• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.9
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• pp.769-776
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• 2015

In this paper, a broadband MIMO antenna using the metal cover that is one of the antenna radiators is designed and implemented on the PCB. The proposed antenna consists of a monopole and an IFA fed by the coupling structure and a metal cover radiator. Therefore, a monopole and an IFA with a metal cover radiator operate simultaneously through a hybrid form of operation. The antenna satisfies VSWR 3:1 at the bands of LTE class 13, class 14, CDMA, GSM900, DCS, PCS, WCDMA, LTE class 40 and WiFi. The maximum ECC of diagonally fed MIMO antenna is 0.186. The measured average gain and efficiency were -5.14~-1.28 dBi and 30.87~74.48 % over the desire bands, respectively.

• KEPCO Journal on Electric Power and Energy
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• v.5 no.3
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• pp.157-163
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• 2019

K-BEMS System was introduced to reduce peak load and to save total energy of the 120 buildings that KEPCO headquarter and branch offices use. K-BEMS system is composed of PV, battery, and hybrid PCS. In this system, ESS, PV, lighting is used to save building energy based on demand prediction. Currently, neural network technique for short past data is applied to demand prediction, and fixed scheduling method by operator for ESS charging/discharging is used. To enhance this system, KEPCO research institute has carried out this K-BEMS research project for 3 years since January 2016. As the result of this project, we developed new real-time highly reliable building demand prediction technique with error free and optimized automatic ESS charging/discharging technique. Through several field test, we can certify the developed algorithm performance successfully. So we will describe the details in this paper.

• Journal of KIISE
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• v.44 no.6
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• pp.573-580
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• 2017

Despite the recent remarkable advances in the computing power of mobile devices, the heat and battery problems still restrict their performances, particularly compared to PCs. Therefore, in the application of the ray-tracing technique for high-quality rendering, the consideration of a method that traces only the secondary rays while the effects of the primary rays are generated through rasterization-based OpenGL ES rendering is worthwhile. Given that most of the rendering time is for the secondary-ray processing in such a method, a new volume-grid technique for dynamic scenes that enhances the tracing performance of the secondary rays with a low coherence is proposed here. The proposed method attempts to model all of the possible spatial secondary rays in a fixed number of sampling rays, thereby alleviating the visitation problem regarding all of the cells along the ray in a uniform grid. Also, a hybrid rendering pipeline that speeds up the overall rendering performance by exploiting the mobile-device CPU and GPU is presented.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.4
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• pp.330-335
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• 2017

Increased fossil fuel consumption causes global warming, environmental pollution, and abnormal climate change. Wind-generated power installation is proposed to solve this problem. Recently, the wind power plant construction case encourages the installation of the energy storage system (ESS) to improve the intermittency of wind power. The maximized ESS operation profits connected to wind power are not generated in the simplest operation pattern of charging at night and discharging at day. The battery charging efficiency improvement should be considered to get more profits. Thus, there is a possibility of increasing ESS operation profits by analyzing the battery AC and DC charging/discharging efficiency and the yearly average sealed maintenance free (SMP) in hours. In this paper, the battery impedance characteristic, AC and DC charging/discharging efficiency, and the yearly average SMP are analyzed. The operation scenario to improve the ESS battery charging efficiency connected to wind power is proposed and verified via simulation.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.339-340
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• 2017

본 논문은 에너지 저장시스템(ESS)과 무정전 전원장치(UPS)를 하나로 통합한 새로운 하이브리드 ESS-UPS 시스템을 제안한다. 제안하는 시스템은 ESS와 UPS를 하나로 통합함으로써 전력변환 시스템(PCS)의 가격을 줄이고 배터리의 이용률을 높일 수 있다. 또한 기존의 on-line UPS와는 달리 두 종류의 중요부하를 구성할 수 있어 PCS의 용량대비 비상발전 용량을 증대시키는 것이 가능하다. 본 논문에서는 제안하는 하이브리드 ESS-UPS 시스템의 운영 전략 및 급속 모드전환 알고리즘을 제안하며, 5kW급 축소 시작품을 통한 실험 결과로 타당성을 입증하였다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.5
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• pp.82-91
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• 2014

