• Journal of Power Electronics
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• v.12 no.5
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• pp.787-799
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• 2012

Real and reactive power flows on a transmission line interact inherently. This situation degrades power flow controller performance when independent real and reactive power flow regulation is required. In this study, a quasi multi-pulse interline power flow controller (IPFC), consisting of eight six-pulse voltage source converters (VSC) switched at the fundamental frequency is proposed to control real and reactive power flows dynamically on a transmission line in response to a sequence of set-point changes formed by unit-step reference values. It is shown that the proposed hybrid fuzzy-PI commanded IPFC shows better decoupling performance than the parameter optimized PI controllers with analytically calculated feed-forward gains for decoupling. Comparative simulation studies are carried out on a 4-machine 4-bus test power system through a number of case studies. While only the fuzzy inference of the proposed control scheme has been modeled in MATLAB, the power system, converter power circuit, control and calculation blocks have been simulated in PSCAD/EMTDC by interfacing these two packages on-line.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.2
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• pp.331-337
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• 2015

The power flow analysis of electrified railway is required complicated calculation, because of variable load. Train runs trough rail supplied by electric power therefore, the load value in electrified railway system fluctuates along time. The power flow algorithm in electrified railway system is different from general power system, and the power flow simulation is peformed by the particular simulation software. Powerail is simulation software for analysis of traction power supply system developed by KRRI, in 2008. This consists of load forecasting module, including TPS and time scheduling, and power flow module. This software was verified by measured current under normal feeding condition, however, has not been verified by voltage on the condition of extended feeding. This paper presents the verification of PowerRail based on voltage drop under extended feeding condition. This is performed by comparing simulation result with field test. Field test and simulation is done in commercial railway line.

• Nuclear Engineering and Technology
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• v.52 no.4
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• pp.708-720
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• 2020

Core-wide temperature distribution in sodium-cooled fast reactor plays a key role in its decay heat removal process, however the prediction for temperature distribution is quite complex due to the conjugate heat transfer between the assembly flow and the inter-wrapper flow. Hybrid medium model has been proposed for conjugate heat transfer modeling in the core. The core is modeled with a Realistic modeled inter-wrapper flow and hybrid medium modeled assembly flow. To validate present model, simulations for a three-assembly model were performed with Realistic modeling, traditional porous medium model and hybrid medium model, respectively. The influences of Uniform/Non-Uniform power distribution among assemblies and the Peclet number within the assembly flow have been considered. Compared to traditional porous medium model, present model shows a better agreement with in Realistic modeling prediction of the temperature distribution and the radial heat transfer between the inter-wrapper flow and the assembly flow.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.20 no.6
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• pp.416-426
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• 2008

The boiler tube failure often experienced in the superheater of a utility boiler can seriously affect the economic and safe operation of the power plant. It has been known that this failure is mainly caused by the thermal load deviation in the superheater tube system, and deeply intensified by the non-uniform distribution of steam flow rates. The nonuniform steam flow is distinctively prominent at low power load rather than at full power load. In this paper, we analyze the steam flow distribution in the superheater tube system by using one dimensional flow network model. At 30% power load, the deviation of steam flow rate is predicted to be within 0.8% of the averaged flow rate. This deviation can be reduced to 0.1% and 0.07% by assuming two cases, that is, the removal of 13th tube at each tube rows and the installation of intermediate header, respectively. The assumed two cases would be effective for the uniform steam flow distribution across 85 superheater tube rows.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1290-1292
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• 1999

In this paper. continuation power flow for Power system including UPFC has been performed. The decoupled model, by which power flow can be performed without any modification of conventional power flow program is used as steady-state model. A numerical example has been given to analyze the influence on the voltage stability by UPFC.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.479-481
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• 1996

This paper describes a simulation model to analyze the dynamic performance of Unified Power Flow Controller which ran flexibly adjust the active and reactive power flow through the ac transmission line. An equivalent circuit to analyze the basic principle for the whole system operation was developed and a control system for the Unified Power Flow Controller was derived using vector control method. A computer simulation model with EMTP code was also conceived to evaluate the performance of the Unified power Flow Controller. The simulation results show that Unified Power flow Controller is very effective for controlling the power flow and damping the subsynchronous resonance in the power system.

• Proceedings of the KIEE Conference
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• 1999.07c
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• pp.1158-1160
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• 1999

This paper proposes a SSSC(Static Synchronous Series Compensator) power flow model to be incorporated into power flow calculation for the steady state analysis of the power system. SSSC provides controllable compensating voltage, which is in quadrature with the line current, over an capacitive and an inductive range, independently of the magnitude of the line current. This SSSC model is obtained from the injection model for series connected VSC(Voltage Source Converter) by adding a constraint that the injected voltage should be in quadrature with the line current. In this paper the static model is implemented into the continuation power-flow (CPF) program. It is shown that SSSC has its intrinsic superiority over TCSC in controllable power flow range.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.15 no.2
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• pp.21-30
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• 2001

In this paper, in the power system having UPFC(Unified Power Flow Controller) Power flow of certain line is controlled to desired value also power flow analysis algorithm is reposed considering power flow constraints which is capable of analysis power flow of all system. This algorithm is applied to controlling line-overloading problems and the method of is prosed. By applying this algorithm to controlling line-over loading the method of controlling UPFC is proposed and the effectiveness of controlling UPFC is proposed and the effectiveness of controlling UPFC is verified through the research of practical system. Also, the equation to set up an initial value of stories and shunt voltage source of UPFC is proposed for the effective power analysis.

• Journal of Electrical Engineering and Technology
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• v.12 no.4
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• pp.1586-1592
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• 2017

Voltage sourced converter (VSC) based direct-current (DC) grid has the ability to control power flow flexibly and securely, thus it has become one of the most valid approaches in aspect of large-scale renewable power generation, oceanic island power supply and new urban grid construction. To solve the optimal power flow (OPF) problem in DC grid, an adaptive particle swarm optimization (PSO) algorithm based on fuzzy control theory is proposed in this paper, and the optimal operation considering both power loss and voltage quality is realized. Firstly, the fuzzy membership curve is used to transform two objectives into one, the fitness value of latest step is introduced as input of fuzzy controller to adjust the controlling parameters of PSO dynamically. The proposed strategy was applied in solving the power flow issue in six terminals DC grid model, and corresponding results are presented to verify the effectiveness and feasibility of proposed algorithm.

• KIEE International Transactions on Power Engineering
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• v.5A no.4
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• pp.390-395
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• 2005

The most widely used index for the vulnerable area investigation has been the reactive power margin or sensitivity analysis. But we can only obtain the results of these analyses if the results of load flow are convergent in severe contingencies. Otherwise these methods are not adoptable. This paper presents a good index for overcoming severe contingencies, though the power flow equation is unsolvable using the branch parameter continuation power flow. In simulation, the Korea Electric Power Corporation (KEPCO) Systems are applied.