• New & Renewable Energy
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• v.10 no.3
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• pp.47-54
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• 2014

Recently, BESS is considered as one of essential countermeasure for demand side management. However, an economic evaluation is critical issue for the introduction of power system because the cost of BESS is very high in present stage. Therefor, this paper presents economic evaluation method for customer use case by considering peak shaving function based on the real time price. From the case study on the model power system and educational customer, it is confirmed that the proposed method is a practical tool for the economic analysis of BESS. and analytical approach for the reliability assessment in radially operated distribution systems. The approach can estimate the expected reliability performance of distribution systems by a direct assessment of the configuration of the systems using the reliability indexes such as NDP (Non-Delivery Power) and NDE (Non-Delivery Energy). The indexes can only consider the number and configuration of the load, but can not consider the characteristics of the load which is the one of the most important factor in the investment cost for the distribution systems. Therefore, this paper presents the new performance indexes for the investment of the distribution facilities considering both the expected interruption cost for the load section and the operation characteristics of Energy Storage System. The results from a case study show that the proposed methods can be a practical tool for the reliability management in distribution systems including Energy Storage System.

• Journal of Hydrogen and New Energy
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• v.35 no.4
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• pp.370-376
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• 2024

Load variations reduce the lifespan of polymer electrolyte fuel cells (PEFCs). To analyze the impact of load variations on durability of PEFCs, two stacks were built and operated continuously for 400 hours, one under load variations and the other under constant current condition with the same energy output. Using the example model provided by Mathworks, we obtained load variation data for the experiments. The performance curves were measured every 100 hours and analyzed by current interruption method and electrochemical impedance spectroscopy. The degradation comparison shows a much larger decrease in performance under the load variation. The activation resistance, electrical resistance, and mass transfer resistance are all found to increase more.

• Proceedings of the KIEE Conference
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• 2001.11b
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• pp.286-288
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• 2001

This paper deals with the analytical approach for the reliability assessment in radially operated distribution systems. The existing indexes can consider the number and configuration of the load, but can not consider the characteristics of the load which is the one of the most important factor in the investment cost for the distribution systems. Therefore, This paper presents the new indexes considering the expected interruption cost for the load section and protection systems in the cafe where the Dispersed Storage and Generation Systems are introduced to distribution systems. And this paper shows the effectiveness of the proposed methods by simulating at the model systems.

• Smart Structures and Systems
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• v.2 no.3
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• pp.275-293
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• 2006

For health monitoring purpose usually the structure is instrumented with a large scale and multichannel measurement system. In case of highway bridges, operating vehicle could be utilized to reduce the number of measuring devices. First this paper presents a static damage detection algorithm of using operating vehicle load. The technique has been validated by finite element simulation and simple laboratory test. Next the paper presents an approach of using this technique to field application. Here operating vehicle load data has been used by instrumenting the bridge at single location. This approach gives an upper hand to other sophisticated global damage detection methods since it has the potential of reducing the measuring points and devices. It also avoids the application of artificial loading and interruption of any traffic flow.

• ETRI Journal
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• v.36 no.5
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• pp.761-771
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• 2014

Long-Term Evolution employs a hard handover procedure. To reduce the interruption of data flow, downlink data is forwarded from the serving eNodeB (eNB) to the target eNB during handover. In cellular networks, unbalanced loads may lead to congestion in both the radio network and the backhaul network, resulting in bad end-to-end performance as well as causing unfairness among the users sharing the bottleneck link. This work focuses on congestion in the transport network. Handovers toward less loaded cells can help redistribute the load of the bottleneck link; such a mechanism is known as load balancing. The results show that the introduction of such a handover mechanism into the simulation environment positively influences the system performance. This is because terminals spend more time in the cell; hence, a better reception is offered. The utilization of load balancing can be used to further improve the performance of cellular systems that are experiencing congestion on a bottleneck link due to an uneven load.

