• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 B
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• pp.1091-1093
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• 2001

The power semiconductor is widely used in the power plant or industrial field because of genealization and enlargement. It has been controlled and operated according to its own control method. Especially in case of Power plant, it plays a major role in AVR(Automatic Voltage Regulator) or electro chlorination control circuits. Generally, they used in Analog control system at above field. But each SCR current value is different because of load unbalance or switching characteristic variations, it may cause power plant unit trip or system disorder according to SCR element burn out or bad operating condition. Therefore, in this paper a development of 3 phase current balance control algorithm is described. it gets over the past analog control system limit, controls SCR gate firing angle for 3 phase current balance.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 B
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• pp.1088-1090
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• 2001

In general, Power SCR(Silicon Controlled Rectifier) is most widely used in Power Plant as well as Industrial field. It has been controlled and operated according to its own control method. Especially, in case of Power plant, it plays a major role in AVR(Automatic Voltage Regulator) or electro chlorination control circuits. Generally, they used in Analog control system at above field. But each SCR current value is different because of load unbalance or switching characteristic variations, it may cause power plant unit trip or system disorder according to SCR element burn out or bad operating condition. Therefore, in this paper a development of 3 phase current balance control unit is described, it gets over the past analog control system limit, uses DSP(Digital signal processor) had high speed response, controls SCR gate firing angle for 3 phase current balance.

• Environmental Engineering Research
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• 제20권2호
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• pp.155-161
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• 2015

Experimental research shows that the nitric oxides ($NO_X$) concentration track at the outlet of selective catalytic reduction (SCR) catalyst with a transient variation of Adblue dosage has a time delay and it features a characteristic of resistance-capacitance (RC). The phenomenon brings obstacles to get the simultaneously $NO_X$ expected to be reduced and equi-molar ammonia available to SCR reaction, which finally inhibits $NO_X$ conversion efficiency. Generally, engine loads change frequently, which triggers a rapid changing of Adblue dosage, and it aggravates the air quality that are caused by $NO_X$ emission and ammonia slip. In order to increase the conversion efficiency of $NO_X$ and avoid secondary pollution, the paper gives a comprehensive analysis of the SCR system and tells readers the key factors that affect time delay and RC characteristics. Accordingly, a map of time delay is established and a solution method for time constant and proportional constant is carried out. Finally, the paper accurately describes the input-output state relation of SCR system by using "variable RC model with time delay". The model can be used for a real-time correction of Adblue dosage, which can increase the conversion efficiency of $NO_X$ in SCR system and avoid secondary pollution forming. Obviously, the results of the work discover an avenue for the SCR control strategy.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.659-673
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• 2021

This study aims to investigate the impact of the High Pressure Selective Catalytic Reduction system (SCR-HP) on a large marine two-stroke engine performance parameters by employing thermodynamic modelling. A coupled model of the zero-dimensional type is extended to incorporate the modelling of the SCR-HP components and the Control Bypass Valve (CBV) block. This model is employed to simulate several scenarios representing the engine operation at both healthy and degraded conditions considering the compressor fouling and the SCR reactor clogging. The derived results are analysed to quantify the impact of the SCR-HP on the investigated engine performance. The SCR system pressure drop and the cylinder bypass valve flow cause an increase of the engine Specific Fuel Oil Consumption (SFOC) in the range 0.3-2.77 g/kWh. The thermal inertia of the SCR-HP is mainly attributed to the SCR reactor, which causes a delayed turbocharger response. These effects are more pronounced at low engine loads. This study supports the better understanding of the operating characteristics of marine two-stroke diesel engines equipped with the SCR-HP and quantification of the impact of the components degradation on the engine performance.

• 전기의세계
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• 제19권4호
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• pp.1-11
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• 1970

It is well known that solid-state devices like inverter and converter made by transistor and other semi-conductors are widely used for the purpose of motor speed control in industrial fields. This paper is devoted primarily to a study of Trial Manufacturing of Solid-state Frequency Converter by means of single-phase bridge-type SCR inverter. The principle of the trial product belongs to AC-DC-AC conversion system. The voltage to be impressed to the motor in case of speed control by frequency conversion method is necessary to be proportional to frequency. It also requires the frequency and voltage are independent to hte load variation. In order to meet above requests required to motor speed control., the trial product introduced the open loop system in the frequency setting and closed loop system in the voltage setting. The trial product showed the favorable performance characteristics in speed control of singlephase fractional horsepower motor from 45HZ through 80HZ.

