• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.285-287
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• 2009

When the laser diode is operated with continuous current, the light intensity from the laser diode deceases with time due to the temperature rise in the active layer. The phenomena, which is often called as DROOP, should be minimized in order to be used as a light source for the laser beam printer. We experimently examined the influences of the laser parameters such as threshold current, differential quantum efficiency on droop. It was found that decreasing the differential quantum efficiency of the laser diode is the effective way to minimize droop.

• Journal of Electrical Engineering and Technology
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• 제13권3호
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• pp.1060-1068
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• 2018

Droop control schemes have been widely employed in the control strategies for Multi-Terminal Direct Current (MTDC) system for its high reliability. Under the conventional DC voltage-active power droop control, the droop slope applies a proportional relationship between DC voltage error and active power error for power sharing. Due to the existence of DC network impedance and renewable resource fluctuation, there is inevitably a DC voltage deviation from the droop characteristic, which in turn results in inaccurate control of converter's power. To tackle this issue, a piecewise droop control with DC voltage dead band or active power dead band is implemented into controller design. Besides, an advanced droop control scheme with versatile function is proposed, which enables the converter to regulate DC voltage and AC voltage, control active and reactive power, get participated into frequency control, and feed passive network. The effectiveness of the proposed control method has been verified by simulation results.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 추계학술대회 논문집
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• pp.81-84
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• 2003

For increasing power of photovoltaic systems, serial and parallel connection needed. In parallel connection, a desirable characteristic of parallel-connected supply system is that individual converters share the load current equally and stably. The current sharing(CS) can be implemented using two approaches. The first one, known as a Droop method, and the other is Active current-sharing. In Droop method, current distribution characteristics relies on the high output impedance of each converter. This scheme is more simple and no need interconnections. but also has a disadvantages of degrading current sharing characteristics. In this paper, using droop method at multiful-parallel connection with it's convenience and simplicity.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.692-695
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• 2003

Generally, photovoltaic system is composed with several solar cell modules. For increasing power of photovoltaic systems, serial and parallel connection needed. A Desirable characteristic of a parallel supply system is that individual converters share the load current equally and stably. The current sharing(CS) can be implemented using two approaches. The first one, known as a droop method, relies on the high output impedance of each converter. and The second approach, known as active current-sharing techniques. In this paper, using droop method at parallel connection with it's convenience and simplicity.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2004년도 전력전자학술대회 논문집(2)
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• pp.910-913
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• 2004

This paper is about to develop a system to monitor speed droop rate characteristic of turbine governor for electric power plant. High quality electricity can be obtained, and so electricity supplier get more profit through it. Developed system presents basis of judgement of unusual system and proper maintenance time for the governor and power plant.

• 대한전자공학회논문지SP
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• 제42권4호
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• pp.153-158
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• 2005

본 논문에서는 software defined radio(SDR) 등의 디지털 RF/IF(Intermediate Frequency)에 사용되는 CIC 필터의 처짐 현상을 위한 보상 필터를 제안한다. 제안된 보상 필터는 근사적 선형 위상 특성을 가지며, interpolator/decimator의 기저 대역에서 가장 낮은 레이트로 동작하는 2차의 필터이므로 저연산량을 요구하므로 비용 효율적이다. 또한 처짐 현상을 보상하면서도 저지대역에서는 성능 열화가 거의 발생하지 않는다 예제를 통한 설계 및 성능 분석 결과, 제안된 보상 방법을 적용한 통신 시스템에 있어서 성능 향상을 보였고, 기존의 보상 방법과 비교하여 성능 및 메모리 사용량, 연산량에서 우수함을 보였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.362-364
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• 2003

Generally, photovoltaic system is composed a number of solar cells array. so, virtual implementation module for solar cell array is needed Parallel connection each module for extract the power. A desirable characteristic of a parallel supply system is that individual converters share the load current equally and stably. The current sharing(CS) can be implemented using two approaches. The first one, known as a droop method, relies on the high output impedance of each converter. and The second approach, known as active current-sharing techniques. In this paper, analyze for better control logic of parallel connecting virtual implements of solar cell at using droop method.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.734-738
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• 2002

In this paper, a novel wireless parallel operation algorithm of N+1 redundant UPS system with no control interconnections is presented. The load sharing of multiple UPS modules are controlled by Q-V droop and $P-\delta$ droop algorithm. This algorithm compensates for inverter parameter variation and line impedance imbalances with wireless auto-tuning method. And to increase the reliability of transient characteristic under parallel operation, a virtual injected Impedance is proposed to decrease a circulation current between inverter modules. Simulation results are provided to prove the novel wireless algorithm.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.987-993
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• 2003

The module UPS can flexibly implement expansion of power system capacities. Furthermore, it can be used to build up the parallel redundant system to improve the reliability of power system operation. To realize the module UPS, load sharing without interconnection among parallel connecting modules as well as a small scale and lightweight topology is necessary. In this paper, the three-arm converter/inverter is compared with the general full-bridge and half-bridge topology from a practical point of view and chosen as the module UPS topology. The switching control approaches based on a pulse width modulation of the converter and inverter of the system are presented independently The frequency and voltage droop method is applied to parallel operation control to achieve load sharing. Two prototype 3kVA modules are designed and implemented to confirm the effectiveness of the proposed approaches. Experimental results show that the three-arm UPS system has a high power factor, a low distortion of output voltage and input current, and good load sharing characteristic.

• KEPCO Journal on Electric Power and Energy
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• 제6권2호
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• pp.123-127
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• 2020

KEPCO has installed Frequency Regulation ESS (FR ESS) of 376 MW since 2015. Frequency Regulation is ancillary service to support stabilizing system frequency, which is divided into governor free and automatic generation control. KEPCO operates FR ESS as governor free application and leads FR ESS market with capability of diverse demonstration and operation experiences. To expand FR ESS role during transient states of power system, KEPCO has extended operating time of charging and discharging. KEPCO has also changed speed droop lower than before to improve contribution on frequency compensation, and acquired much experiences of differentiating bad cells from others. Based on these technologies and know-hows, KEPCO Research Institutes received request of feasibility study and technical cooperation for overseas FR ESS business. This paper suggests the simple and practical method for making technological feasibility study of FR ESS.