• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.673-674
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• 2011

정부의 녹색성장 정책에 의해 배전계통에 태양광, 풍력발전 등 분산전원의 설치가 급증함에 따라 기존의 배전계통의 조류의 방향 및 고장전류, 부하전류가 변화되어 배전계통의 보호협조 운용상에 여러 가지 문제점들이 발생할 가능성이 커지고 있다. 특히 분산전원연계시 임피던스 병렬화로 보호기기에 흐르는 사고전류가 감소하는 분류효과가 발생할 가능성이 있다. 따라서 본 논문에서는 분산전원이 연계된 경우 보호협조를 검토하기 위한 양방향 보호협조 평가프로그램을 이용하여 분산전원이 연계된 경우 계통에서 발생할 수 있는 문제점 중 분류 효과로 인한 보호기기의 부동작 사례를 시뮬레이션하고, 그 결과를 분석하여 본 프로그램의 유용성을 확인하였다.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.209-211
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• 2009

A digital grid synchronization technique is needed for distributed generation system to make output current sinusoidal even if the grid voltage is distorted by harmonics. In this paper, a digital grid synchronization technique based on adaptive notch filter is proposed. The analysis of proposed technique is performed through the consideration of grid synchronization technique based on PLL and FLL, and the validity of the proposed method was confirmed by simulation results.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.333_335
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• 2009

It is expected, in the near future, that the use of distributed generation systems should be increased considerably. In this case, distance relay algorithm should be developed in the manner that it can reduce the error due to the in-feed effect. This paper presents a method to consider the fault current rushed from the remote end of a line. In the steady-state, the relays in both ends exchange the voltages of upper nodes. If a fault is perceived, the relay calculates fault location taking the fault current from the remote end by using voltage data of the remote ends obtained just before the fault. Even though this method has inevitable error, it can show more precise fault allocation. The suggested method is applied to a typical transmission system with two power sources in both ends to verify its effectiveness.

• Proceedings of the KIEE Conference
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• 2006.11a
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• pp.87-89
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• 2006

현재 전력계통분야에서 신재생에너지원을 이용한 분산전원 (DG, Distributed Generation)이 확대 보급됨에 따라 이에 대한 기술의 높은 신뢰성 및 경제성이 높아지고 있는 시점이다. 이에 따라 분산전원의 효율 적운용을 위한 모니터링 장치의 필요성이 또한 증대되고 있다. 본 논문에서는 신재생에너지원 중 대표적인 태양 광발전시스템의 현재 상태 (전압 전류, 전력, 위상, 주파 수)를 계통의 모니터링을 위해 제작한 ATmega 128(AVR)이 내장된 Power Line Data Acquisition Board와 현재 널리 통용되는 GUI시스템인 $LabVIEW^{TM}$를 이용하여 컴퓨터를 통한 태양광발전시스템을 모니터링 하는 프로그램을 구현하고자 한다.

• Proceedings of the KIEE Conference
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• 2006.11a
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• pp.228-230
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• 2006

국내 배전계통에 분산전원의 설치가 증가하고 있고, 분산전원 중 효율성과 경제성이 뛰어난 열병합 발전기의 보급이 국내를 비롯한 선진국에서 늘어나고 있는 추세이다. 그에 따라 독립적으로 전력을 생산할 수 있는 분산전원 운영자들이 증가하고 있다. 분산전원 운영자들은 한국전력공사가 제시하는 연계점 역률 0.9이상을 만족시키도록 분산전원을 운영해야하고, 동시에 자신의 이익을 최대화한다. 본 논문에서는 연계점의 역률을 고려하여 분산전원을 운영하였을 때 분산전원 운영자의 이익을 분석하였다. 연계점의 역률을 변화하여 변화된 역률이 분산전원 운영자의 이익에 어떤 영향을 주는지 연구하였다.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.266-267
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• 2017

