is effective for enhancement of voltage stability margins of post-contingent states, in this paper, the proposed algorithm is applied to voltage stability margin of interface flow. Interface flow limit, in the open access environment, can be a main drawback. RCCOPF for enhancement of interface flow margin is composed of two modules, modified continuation power flow (MCPF) and optimal power flow (OPF). These modules art recursively perform ed until satisfying the required margin of interface flow in the given voltage stability criteria.

• 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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• 2000.07a
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• pp.46-48
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• 2000

Continuation power flow has been developed to remove the ill-condition problem caused by singularity of power flow Jacobian at and near steady-state voltage instability point in conventional power flow. When solving large-scale power transmission systems, an alternative strategy for improving computational efficiency and reducing computer storage requirements is the decoupled power flow method, which makes use of an approximate version of the Newton-Raphson procedure. This paper presents a technique to improve the speed of continuation power flow system using decoupled power flow method.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.417-419
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• 2005

This paper presents the effects and the regional power distribution of an increase or a decrease of a power reserve by load flow calculations under seasonal load patterns of each country for the future power shortages faced by the metropolitan areas or by the southeastern area of the South Korea in North-East Asia. In these connections, the types of a power transmission for interconnection consist of the 765kV HVAC and the HVDC. In this paper, the various cases of the power system interconnections in Far-East Asia are presented, and the resulting interconnected power systems are simulated by means of a power flow analysis performed with the PSS/E 28 version tool. The power flow map is drawn from data simulated and the comparative study is done. In this future, a power flow analysis will be considered to reflect the effects of seasonal power exchanges And the plan of assumed scenarios will be considered with maximum or minimum power exchanges during summer or winter in North-East Asia countries.

• Journal of Electrical Engineering and Technology
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• v.9 no.4
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• pp.1137-1144
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• 2014

A parallel-feeding AC traction power system increases the power supply capacity and decreases voltage fluctuations, but the circulating power flow caused by the phase difference between the traction substations prevents the system from being widely used. A circuit analysis shows that the circulating power flow increases almost linearly as the phase difference increases, which adds extra load to the system and results in increased power dissipation and load unbalance. In this paper, we suggest a phase shifter for the parallel-feeding AC traction power system. The phase shifter regulates the phase difference and the circulating power flow by injecting quadrature voltage which can be obtained directly from the Scott-connection transformer in the traction substation. A case study involving the phase shifter applied to the traction power system of a Korean high-speed rail system shows that a three-level phase shifter can prevent circulating power flow while the phase difference between substations increases up to 12 degrees, mitigate the load unbalance, and reduce power dissipation.

• Analytical Science and Technology
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• v.7 no.3
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• pp.253-260
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• 1994

Analytical characteristics of low power-low flow inductively coupled plasma-atomic emission spectometry(ICP-AES) has been studied. Although the net intensity of the low power ICP is lower than the moderate power ICP, the signal to background ratio becomes higher since the background intensity decreases with decreasing the RF power. The detection limit of the low power ICP is comparable with that of the moderate power ICP. The dynamic range of the calibration curve of the low power ICP is $10^4{\sim}10^5$. The ionization interferences by alkali metals increase with increasing the carrier gas flow rate, but the effects are not varied significantly with the RF power.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.101-105
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• 1999

The goal of this paper is to present instantaneous compensating power flow of active power filters(APFs) by graphical method that could be practicable to compensate the power in both case of behaving in instantaneous rectifying mode and instantaneous inverting mode. To ensure the validity of the proposed method, computer simulation is achieved. Proposed method can be present more exquisite and physically meaningful power flow than conventional method in instantaneous compensating power flow Graph of APFs.

• Journal of international Conference on Electrical Machines and Systems
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• v.2 no.2
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• pp.246-253
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• 2013

The Modular Multilevel Converter (MMC) with full bridge cells is available for utility interactive inverter in high voltage line. When it is interconnected with power line, it is possible to control the active power flow in order to supply or charge the power in the line. This research applied the MMC to grid connection system of distributed generator and a power flow control for the MMC is investigated. Theory of power flow between the MMC and the power line is described and control method of power flow and capacitor voltages on arm cells for the MMC are proposed. And effectiveness of the proposed control method is presented by simulation.

• International Journal of Fluid Machinery and Systems
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• v.3 no.1
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• pp.58-66
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• 2010

A steam control valve is used to control the flow from the steam generator to the steam turbine in thermal and nuclear power plants. During startup and shutdown of the plant, the steam control valve is operated under a partial flow conditions. In such conditions, the valve opening is small and the pressure deference across the valve is large. As a result, the flow downstream of the valve is composed of separated unsteady transonic jets. Such flow patterns often cause undesirable large unsteady fluid force on the valve head and downstream pipe system. In the present study, various flow patterns are investigated in order to understand the characteristics of the unsteady flow around the valve. Experiments are carried out with simplified two-dimensional valve models. Two-dimensional unsteady flow simulations are conducted in order to understand the experimental results in detail. Scale effects on the flow characteristics are also examined. Results show three types of oscillating flow pattern and three types of static flow patterns.