• 한국통신학회논문지
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• 제30권2A호
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• pp.90-97
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• 2005

일반적으로 DAB 시스템은 크게 stand-alone 방식과 PC/PDA 기반 방식으로 구분할 수 있다. PC/PDA 기반 방식은 stand-alone 방식에 비하여 휴대성이 떨어지나 연결된 PC/PDA의 메모리와 오디오/비디오 디코더 등 다양한 리소스를 이용할 수 있는 장점이 있다. 본 논문에서 구현한 DAB 수신기는 USB 인터페이스를 이용한 PC 기반의 수신기 시스템으로 USB 인터페이스 브리지는 FPGA와 EZ-USB 개발 키트를 이용하여 설계하였으며 실험을 위하여 기존의 stand-alone 방식의 DRK-026 DAB 수신기를 이용하여 PC 기반의 수신기를 구현하였다. USB 인터페이스 브리지는 시리얼 데이터를 USB 패킷 형태로 변환시켜주며 모든 신호는 하드웨어적으로 제어한다. 구현한 PC 기반 DAB 수신기의 동작 여부는 DAB 수신기로부터 오디오 데이터를 수신하여 USB 인터페이스를 통하여 PC에 전송한 후 디코딩 기능을 수행하는 것으로 확인하였다.

• 전기학회논문지
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• 제64권8호
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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.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2005년도 춘계학술대회
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• pp.64-67
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• 2005

A vibration monitoring system for a small size wind turbine (WIT) is established and operated. The monitoring system consists of monolithic integrated chip accelerometer for vibration monitoring, anemometers for wind data acquisition and auxiliary sensors for atmospheric data. Using the monitoring system, vibration response of a 6kW stand alone WIT generator is investigated. Acceleration data of the WIT tower under various operation condition is acquired in real time using LabVIEW and the data are remotely transferred from the test site to the laboratory in school by internet. Vibration response characteristics of the tower structure are diagnosed in the aspect of stability of W/T. Wind data and electrical power performance are also investigated with the stability problem.

• 대한전기학회논문지
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• 제41권4호
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• pp.369-378
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• 1992

This paper proposes a utility parallel processing inverter system, which consists of a voltage source PWM inverter, isolation transformer and a reactor linking the inverter to utility line. This system realizes following functions : (1) voltage phase frequency and amplitude synchronization between inverter and utility line at stand-alone mode. (2) current phase synchronization between inverter and load at parallel mode. Therefore, despite sudden increase in load current over setting point at stand-alone mode, inverter system can be transferred into parallel mode immediately without transient current. Furthermore, high frequency(18KHz) PWM control and sinusoidal filtering improve the inverter output waveform by eliminating high order harmonic components as well as low order. As a switching device, IGBT is used for high frequency switching and large current capacity.

• 한국태양에너지학회 논문집
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• 제35권6호
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• pp.9-15
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• 2015

In this paper, a parallel operating technique for the stand alone photovoltaic (PV) power conditioning system (PCS) is proposed. The proposed parallel operating technique can increase the power rating of the system easily. Also, it provide three-phase connection function. The proposed technique does not separated master and slave system. Also, it does not use the separated synchronization line. Therefore, the PCS can supply continuous power even if one of the PCS breaks down. This technique is composed of a phase locked loop (PLL) control, droop control, current limit control and etc. Experimental result obtained on 2-kW prototype to verify the proposed technique.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.969-972
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• 2003

This paper deal with a necessary factors for design grid connected photovoltaic system with stand-alone operation, and show simulation results of individual functions and multi- operation according to utility condition. Generally, photovoltaic system have only one operation of either stand-alone or line interactive, and have a isolation transformer for electrical isolation from utility therefore it is bulky, weighty, and a high price system as compared with usefulness. In this paper, A topology and algorithm adequate for lightweight, high efficiency, low price, multi function is selected and inquired into the validity using simulation of variable conditions.

• 전기학회논문지
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• 제61권8호
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• pp.1140-1147
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• 2012

This paper proposes the power management technology for stand-alone PV system to extend installation environment and coverage. The proposed power management technology in this paper can protect battery safeness from overcharge/discharge with keeping the proper SOC(State of Charge) and extend using time of system through estimation of operating power. The proposed power management technology in this paper is applied to Infra-free Variable Message Sign. And performance of power management technology in this paper was verified using simulation scenario.

• 전력전자학회논문지
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• 제20권2호
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• pp.115-121
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• 2015

Stand-alone inverter supplies constant voltage to loads. However, when a three-phase stand-alone inverter supplies unbalanced load, the generated output voltages also become unbalanced. The nonlinear characteristics of inverter dead time cause a more serious distortion in the output voltage. With unbalanced load, voltage distortion caused by dead time differs from voltage distortion under balanced load. Phase voltages in the stationary reference frame include unbalanced odd harmonics and then, d-q axis voltages in the synchronous reference frame have even harmonics with different magnitude, which are mitigated by the proposed multiple resonant controller. This study analyzes the voltage distortion caused by unbalanced load and dead time, and proposes a novel dead time compensation method. The proposed control method is tested on a 10-kW stand-alone inverter system, and shows that total harmonic distortion (THD) is reduced to 1.5% from 4.3%.

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2254-2261
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• 2018

This paper analyzes stability of current control in respect of four cases of battery energy storage system (BESS) in a stand-alone microgrid. The stand-alone microgrid is composed of BESS, diesel generator and controllable loads, where all of them have a rated power of 50kW. The four cases are considered as following: 1) BESS with a stiff grid 2) BESS with the diesel generator 3) BESS with passive damping + diesel generator 4) BESS with active damping + diesel generator, and their stabilities are analyzed in the frequency domain and discrete time domain. The comparative analysis for four cases are verified through simulation and experiments through demonstration site of the stand-alone microgrid, where the DC link is connected to a 115kW battery bank composed of 48 lead-acid batteries (400AH/12V). Experimental results show a good agreement with the analysis.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 F
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• pp.2565-2567
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• 1999

The output characteristics of solar cell vary with load and solar insolation. Therefore solar cell must always track maximum power point. If photovoltaic system is stand-alone. It is necessary to maintain for output of voltage source inverter. In this paper, stand-alone photovoltaic system consists of boost chopper and voltage source inverter. We make it to track maximum power point by revolution of solar cell array instead of detecting situation of sun in any conditions. And we prove that maximum power point tracking by revolution of solar cell array is better than fixed solar cell.