• 한국자동차공학회논문집
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• 제19권5호
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• pp.118-124
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• 2011

To reach the Euro-6 regulations of PM and $NO_x$ for light-duty diesel vehicles, it will be necessary to apply the CDPF and the de-$NO_x$ catalyst. The described system consists of a catalytic configuration, where the CDPF is placed downstream of the diesel engine and followed by a urea injection unit and a urea-SCR catalyst. One of the advantages of this system configuration is that, in this way, the SCR catalyst is protected from PM, and both white PM and deposits become reduced. In the urea-SCR system, the injection control of reductant is the most important thing in order to have good performance of $NO_x$ reduction. The ideal ratio of $NH_3$ molecules to $NO_x$ molecules is 1:1 based on $NH_3$ consumption and having $NH_3$ available for reaction of all of the exhaust $NO_x$. However, under the too low and too high temperature condition, the $NO_x$ reduction efficiency become slower, due to temperature window of SCR catalyst. And space velocity also affects to $NO_x$ conversion efficiency. In this paper, rig-tests were performed to evaluate the effects of $NO_x$ and $NH_3$ concentrations, gas temperature and space velocity on the $NO_x$ conversion efficiency of the urea-SCR system. And vehicle test was performed to verify control strategy of reductatnt injection. The developed control strategy of reductant injection was improved over all $NO_x$ reduction efficiency and $NH_3$ consumption in urea-SCR system. Results of this paper contribute to develop urea-SCR system for light-duty vehicles to meet Euro-5 emission regulations.

• 한국정보과학회논문지:소프트웨어및응용
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• 제31권6호
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• pp.750-759
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• 2004

원자력 발전소의 디지털 제어 시스템에 적용되는 소프트웨어는 안전성이 중요시되는 safety-critical 소프트웨어로, 충분한 수준의 안전성을 보장하기 위해서 여러 기법들이 적용되고 있다. 특히, 정형명세 기법은 개발의 초기 단계에서 소프트웨어 요구 사항들을 명확하고 완전하게 명세 하도록 유도함으로써 안전성을 크게 향상시킬 수 있는 기법으로 인정받고 있다. 본 논문에서는 원자력 발전소 디지털 제어 시스템 소프트웨어의 요구 사항 명세에 적합하도록 개발된 정형명세 기법인 NuSCR을 논의한다. 또한, 개발된 NuSCR의 적용성을 검토하기 위해, 현재 KNICS 사업단에서 개발중인 발전소보호계통 소프트웨어의 요구사항을 정형 명세 한 경험을 소개하고 있다. 또한, 원자력 도매인에 특화된 정형명세 기법인 NuSCR의 우수성도 실례를 들어 설명하고 있다.

• 한국자동차공학회논문집
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• 제19권2호
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• pp.98-104
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• 2011

The introduction of a diesel engine into the passenger car and light duty applications in the United States involves significant technical challenges for the automotive makers. This paper describes the SCR System optimization procedure for such a diesel engine application to meet Tier2 Bin5 emission regulation. A urea SCR system, a representative $NO_x$ reduction after-treatment technique, is applied to a 3.0 liter diesel engine. To achieve the maximum $NO_x$ reduction performance, the exhaust system layout was optimized using series of the computational fluid dynamics and the urea distribution uniformity test. Furthermore a comprehensive simulation model for the key factors influencing $NO_x$ reduction performance was developed and embedded in the Simulink/Matlab environment. This model was then applied to the urea SCR system and played a key role to shorten the time needed for SCR control parameter calibration. The potential of a urea SCR system for reducing diesel $NO_x$ emission is shown for FTP75 and US06 emission standard test cycle.

• Journal of Advanced Marine Engineering and Technology
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• 제31권3호
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• pp.235-242
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• 2007

This paper discusses dynamic characteristics of a urea-SCR (Selective Catalytic Reduction) system. The urea flow rate to improve NOx conversion efficiency is generally determined by parameters such as catalyst temperature and space velocity. The urea-SCR system was tested in the various engine operating conditions governing the raw NOx emission levels, space velocity. and SCR catalyst temperature. These experiments include cold-transients to determine catalyst light-off temperature and urea flow rate transients. Likewise. ammonia storage dynamics was also investigated. The cold-transient results indicate the light-off temperature of the catalysts used in these experiments was $200-220^{\circ}C$. The ammonia storage and urea flow rate transients all indicate very slow dynamics (on the order of seconds) which presents control challenges for mobile applications. The results presented in this paper should provide an excellent starting point in developing a functional in-vehicle urea-SCR system.

• 한국자동차공학회논문집
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• 제19권2호
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• pp.50-56
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• 2011

To meet the NOx limit without a penalty of fuel consumption, Urea-SCR system is currently regarded as promising NOx reduction technology for diesel engines. SCR system has to achieve maximal NOx conversion in combination with minimal $NH_3$ slip. In this study, map based open loop control for urea injection was developed and assessed in the European Transient Cycle (ETC) for heavy duty diesel engine. The basic urea quantity set-value which was calculated using the look up tables of engine out NOx, exhaust flow rate and optimum NSR resulted in NOx reduction of 80% and the average $NH_3$ slip of 24 ppm and maximum of 79 ppm. In order to reduce $NH_3$ slip, $NH_3$ storage control algorithm was applied to correct the basic urea quantity and reduced $NH_3$ slip levels to the average 15 ppm and maximum 49 ppm while keeping NOx reduction of 76%. With high and increasing SCR temperature, the $NH_3$ storage capacity decreases, which leads to $NH_3$ slip. The resulting $NH_3$ slip peak can be avoided by stopping or significantly reducing the urea injection during the SCR temperature gradient is over $30^{\circ}C/min$.