• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.8
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• pp.1168-1179
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• 2015

This paper presents voltage and frequency control methods for a stand-alone Gasa Island Microgrid in South Korea that can be fully energized by renewable energy resources such as photovoltaic systems and wind turbines. To mitigate the variations of the output of renewable energy resources and supply more reliable electricity to customers, battery energy storage systems (BESSs) are employed in the stand-alone microgrid. The coordination between BESSs and pre-existing diesel generators is an important issue to manage the microgrid more securely. This paper presents voltage and frequency control schemes considering the coordination of BESSs and DGs. The effectiveness for the operating method is validated via simulation studies.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.122-123
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• 2013

본 논문에서는 배터리를 포함한 태양광 발전 시스템에 직류배전 기능을 추가하여 효율적인 전력운용이 가능한 UPCS (Universal Power Conditioning System)의 구성 및 운용 알고리즘을 제안한다. 제안된 알고리즘과 토폴로지는 시뮬레이션을 통하여 기능을 검증하고 실제 가정용을 대상으로 3kW의 시제품을 제작하여 성능을 검증한다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.7
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• pp.1295-1302
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• 2016

In this paper, a black box, which is provided the reliability and user safety of home battery energy storage system connected with solar energy generation, is developed. In the developed scheme, a status and diagnosis data of battery management system, power conditioning system, solar energy generation and grid is measured. This status and diagnosis data is stored and displayed in the developed black box. In addition, this status and diagnosis data is stored and displayed in a monitoring system and a smart phone of user. A performance evaluation of the developed black box is carried out using emulator of home battery energy storage system connected with solar energy generation. Consequently, the developed black box is proved its superiority of the reliability and user safety.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.7
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• pp.950-956
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• 2012

As development of battery technologies, the installation of Battery Energy Storage System (BESS) increased. The BESS can be used for various purposes such like frequency response, load leveling, and fluctuation mitigation of renewable energy generators. In this paper, three state BESS model is proposed. the BESS model considering charge, discharge and keeping efficiency, and life cycle according to depth of discharge (DOD). Then, the benefit and cost of BESS installed at substation for load leveling are summarized. The economic evaluation of BESS is analyzed using net present values (NPV) analysis. In case study, the NPV analysis of NaS battery system is carried out using the proposed BESS model. Because the result of economic evaluation of BESS using nowadays cost data is not positive, the sensitivity analysis of BESS is conducted by changing the capital cost and energy cost.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.2
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• pp.477-485
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• 2015

Most existing simulators for wireless sensor networks(WSNs) are modeling battery-based sensors and providing MAC and routing protocols designed for battery-based WSNs. However, recently, as energy harvesting sensor systems have been studied more extensively, there is an increasing need for appropriate simulators, but few related studies have employed such simulators. Unlike existing simulators, simulators for energy harvesting WSNs require a new energy model that is integrated with the energy-harvesting model, rechargeable battery model, and energy-consuming model. Additionally, it should enable the applications of the well-known MAC and routing protocols designed for energy-harvesting WSNs, as well as a user-friendly interface for convenience. In this work, we design and implement a user-friendly simulator for solar energy-harvesting WSNs.

• Journal of IKEEE
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• v.25 no.3
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• pp.462-466
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• 2021

DVR is a device that compensates for voltage fluctuations in distribution lines and is generally used in combination with a device that compensates reactive power and improve power factor. Such a coupling compensator has the disadvantage of being relatively difficult to control and bulky. In this paper, mathematical analysis of the maximum magnitude of the compensation voltage, phase angle, compensable reactive power and active power was performed in order to simultaneously compensate the reactive power and voltage fluctuation of the distribution line by applying the power angle control method of the DVR. A control algorithm for charging active power to the battery and supplying stored energy when the voltage is changed was developed and the results were confirmed through Matlab simulation.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.6
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• pp.587-593
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• 2011

