• Proceedings of the KIEE Conference
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• summer
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• pp.1254-1256
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• 2004

This paper deals with a novel 3-phase power quality disturbance generator. The proposed generator can be applied to the performance that of custom power devices. Voltage sag, swell and outage are provided by the generator. The control scheme for the disturbance generation is simple, and hardware setup is cost effective, compared with conventional scheme. The operating principle of the generator is described and the usefulness verified through simulation with 10KVA power rating.

• Journal of Electrical Engineering and Technology
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• v.9 no.3
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• pp.796-802
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• 2014

South Korea is recently under serious situation in supplying electricity with enough power reserve. A single fault of power plant at a peak-load time may lead to a total blackout for whole area connected by a single electric grid and isolated from other grids. Despite of the seriousness of blackout, however, there are scarce studies with ex-ante analysis of the economic costs from blackout. In order to evocate the seriousness, we calculate the economic costs for both industrial and household sectors with using some survey data and statistical methodologies. As a result, total economic costs are 39.23 trillion KRW (35.83 trillion KRW for industrial sector, 3.40 trillion KRW for household sector).

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.5
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• pp.463-470
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• 2006

This paper deals with a new 3-phase power quality disturbance generator. The proposed generator can provide phase jump as well as voltage sag, swell, outage, unbalance, and over and under voltage. The operating principle of the generator is described in each mode of disturbance. The magnitude of the phase jump is analysed and it is found that the magnitude is the function of the turn-ratios of the transformers consisting the generator. The scheme has simple structure compared with the conventional one, and the major components of the proposed scheme are SCR thyristor and transformer, which guarantees high reliability and cost-effective implementation of the generator. Furthermore, high efficiency can be obtained because there is no PWM switching of the semiconductor devices, and it is easy to control the system. Simulations are carried out to confirm the operation in each disturbance mode, and experiments has been done with 5kVA power rating. The usefulness of the proposed scheme is verified through simulation and experimental results. It is expected that the scheme can be applied to the performance test of the custom power devices such as UPS, DVR, DSTATCOM, and SSTS with cost-effective system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.1A
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• pp.25-33
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• 2003

We derive the outage probabilities for the Erlang capacity and link margin based on handoffs in the reverse link of a CDMA system of 14.4 kbps/1.9 GHz band, calculate them with the same parameters, and then with the maximum realizable Erlang capacity analyze newly the cell coverage in different areas by the COST-231 model If it decreases from 5 % to 2 % in case of $E_b/N_0$=5 dB under a soft handoff, the result shows a very reliable link with additional increment of 0.88 dB in the margin and a high quality of service within the coverage decrease of 0.12 km, 0.25 km, and 1 km in a city, suburban, and open areas respectively on the decrease of 2 Erlang in the capacity. When the $E_b/N_0$ decreases from 7 dB to 5 dB within the outage probability of 5 %, it shows the increase of 9 Erlang and of 0.2 km in a city on the same margin of 2.8 dB. Then, comparing it with a single cell, it shows the decrease of more than 10 Erlang in the capacity, but the enlargement of 0.17 km, 0.3 km, and 1 km in them on the margin decrease of 1.31 dB, also, with a hard handoff, the soft handoff gain of the increase of 10 Erlang and of 0.22 km, 0.5 km, and 2 km on the decrease of 2.16 dB.

• ETRI Journal
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• v.40 no.3
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• pp.318-329
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• 2018

Femtocell (FC) technology envisaged as a cost-effective approach to attain better indoor coverage of mobile voice and data service. Deployment of FCs over macrocell forms a heterogeneous network. In urban areas, the key factor limits the successful deployment of FCs is inter-cell interference (ICI), which severely affects the performance of victim users. Autonomous FC transmission power setting is one straightforward way for coordinating ICI in the downlink. Application of intelligent control using soft computing techniques has not yet explored well for wireless networks. In this work, autonomous FC transmission power setting strategy using Adaptive Neuro Fuzzy Inference System is proposed. The main advantage of the proposed method is zero signaling overhead, reduced computational complexity and bare minimum delay in performing power setting of FC base station because only the periodic channel measurement reports fed back by the user equipment are needed. System level simulation results validate the effectiveness of the proposed method by providing much better throughput, even under high interference activation scenario and cell edge users can be prevented from going outage.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.1
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• pp.146-151
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• 2005

This paper describes a new voltage disturbance generator for the performance test of a 1-phase UPS(Uninterruptible Power Supply). The proposed scheme has the ability of voltage sag, swell, and outage generation. The structure of the proposed generator is simple and cost-effective. The voltage disturbance can be generated with easy control system. The circuit operation and characteristics of the proposed converter are described and the usefulness of the converter is verified through computer simulations and experimental results.

• Journal of Electrical Engineering and Technology
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• v.4 no.4
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• pp.467-475
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• 2009

Congestion management is one of the technical challenges in power system deregulation. This paper presents single objective and multi-objective optimization approaches for optimal choice, location and size of Static Var Compensators (SVC) and Thyristor Controlled Series Capacitors (TCSC) in deregulated power system to improve branch loading (minimize congestion), improve voltage stability and reduce line losses. Though FACTS controllers offer many advantages, their installation cost is very high. Hence Independent System Operator (ISO) has to locate them optimally to satisfy a desired objective. This paper presents optimal location of FACTS controllers considering branch loading (BL), voltage stability (VS) and loss minimization (LM) as objectives at once using GA. It is observed that the locations that are most favorable with respect to one objective are not suitable locations with respect to other two objectives. Later these competing objectives are optimized simultaneously considering two and three objectives at a time using multi-objective Strength Pareto Evolutionary Algorithms (SPEA). The developed algorithms are tested on IEEE 30 bus system. Various cases like i) uniform line loading ii) line outage iii) bilateral and multilateral transactions between source and sink nodes have been considered to create congestion in the system. The developed algorithms show effective locations for all the cases considered for both single and multiobjective optimization studies.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.41-45
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• 2007

Palo Verde Unit 1 nuclear power station which is located in Arizona, USA had been operating at reduced power levels around 25% since December 25, 2005 due to vibration in one of its shutdown cooling lines. During an outage from March 18, 2006 to July 7, 2006 the necessary work and modifications to remedy the situation were performed. It cost approximately $46million to buy electricity to replace that lost as a result of this event. Therefore in this study, the vibration of shutdown cooling lines in the same nuclear power plant in Korea as Palo Verde Unit 1 should be measured by the operating condition of power plant. And it was evaluated using the expression for allowable velocity in ASME OM-S/G-2003. From the result of this study it is evaluated whether it is safe or not. If not the countermeasure should be considered in this study.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.10
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• pp.52-58
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• 2009

In this paper, we propose a probability method to determine minimum capacity of energy storage system(ESS) for Micro-grid Because of high capital cost of ESS, It's very important to determine optimal capacity of ESS and for stable operation of Micro grid(MG), we should determine minimum capacity of ESS. The proposed method has abilities to consider forced outage rate of generators and intermittent of non-dispatchable generators and minimum capacity make MG keep energy balancing by oneself.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.3
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• pp.241-247
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• 2005

This paper deals with the operation of a flywheel energy storage UPS. The UPS has good features such as long life-time, improved efficiency, no environmental problems, reduced size and space, and low maintenance cost compared with the conventional UPS using battery. The operating principle of the UPS is analysed in each mode including voltage compensation as well as uninterruptible power supply. Especially, the tracking characteristic of the disturbed phase of the source voltage after outage is analysed. The usefulness of the system is proved through simulations and experiments.