• Journal of Electrical Engineering and Technology
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• v.11 no.3
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• pp.675-682
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• 2016

Sudden voltage drops and outages frequently disturb the operation of sensitive loads for domestic, commercial, and industrial use. In some cases, these events may even impair the functioning of relevant equipment. To maintain power under such conditions, a UPS system is usually installed. Once a disturbance happens at the grid side, the line-interactive UPS system takes over the load to prevent an interruption. But, due to magnetic saturation of the transformer, a significant inrush current may occur for the transformer-coupled loads during this transition. The generation of such transient currents may in turn decrease the line voltage and activates over-current protecting devices of the system. In this work, a cost-effective, line-interactive UPS system is proposed that eliminates the inrush current phenomenon associated with transformer-coupled loads. The strategy was implemented by connecting a standard current-regulated voltage source inverter (CRVSI) to the secondary winding of the load transformer. During any transient condition at the grid side, the load current is monitored and regulated to achieve either seamless compensation of the load current or complete transferal of load from grid to the inverter. Experimental results were obtained for a prototype under all possible operating conditions so as to validate the performance of the proposed topology.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.3
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• pp.513-521
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• 2017

Robust optimal operation of a microgrid is required since the increase of the penetration level of renewable generators in the microgrid raises uncertainty due to their intermittent power output. In this paper, an application of probabilistic optimization method to economical operation of a microgrid is studied. To simplify the treatment of the uncertainties of renewable generations and load, the new 'band of virtual equivalent load variation' is introduced considering their uncertainties. A simplified robust optimization methodology to generate the scenarios within the band of virtual equivalent load variation and to obtain the optimal solution for the worst scenario is presented based on Monte Carlo method. The microgrid to be studied here is composed of distributed generation system(DGs), battery systems and loads. The distributed generation systems include combined heat and power(CHP) and small generators such as diesel generators and the renewable energy generators such as photovoltaic(PV) systems and wind power systems. The modeling of the objective function for considering interruption cost by the penalty function is presented. Through the case study for a microgrid with uncertainties, the validity of proposed robust optimization methodology is evaluated.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.12
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• pp.133-140
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• 2013

Cascaded H-Bridge multi-level inverters can be implemented through the series connection of single-phase modular power bridges. In recent years, multi-level inverters are becoming increasingly popular for high power applications due to its improved harmonic profile and increased power ratings. This paper presents a control method for balancing the dc-link voltage and ride-through enhancement, a modified pulse width-modulation Compensation algorithm of cascaded H-bridge multi-level inverters. During an under-voltage protection mechanism, causing the system to shut down within a few milliseconds after a power interruption in the main input sources. When a power interruption occurs finish, if the system is a large inertia restarting the load a long time is required. This paper suggests modifications in the control algorithm in order to improve the sag ride-through performance of ac inverter. The new proposed strategy recommends maintaining the DC-link voltage constant at the nominal value during a sag period, experimental results are presented.

• Computers and Concrete
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• v.32 no.4
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• pp.411-423
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• 2023

The rapid development of road transport has increased the number of bridges that require widening. A critical issue in the construction of bridge widening is the influence of vibrations of the old bridge on the casting of wet joint concrete between the old and new bridges owing to the running traffic. Typically, the bridge is closed to traffic during the pouring of wet joint concrete, which negatively affects the existing transportation network. In this study, a newly developed microscopic traffic load modeling approach and the vehicle-bridge interaction theory are incorporated to develop a refined numerical framework for the analysis of random traffic-bridge coupled dynamics. This framework was used to investigate traffic-induced vibrations at the wet joint of a widened bridge. Based on an experimental study on the vibration resistance of wet joint concrete, traffic control strategies were proposed to ensure the construction performance of cast-in-site wet joint concrete under random traffic without interruption. The results show that the vibration displacement and frequency of the old bridge, estimated by the proposed framework, were comparable with those obtained from field measurements. Based on the target peak particle velocity and vibration amplitude of the wet joint concrete, it was found that traffic control measures, such as limiting vehicle gross weight and limiting traffic volume by closing an additional traffic lane, could ensure the construction performance of the wet joint concrete.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.427-430
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• 2003

Steel piling for abutments of new and replacement bridges can be aesthetically attractive and cost effective. Use of embedded steel sheet piling brings savings in dead load, provides a compliant retaining wall, and permits speedier construction. In addition, for replacement bridge projects, traffic interruption can be minimized. It is hoped that this study will encourage designers and constructors to consider a steel substructure option more frequently during the conceptual and preliminary design phases of projects and thereby to take advantage of the Potential to construction more efficiently.