The combined generator system by integrating several renewable energy sources can share the electrical infrastructure and therefore have the advantage of constructing not only the transmission system but also the power conversion system. Among the various combined renewable system, the wind power and wave power has a high possibility of future growth due to the economic feasibility in offshore environment. This kind of large-scale combined systems might be follow the determination by the transmission system operator's directions and control the output profile by focusing at PCC. However, both renewable energies are depend on the unpredictable environmental variation; it is needed to do the compensation devices. In this paper, the ESS compensation plan is proposed to do output determination of the combined generator system by paying attention to active power of utility grid with the analysis of the controllable elements of the wind and wave power generator. The improvement of the new application technique of the combined system is confirmed through using the PSCAD/EMTDC. The entire simulation process was designed by adopting the active power control according to the reference signal of TSO.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.159-160
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• 2015

최근 초기 투자비용은 큰 반면 에너지 이용률은 낮은 UPS(Uninterruptible power supply)를 ESS(Energy storage system)로서 활용하는 하이브리드 ESS에 대한 관심이 커지고 있다. 하이브리드ESS는 비상시 중요부하에 공급할 최소 전력을 제외한 전력을 수요관리로 활용함으로써 UPS에 저장되어 있는 에너지를 비상전원 기능과 수요관리 기능으로 폭넓게 사용할 수 있는 시스템이다. 이 시스템을 구성하는 3개의 PCS를 통합 제어하기 위해 채택한 듀얼코어 기반의 고성능 MCU TMS320F28377D를 이용하면 많은 PWM, ADC포트는 물론 충분한 연산시간 확보가 가능하다. 본 논문에서는 제안하는 하이브리드 ESS의 구성에 대해 소개하고 사용된 제어기의 구조, 각 PCS들을 통합 제어하기 위해 사용한 듀얼코어 기반의 DSP TMS320F28377D에 대해 설명하고자 한다.

• Journal of the Korean Ceramic Society
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• v.48 no.6
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• pp.499-503
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• 2011

Recently, variety of organic and inorganic hybrid materials have recently investigated as alternative routes to SiOC, $SiO_2$ thin film formation at low temperatures for applications in electronic ceramics. Specially, silicon based polymers, such as polycarbosilane, polysilane and polysilazane derivatives have been studied for use in electronic ceramics and have been applied as dielectric or insulating materials. In this study, Polycarbosilane(PCS), which Si-$CH_2$-Si bonds build up the backbone of the polymer, has been investigated as low-k materials using a solution process. After heat treatment at 350$^{\circ}C$ under $N_2$ atmosphere, chemical composition and dielectric constant of the thin film were $SiO_{0.27}C_{1.94}$ and 1.2, respectively. Mechanical property measured using nanoindentor shows 1.37 GPa.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.1
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• pp.45-53
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• 2013

Fuel cell power system is one of the most promising energy source for the alternative energy because it has unique advantages such as high energy density, no power drop during operation, and feasible to make compact size. However, due to very low response time, fuel cell is difficult to correspond to drastic load changes and start-up operation. For solving these problem, fuel cell power system must include energy storage device such as Li-Poly battery or super capacitor. Therefore, bi-directional DC-DC converter must be required for this storage device and fuel cell-PCS control. This paper presents a design and modeling of the bi-directional DC/DC converter. Firstly, we present modeling the boost and buck mode of the bi-directional converter through both PWM switch model and state space averaging technique. Secondly, in order to minimize output ripple and transient response overshoot, we have two identical DC-DC converters interleaved and adopt two-loop voltage-current controller. The proposed bi-directional DC-DC converter's modeling method and control design have been verified with computer simulation and experimentation.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.3
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• pp.459-464
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• 2023

The mobile house of this article is provided with stand-alone power system that uses photovoltaic energy and enables sensing and environmental monitoring. Excess power generated is stored in lithium batteries, which enable smooth operation of the mobile house even in environment in which solar energy cannot be used. The house has been designed that its systems can be operated continuously by diesel power generation even when photovoltaic energy cannot be generated due to long rainy season or heavy snow. BMS (batter management system) has been constructed for photovoltaic and power management, and monitors the charge/discharge and usage amount of photovoltaic energy. Various sensing data are recorded and transmitted automatically, and the design allows for wireless monitoring by means of computer and smartphone app. The container house proposed in this study enables efficient energy management by performing optimal energy operation in remote areas, parks, event venues, and construction sites where there is no system power source.