• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.7
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• pp.824-832
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• 2018

According to the government's policy to demonstrate and expand the renewable energy sources, distributed generators such as PV and WP are installed and operated in distribution systems. However, there are many issues related to power quality problems including over voltage and under voltage of customers. In order to overcome these problems, the electric power company have installed a step voltage regulator (SVR) in primary feeders interconnected with distributed generators, and also have established the technical guidelines for the distributed generators to stabilize the customer voltages in distribution systems. However, it is difficult to maintain the customer voltages within allowable limit. Therefore, this paper reviews the problems of voltage control by SVR in a distribution systems interconnected with a large amount of PV systems, and proposes characteristics of operating range and voltage control limit of the small hydropower generators. Also, with the estimation of the influence to the power system voltages from the voltage control mode of generators, this paper proposes the optimal voltage control algorithm of the small hydropower generators. By programming the proposed algorithm into control simulator of exciter, it is confirmed that the proposed algorithm can contribute the voltage stabilization in distribution systems interconnected with large scaled PV systems.

• Journal of Environmental Science International
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• v.19 no.9
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• pp.1153-1159
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• 2010

Identification of probability distribution for water quality constituents from specific land use is important to achieve successful implementation of TMDL program. In this 3-year study, distribution of discharge and BOD(Biological Oxygen Demand) concentration from paddy rice fields were monitored. Four probability distributions, normal, log-normal, Gamma and Weibull were fitted and the goodness-of-fit was assessed using probability plots and Kolmogorov-Smirnov test. $EMC_s$ of BOD in runoff from paddy field ranged 0.37 to $7.99\;mgL^{-1}$, and all four probability distributions were acceptable. But the normal distribution would be preferred for BOD from paddy fields considering nature of straight forward application.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.838-846
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• 2015

This paper deals with the modified modeling of PV system based on the PSCAD/EMTDC and optimal control method of customer voltages in real distribution system interconnected with the photovoltaic (PV) systems. In order to analyze voltage variation characteristics, the specific modeling of PV system which contains the theory of d-q transformation, current-control algorithm and sinusoidal PWM method is being required. However, the conventional modeling of PV system can only perform the modeling of small-scale active power of less than 60 [kW]. Therefore, this paper presents a modified modeling that can perform the large-scale active power of more than 1 [MW]. And also, this paper proposes the optimal operation method of step voltage regulator (SVR) in order to solve the voltage variation problem when the PV systems are interconnected with the distribution feeders. From the simulation results, it is confirmed that this paper is effective tool for voltage analysis in distribution system with PV systems.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.5 no.6
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• pp.533-538
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• 2004

Recently, it is increasing the concern of distributed generations(DGs) that installed small power at a site near by the customer. In deregulation environment, not only distributed generation operation but also state estimation is the key function in distribution systems. This paper process to calculate the impact of distributed generation on a distribution feeder. WLAV state estimation is performed the distribution systems with DGs and bad data test including single, multiple, interacting. Simulations with test cases are performed and the results are presented, using IEEE 34 bus radial distribution systems

• Journal of the Semiconductor & Display Technology
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• v.13 no.3
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• pp.39-43
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• 2014

The effect of electrode charging on the ion energy distribution (IED) was investigated in the dual-frequency capacitively coupled plasma source which was powered of 100 MHz RF at the top electrode and 400 kHz bias on the bottom electrode. The charging property was analyzed with the distortion of the measured current and voltage waveforms. The capacitance and the resistance of electrode sheath can change the property of ion and electron charging on the electrode so it is sensitive to the plasma density which is controlled by the main power. The ion energy distribution was estimated by equivalent circuit model, being compared with the measured distribution obtained from the ion energy analyzer. Results show that the low frequency bias power changes effectively the low energy population of ion in the energy distribution.

• 제어로봇시스템학회:학술대회논문집
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• 1991.10b
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• pp.1790-1795
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• 1991

The optimal load distribution for two cooperating robots is studied in this paper, and a new solution approach utilizing force ellipsoid is proposed. The load distribution problem is formulated as a nonlinear optimization problem with a quadratic cost function. The limit on instantaneous power is considered in the problem formulation as the joint torque constraints. The optimal solution minimizing energy consumption is obtained using the concept of force ellipsoid and the nonlinear optimization theory. The force ellipsoid provides a useful geometrical insight into the load distribution problem. Despite the presence of the joint torque constraints, the optimal solution is obtained almost as a closed form, in which the joint torques are given in terms of a single scalar parameter that can be obtained numerically by solving a scalar equation.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.1996-2000
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• 2008

In autothermal reforming reaction, oxygen to carbon ratio (OCR) and steam to carbon ratio (SCR) are significant factors, which control temperature and carbon deposition into the reactor. The OCR is more sensitive than the SCR to affect the temperature distribution and reforming efficiency. In conventional operation, hydrocarbon fuel, steam, and oxygen was homogeneously mixed and injected into the reactor in order to get hydrogen-rich gas. The temperature was abruptly raised due to fast oxidation reaction in the former part of the reactor. Deactivation of packed catalysts can be accelerated there. In the present study, therefore, the effect of the oxygen distribution is introduced and investigated to suppress the carbon deposition and to maintain the reactor in the mild operating temperature (e.g., $700{\sim}800^{\circ}C$). In order to investigate the effect numerically, the following models are adopted; heterogeneous reaction model and two-medium model for heat balance.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 1998.06a
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• pp.128-133
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• 1998

This paper aims to present some ideas for implementation of Uncertain Relational Databases (URD) which are extensions of classical relational databases. Our system firstly is based on possibility distribution and probability theory to represent and manipulate fuzzy and probabilistic information, secondly adopts flexible mechanisms that allow the management of uncertain data through the resources provided by both available relational database management systems and front-end interfaces, and lastly chooses dynamic SQL to enhance versatility and adjustability of systems.

• Proceedings of the KIEE Conference
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• 1995.11a
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• pp.67-70
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• 1995

Service restoration has become more important function in the distribution systems. Conventional scheme considers only the single criterion such as margin, switching number and thus lacks the practical power. This paper proposes a new scheme adopting tile fuzzy decision making technique, general ins a more effective restoration plan.

• Management & Information Systems Review
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• v.17
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• pp.67-81
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• 2005

Harbor function has been changed into physical distribution position harbor system for providing most suitable physical distribution service with comprehensive rationalization of international physical distribution over simple loading unloading, and change function by far. Thus, to change our country into advanced economy, the factor of growth obstacles was to be eliminated, or it is so important that the physical distribution base establishment enlarges to improve potential productivity. That is, self effort is needed for physical distribution competition system, adjustable arrangement of physical distribution area, the establishment of comprehensive informations system, physical distribution rationalization. Also, to enforce harbor productivity, harbor should be developed systemically to able to function of comprehensive harbor for enlargement of harbor establishment, the device of advanced harbor function height, the linkage between and city program, harbor operation or investment system provement, harbor technique or international cooperation advancement.