A new high power density and low cost Photovoltaic Power Conditioning System (PV PCS) with energy storage system is proposed. Its high power density and cost effectiveness can be achieved through the unification of the maximum power point tracker and battery charger/discharger. Despite of the reduced power stage, the proposed system can achieve the same performances of maximum power point tracking and battery charging/discharging as the conventional system. Moreover, the high voltage stress across the link-capacitor can be relieved through the series-connected link-capacitor with the battery. Therefore, a large number of series/parallel-connected link-capacitors can be reduced by 4-times. Especially, when the utility power failure happens, both photovoltaic and battery energies can be supplied to the load with only one power stage. Therefore, it features a simpler structure, less mass, lower cost, and fewer devices. Finally, to confirm the operation, validity, and features of the proposed system, theoretical analysis and experimental results from a single phase AC 220Vrms/1.5kW prototype are presented.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.6
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• pp.662-671
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• 2020

Recently, for the purposes of reducing carbon dioxide(CO₂) emissions in the island area, countermeasures to decrease the operation rate of diesel generator(DG) and to increase one of renewable energy sources(RES) is being studied. In particular, the demonstration and installation of stand-alone micro-grid(MG) system which is composed of DG, RES and energy storage system(ESS) has been implemented in some island areas such as Gapa-do, Gasa-do and Ulleung-do island. However, many power quality(PQ) problems may be occurred due to an intermittent output of RES including photovoltaic(PV) system and wind power(WP) system in a normal operating of constant voltage & constant frequency(CVCF) inverter-based MG system. Therefore, this paper presents a modeling of the 30kW scale MG system using PSCAD/EMTDC, and also implements a 30kW scale CVCF inverter-based MG system as test devices to analyze normal operating characteristics of MG system. From the simulation and test results, it is confirmed that the proposed methods are useful and practical tools to improve PQ problems such as under-voltage, over-voltage and unbalanced load in CVCF inverter-based MG system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.4
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• pp.568-574
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• 2020

Recently, the installation of energy storage systems (ESSs) that have a range of functions, such as power stabilization of renewable energy sources, demand control, and frequency regulation, has been increasing annually. On the other hand, since the fire accident of ESS occurred at Gochang Power Test Center in August 2017, 29 fire accidents with significant property losses have occurred, including the Gyeongsan substation and Kunsan PV power plant. Because these fire accidents of ESS are arisen regardless of the season and capacity of ESS, an analysis of the fault characteristics in ESS is required to confirm the causes of the fire accidents accurately and ensure the safety of the ESS. This paper proposes the modeling of ESS using PSCAD/EMTDC S/W to identify the fault characteristics and ensure the safety of the ESS. From the simulation results of fault characteristics based on various scenarios, it is clear that the insulation of ESS may be breakdown due to the largely occurring CMV (common mode voltage). Furthermore, the CMV between the PCS and battery can be reduced, and the insulation breakdown of ESS can be prevented if an SPD (surge protect device) is installed in the battery and PCS sides, respectively.

• Korean Chemical Engineering Research
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• v.55 no.3
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• pp.332-340
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• 2017

This study aims to propose a new optimization-based approach for design and analysis of the stand-alone hybrid energy supply system using renewable energy sources (RES). In the energy supply system, we include multiple energy production technologies such as Photovoltaics (PV), Wind turbine, and fossil-fuel-based AC generator along with different types of energy storage and conversion technologies such as battery and inverter. We then select six different regions of Korea to represent various characteristics of different RES potentials and demand profiles. We finally designed and analyzed the optimal RES stand-alone energy supply system in the selected regions using multiobjective optimization (MOOP) technique, which includes two objective functions: the minimum cost and the minimum $CO_2$ emission. In addition, we discussed the feasibility and expecting benefits of the systems by comparing to conventional systems of Korea. As a result, the region of the highest RES potential showed the possibility to remarkably reduce $CO_2$ emissions compared to the conventional system. Besides, the levelized cost of electricity (LCOE) of the RES-based energy system is identified to be slightly higher than conventional energy system: 0.35 and 0.46 $/kWh, respectively. However, the total life-cycle emission of $CO_2$ ($LCE_{CO2}$) can be reduced up to 470 g$CO_2$/kWh from 490 g$CO_2$/kWh of the conventional systems.