To synchronize the distributed generation (DG) unit with the grid, the voltage sensors are generally employed to obtain the grid phase angle. This paper presents an observer-based voltage sensorless control scheme for a three-phase inverter connected to the grid through an LCL filter. The proposed control scheme consists of an augmented state observer and a feedback controller. The augmented state observer is used to estimate the grid voltages and states of the inverter system, which are then employed to determine the grid voltage angle and to construct the feedback controller. As a result of using the observer, only the grid current sensors are required to accomplish the control scheme. The simulation results are given to prove the validity of the proposed control scheme.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.9
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• pp.108-113
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• 2013

Change of supply voltage, customer load, output of distributed generation, etc cause voltage change in distribution system. OLTC and SVR are usually used to supply normal voltage at customer. But usage of these devices is inefficient and uneconomical in certain circumstances. To solve this problem, new pole transformer which has automatic tap changer is developed. The transformer changes tap when voltage changes. And it has latch switch and reactor for supplying power without outage. To verify normal operation of tap changer, test is conducted. SVR and 50kVA load is used for test.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.121-122
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• 2015

본 논문에서는 기존의 불검출영역(Non Detection Zone; NDZ) 해석보다 수식적으로 더욱 정밀하게 NDZ를 분석한다. 또한, 이런 NDZ를 벗어나게 하는 최소 이득의 Positive-feedback loop를 가지는 새로운 단독운전 방지기법을 설계하고, 이를 시뮬레이션과 실험을 통해 단독운전 검출 성능을 검증하고 제안하는 기법이 전력품질에 끼치는 영향을 분석한다.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.1
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• pp.59-68
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• 2009

Fuel cell generators as the distributed generation system with a few hundred watt$\sim$a few hundred kilowatt capacity, can supply the high quality electric power to user as compared with conventional large scale power plants. In this paper, PEMFC(polymer electrolyte membrane fuel cell) generator as micro-source is modelled by using PSIM simulation software and DSP based fuel cell hardware simulator based on the PSIM simulation model is implemented. The relation of fuel cell voltage and current(V-I curve) is linearized by first order function on the ohmic area in voltage-current curve of fuel cell. The implemented system is composed of a PEMFC hardware simulator, an isolated full bridge dc boost converter, and a 60[Hz] voltage source PWM inverter. The voltage-current-power(V-I-P) characteristics of the implemented fuel cell hardware simulator are verified in load variation and transient state and the 60[Hz] output voltage sinusoidal waveform of the PWM inverter is investigated under the resistance load and nonlinear diode load.

• 한국태양에너지학회:학술대회논문집
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• 2009.04a
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• pp.102-108
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• 2009

Fossil power plants firing lower grade coals or equipped with modified system for NOx controls are challenged with maintaining good combustion conditions while maximizing generation and minimizing emissions. In many cases significant derate, availability losses and increase in unburned carbon levels can be attributed to poor combustion conditions as a result of poorly controlled local fuel and air distribution within the boiler furnace. In order to develop a on-line combustion tuning system, field test was conducted at operating power boiler. During the field test the exhaust gases' $O_2$, NOx and CO was monitored by using a spatially distributed monitoring grid located in the boiler's high temperature vestibule and upper convective back-pass region. At these locations, the flue gas flow is still significantly stratified, and air in-leakage is minimal which enables tracing of poor combustion zones to specific burners and over-fire air ports. using these monitored information we can improving combustion at every point within the furnace, therefore the boiler can operate at reduced excess $O_2$ and gas temperature deviation, reduced furnace exit gas temperature levels while also reducing localized hot spots, corrosive gas conditions, slag or clinker formation and UBC. Benefits include improving efficiency, reducing NOx emissions, increasing output and maximizing availability. Discussion concerning the reduction of greenhouse gases is prevalent in the world. When taking a practical approach to addressing this problem, the best way and short-term solution to reduce greenhouse gases on coal-fired power plants is to improve efficiency. From this point of view the real time optimized combustion tuning approach is the most effective and implemented with minimal cost.