• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3391-3398
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• 2015

Recently, the large scaled lead-acid battery is widely introduced to efficient operation of the photovoltaic system in many islands. but the demand of lithium-ion battery is getting increased by the operation of wind power and replacement of the lead-acid battery. And also, under the renewable portfolio standard(RPS) and energy efficiency resource standard(EERS) policy of Korea government, the introduction of energy storage system(ESS) has been actively increased. Therefore, this paper presents the operation algorithm of hybrid battery management system(BMS) using the lead-acid and lithium-ion batteries, in order to maximize advantage of each battery. In other words, this paper proposed the algorithm of state of charge(SOC) and hybrid operation algorithm to calculate the optimal composition rate considering the fixed cost and operation cost of each battery. From the simulation results, it is confirmed that the proposed algorithms are an effective tool to evaluate SOC and to optimally operate hybrid ESS.

• Journal of Drive and Control
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• v.7 no.2
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• pp.33-41
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• 2010

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.2
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• pp.317-324
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• 2007

Most conventional hybrid systems using renewable energy sources have been applied for stand-alone operation, but Utility-interface may be an useful and viable option for hybrid systems. Grid-connected operation may have benefits such as reduced losses in power system distribution, utility support in demand side management, and peak load shaving. This paper addresses power control and dynamic performance of a grid-connected PV/wind/BESS hybrid system. At all times the PV way and the wind turbine are individually controlled to generate the maximum energy from given weather conditions. The battery energy storage system (BESS) charges or discharges the battery depending on energy gap between grid invertger generation and production from the PV and wind system. The BESS should be also controlled without too frequently repeated shifts in operation mode, charging or discharging. The grid inverter regulates the generated power injection into the grid. Different control schemes of the grid inverter are presented for different operation modes, which include normal operation, power dispatching, and power smoothing. Simulation results demonstrate that the effectiveness of the proposed power control schemes for the grid-interactive hybrid system.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.9
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• pp.100-108
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• 2003

This paper proposes a flywheel hybrid vehicle to solve the energy crisis problem by the exhaustion of a fossil fuel and air pollution for the conservation of environment. The proposed flywheel hybrid vehicle is composed of an accumulator and a flywheel as the energy generation and storage component and three variable displacement hydraulic pump/motors as the energy transfer devices. Flywheel has the characteristics of high energy density and easy energy absorption and consumption. The effectiveness of the energy-saving of the proposed flywheel hybrid vehicle is verified by simulation using Matlab/simulink. First of ail, analytical modeling for the flywheel hybrid vehicle is presented and simulations are performed based on the experimental efficiency data of a variable displacement pump/motor. The results of the simulation show that the effect of energy savings is realized by the proposed hybrid vehicle in 3 different city driving patterns.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.1
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• pp.11-18
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• 2015

This paper proposes a high-efficiency 3-kW hybrid ESS with emergency power supply. The proposed system enables efficient use of power from photovoltaic (PV) cells and energy storage system (ESS). The proposed system can operate as an uninterruptible power supply (UPS) when grid fault occurs, providing seamless transfer from grid-connected mode to stand-alone mode. The LLC converter for PV achieves ZVS turn-on of switches and ZCS turn-off of diodes, and the isolated bidirectional DC-DC converter for ESS achieves ZCS turn-off regardless of load condition, resulting in high efficiency. The efficiency and performance of the proposed hybrid ESS has been verified by a 3-kW prototype.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.3
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• pp.16-23
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• 2012

This paper relates to a study on the economic of electrical storage device for supplying power in sunless days, in the stand alone PV/Wind hybrid system, which it is applied to separate houses. In a photovoltaic/wind hybrid power system used in a separate house, when only the battery is used in sunless days, the capacity of the battery is become larger. For example, as in recent days, if cloudy days are frequent due to anomaly climate, it is difficult to supply power stably by only the battery based upon pre-estimated sunless days. Accordingly, in order to supply stably power of new renewable energy such as solar to any separate houses, it is preferable to reduce the capacity of battery by decreasing the number of sunless days when estimating the capacity of battery and to drive the small generator for compensation of the power shortage.

• The Journal of Society for e-Business Studies
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• v.15 no.4
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• pp.101-121
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• 2010

This paper presents an intelligent prefetching technique that significantly improves performance of hybrid fash-disk storage, a combination of flash memory and hard disk. Since flash memory embedded in a hybrid device is much faster than hard disk in terms of I/O operations, it can be utilized as a 'cache' space to improve system performance. The basic strategy for prefetching is to utilize sequential pattern mining, with which we can extract the access patterns of objects from historical access sequences. We use two techniques for enhancing the performance of hybrid storage with prefetching. One of them is to modify a FAST algorithm for mapping the flash memory. The other is to extend the unit of prefetching to a block level as well as a file level for effectively utilizing flash memory space. For evaluating the proposed technique, we perform the experiments using the synthetic data and real UCC data, and prove the usability of our technique.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.11
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• pp.57-68
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• 2013

The market for distributed power generation based on renewable energy is increasing, particularly for standalone mini-grid applications in developing countries with limited energy resources. Stand-alone power systems (SAPS) are of special interest combined with renewable energy design in areas not connected to the electric grid. Traditionally, such systems have been powered by diesel engine generator sets (DEGS), but also hybrid systems with photovoltaic and/or wind energy conversion systems (WECS) are becoming quite common nowadays. Hybrid energy systems can now be used to generate energy consumed in remote areas and stand-alone microgrids. This paper describes the design, simulation and feasibility study of a hybrid energy system for a stand-alone power system. A simulated model is developed to investigate the design and performance of stand-alone hydrogen renewable energy systems. The analysis presented here is based on transient system simulation program (TRNSYS) with realistic ventilation load of a large store. Design of a hybrid energy system is site specific and depends on the resources available and the load demand.

• Journal of IKEEE
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• v.17 no.3
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• pp.301-308
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• 2013

In this paper, we propose the hybrid lighting control system on multiple sensor. The proposed hybrid lighting control system was designed for management and control of street lightings by configured as the data display part of integration-interworking part, the data conversion-processing part of integrated management part, and the communication part of gateway system. The data are implemented to designing the DB to enable to storage in real-time by enable to monitoring by wireless remote control and schedule set. As a result of the efficiency verification of the proposed hybrid lighting control system, the hybrid lighting control system be to the real-time monitoring and remote lighting control was possible, because to peristalsis with smart devices and portable PC etc., and it could be obtained the effect of energy and electricity, communication cost reduction.

• Applied Chemistry for Engineering
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• v.23 no.4
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• pp.359-366
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• 2012

Zn-Air energy storage cell is an attractive type of batteries due to its theoretical gravimetric energy density, cost-effective structure and environmental-friendly characteristics. The chargeability is the most critical in various industrial applications such as smart portable device, electric vehicle, and power storage system. Thus, it is necessary to reduce large overpotential of oxygen reduction/evolution reaction, the irreversibility of Zn anode, and carbonation in alkaline electrolyte. In this review, we try to introduce recent studies and developments of bi-functional air cathode, enhanced charge efficiency via modification of Zn anode structure, and blocking side reactions applying hybrid organic-aqueous electrolyte for high power density rechargeable Zn-Air energy storage cells.