• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.443-444
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• 2014

Using the ESS(Energy Storage System) as a UPS(Uninterruptible Power Supply) is being studied recently. When the system is operating at UPS mode in integrated ESS and UPS system, the grid supplying power is disconnected and power from PV generation and battery are supplying to load. Operating in UPS mode, when PV generation power is diminished by partial or total clouded situation, DC-link voltage fluctuates. The fluctuation of DC-link voltage influences the load and system as sensitive loads may malfunction. This paper suggests the DC-link ripple voltage compensation algorithm in bi-directional converter. The algorithm stabilize the DC-link and load voltage.

• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.206-207
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• 2016

The intermittent characteristics of wind power (WP) may have negative effect on grid stability, especially in weak grid. WP fluctuation rate can be reduced by using energy storage system (ESS) through charging and discharging. The operation of ESS will decide its losses and lifetime of batteries. From this point, this paper proposes WP smoothing control by using short-term average of WP. In this case, the ESS will only operate at high WP fluctuation rate. Then, the output power of ESS will be estimated by short-term average value. The effectiveness of proposed method will be verified by comparing with conventional method. The simulation results will be carried out by using Matlab program.

• KEPCO Journal on Electric Power and Energy
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• v.8 no.2
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• pp.143-149
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• 2022

As ESS safety issues increase recently, there is a need to more precisely monitor the temperature of the ESS. In this paper, DTS technology for temperature monitoring of ESS batteries is introduced and the temperature measurement principle is explained. The temperature of the battery module is measured using the DTS system, and the thermal deviation between battery cells inside the battery module is analyzed. In order to analyze how thermal imbalance affects the charging and discharging performance of the battery, an accelerated degradation test was conducted. Cycle life characteristics analysis, battery surface temperature change, and AC impedance characteristics were conducted to analyze how the performance of battery cells differs according to temperature conditions.

• Journal of Ecology and Environment
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• v.48 no.2
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• pp.137-143
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• 2024

Background: The study was carried out to analyze the temporal changes of trade-offs (TOs) between two ecosystem services (ESs) before and after thinning in a Pinus koraiensis plantation on Mt. Gari from 2006 to 2021. As target variables, aboveground carbon (AGC) storage and species richness (SR) were chosen for regulating and supporting services. Thinning was applied from 2007 through 2008 with three treatments: 1) light thinning (LT), 2) heavy thinning (HT), and 3) control (Con). Results: Thinning influenced both AGC and SR. In 2021, AGC in the Con (111.1 t C ha^-1) was significantly higher compared to the LT (82.0 t C ha^-1) and HT (60.4 t C ha^-1) after thinning from 2007 to 2008. Also, SR was marginally higher in the LT (94 species) than in the Con (55 species) and HT (87 species) in 2011. Relative benefits of AGC and SR showed similar trends with the obtained values. In addition, the effects of thinning on TO varied among treatments and over time, demonstrating different degrees of TO between the two ESs. In the LT, TO was 0.13 in 2006 and slightly increased to 0.2 by 2021. TO in the HT exhibited a relatively rapid increase from 0.22 in 2006 to 0.58 by 2021, while To in the Con fluctuated, rising to 0.36 in 2011 from 0.1 in 2006 and decreasing to 0.25 by 2021. Among the three treatments, the degree of TOs between the two ESs was the lowest in the LT. Conclusions: Depending on thinning intensities, the responses of ESs and the degree of TOs vary. Regarding the balance between enhancements and TOs in ESs among treatments, the LT treatment showing intermediate carbon storage, higher SR, and lower TOs will be a proper silvicultural application.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.122-123
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• 2017

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.39-48
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• 2020

Since the fire accident of ESS (energy storage system) occurred at Gochang KEPCO Power Testing Center in August 2017, 29 fire cases with significant property losses have occurred in Korea. Although the cause of fire accidents have not been identified precisely, it should be considered battery and PCS (power conditioning system) as well as unbalance issues in the distribution system. In particular, circulating currents in a neutral line of a grid-connected transformer, which can affect a magnetized current, may have a negative effect on the ESS with unintentional core saturation and surge voltages at the secondary side of the transformer. Therefore, this paper proposes the modeling of the distribution system, which was composed of a substation, grid-connected transformer, and customer loads using PSCAD/EMTDC S/W, to analyze the phenomena of circulating current and surge voltages of the transformer with unbalanced currents in the distribution system. This paper presents a countermeasure for a circulating current with the installation of NGR (neutral grounding resistor) in grid-connected transformer. From the simulation results, it is clear that exceeding the circulating current and surge voltage at the secondary side of the transformer can be one of the causes of fire accidents.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.2
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• pp.187-192
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• 2019

Hybrid power storage system with emergency power function for demand management and power outage minimizes the investment cost in the building of buildings and factories requiring emergency power generation facilities, We propose a new business model by developing technology that can secure economical efficiency by reducing power cost at all times. Normally, system power is supplied to load through STS (Static Transfer Switch), and PCS is connected to system in parallel to perform demand management. In order to efficiently operate the electric power through demand forecasting, the EMS issues a charge / discharge command to the ESS as a PMS (Power Management System), and the PMS transmits the command to the PCS controller to operate the system. During the power outage, the STS is rapidly disengaged from the system, and the PCS becomes an independent power supply and can supply constant voltage / constant frequency power to the load side. Therefore, it is possible to secure reliability through verification of actual system linkage and independent operation performance of hybrid ESS, By enabling low-carbon green growth technology to operate in conjunction with an efficient grid, it is possible to improve irregular power quality and contribute to peak load by generating renewable energy through ESS linkage. In addition, the ESS is replacing the frequency follow-up reserve, which is currently under the charge of coal-fired power generation, and thus it is anticipated that the operation cost of the LNG generator with high fuel cost can be reduced.

• Fire Science and Engineering
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• v.34 no.2
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• pp.147-155
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• 2020

This paper presents a study on the development of a fire extinguishing agent and extinguishing system for an energy storage system (ESS) fire. The fire extinguishing agent designed to extinguish an ESS fire is a highly permeable fire extinguisher that reduces the surface tension and viscosity while bringing about cooling action. This is the main extinguishing effect of this type of wetting agent, which displays the characteristics of fire extinguishing agents used for penetrating the battery cells inside the ESS module. For the fire extinguishing system, a local application system was designed to suppress fire on a rack-by-rack basis. A 360° rotating nozzle was inserted into the rear hall of the ESS module, and general nozzles were installed in the rack to maximize the fire extinguishing effect. The fire extinguishing agent was strongly discharged by virtue of the gas release pressure. Experiments on fire suppression performance with ESS module 1 unit and module 3 units showed that all visible flames were extinguished in 8 s and 9 s, respectively, by the fire extinguishing agent. In addition, based on confirming reignition for 600 s after the fire extinguishing agent was exhausted, it was confirmed that the ESS fire was completely extinguished without reignition in all fire suppression performance experiments.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.67 no.3
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• pp.168-174
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• 2018

The performance test for 376MW ESS for frequency regulation currently operating in 13 substations is conducted based on the test procedure in the first and second steps. In the first step, components of ESS is moved to the certification authority where the test equipment is located in order to be proceeded with the test. In the second step, the performance test is conducted manually for the ESS equipments installed on site using the movable measurement equipment, and thus it can only be performed on some limited test items and requires a lot of time and manpower. Therefore, mobile test equipment for ESS(MOTES) is being developed that can perform automatically more test items for ESS in the field using the MOTES, and reduce manpower and time. To do this, an algorithm and a prototype of the operating system(MOS) are also being developed that can control MOTES automatically. In this paper, a development of the MOS prototype is introduced and then a simulation is performed to verify the prototype and its algorithm before the field demonstration.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.3
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• pp.377-382
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• 2016

In 2013, a total capacity of 591.3 MW of installed wind power generation was achieved in Korea, with a total of 1,139 MWh of wind energy generated that year. More wind power plants will be installed in the coming years, and it is important to develop methods to reduce the output variability of these resources so as to provide stable power to the power grid of Korea. In this regard, this paper proposes the use of energy storage system (ESS) as a means to stabilize the output variability of wind power plants. Presented in this paper is a method that uses Discrete Fourier Transform (DFT) to determine the ESS capacity needed to provide a stable power output for ancillary services such as frequency regulation, economic dispatch, and emergency reserves. In the first step of the proposed method, four regions (namely, Samdal, Yeongdeok, Yeongyang, and Gangwon) in Korea that had the most wind power generation capacity were selected for analysis. In the second step, the individual and aggregated wind power outputs of the selected regions in 2013 were obtained This information was then used in the third step, where DFT analysis of the power outputs was used to drive the magnitudes of the output variation. And finally, the ESS capacity requirements needed to provide different ancillary services were determined based on the magnitudes of the output variation.