• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.794-795
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• 2011

The DC side voltage and current of a HVDC transmission system are directly affected by non-linear switching devices such as the thyristor valve which causes real power losses, even under the superconducting conditions of a high temperature superconducting (HTS) power cable. This paper deals with the development of miniaturized superconducting DC cable system. The authors designed and fabricated two thyristor converters for DC transmission system. One is operated as a rectifier and the other is an inverter. The HTS model cable was connected between the DC side of the rectifier and inverter. Real DC transport current and voltage were applied to the miniaturized HTS DC cable. Experimental results are discussed in detail.

• Journal of Advanced Marine Engineering and Technology
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• 제36권5호
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• pp.662-673
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• 2012

This study introduces a condition diagnosis technique for a turbine governor system. The governor system is an important control system to handle turbine speed in a nuclear power plant. The turbine governor system includes turbine valves and stop valves which have their own functions in the system. Because a turbine governor system is operated by high oil pressure, it is very difficult to maintain under stable operating conditions. Turbine valves supply oil pressure to the governor system for proper operation. Using the pressure variation of turbine and governor valves, operating conditions of the turbine governor control system are detected and identified. To achieve automatic detection of valve status, time-based and frequency-based analysis is employed. In this study, a new approach, wavelet decomposition, was used to extract specific features from the pressure signals of the governor and stop valves. The extracted features, which represent the operating conditions of the turbine governor system, include important information to control and diagnose the valves. After extracting the specific features, decision rules were used to classify the valve conditions. The rules were generated by a decision tree algorithm (a typical simple method for data-based rule generation). The results given by the wavelet-based analysis were compared to detection results using time- and frequency-based approaches. Compared with the several related studies, the wavelet transform-based analysis, the proposed in this study has the advantage of easier application without auxiliary features.

• 한국정밀공학회지
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• 제26권1호
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• pp.112-119
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• 2009

An automatic transmission of construction equipment is controlled by hydraulic and electronic system for doing in various functions like as shifting and operation. The shifting is operated by the engaged and disengaged clutch motion from hydraulic power. On the shifting process, suitable pressure control to the clutch is required for smooth shifting. Hydraulic control system in the automatic transmission is divided by the pilot control type and the direct control type greatly. The direct control type has an advantage than the pilot control type. Because the structure is simple, the design and the manufacture are having less troubles and the system can be maximized precision pressure control. However, the excellent performance proportional control valve should be used to achieve proper control-ability. In this study, the dynamic analysis model composing the automatic transmission and hydraulic system for forklift truck is presented to simulate the characteristics of hydraulic system about the direct control type. That model is verified the validity compared the results of the testing examination. Parameters of input signal are analyzed to reduce the output torque according to input control signal is affected in shifting characteristic.

• Nuclear Engineering and Technology
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• 제35권3호
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• pp.179-190
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• 2003

The multiple steam generator tube rupture (SGTR) event scenario with available safety systems was experimentally and analytically evaluated. The experiment was conducted on the large scaled test facility to simulate the multiple SGTR event and investigate the effectiveness of operator actions. As a result, it indicated that the opening of pressurizer power operated relief valve was significantly effective in quickly terminating the primary-to-secondary break flow even for the 6.5 tubes rupture. In the analysis, the recent version of RELAP5 code was assessed with the test data. It indicated that the calculations agreed well with the measured data and that the plant responses such as the water level and relief valve cycling in the damaged steam generator were reasonably predicted. Finally, sensitivity study on the number of ruptured tubes up to 10 tubes was performed to investigate the coolant release into atmosphere. It indicated that the integrated steam mass released was not significantly varied with the number of ruptured tubes although the damaged steam generator was overfilled for more than 3 tubes rupture. These findings are expected to provide useful information in understanding and evaluating the plant ability to mitigate the consequence of multiple SGTR event.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 정기총회 및 창립40주년기념 학술대회 학회본부
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• pp.362-366
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• 1987

The amount of inflowing Air into the boiler has controlled by manipulating the opening of valve, damper and vane, as fan operated by induction motor operats at constant speed, but these control methods are not efficient. Thus VVVf(Variable Voltage Variable Frequency) control of fan has selected to improve efficiency and to acquire power savings. Control system of Air Flow is affected by nonlinearity caused by load variation, vane opening, etc. The analysis of control parameter causing nonlinearity is needed to acquire optimal control and excellent transient response. This paper provides modeling of boiler with various load conditions and vane opening, and analysis of this system.

• 동력기계공학회지
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• 제10권3호
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• pp.5-10
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• 2006

In a conventional and lean operating engine, the state of mixture is very important in the combustion and emission characteristics. Lean operation is known to decrease the formation while maintaining a good fuel economy, but the unstable operation due to misfire and erratic combustion prevents engines from being operated at very lean mixtures, so both combustion rates and exhaust emission formation need to be satisfied comparably. In this study, it is designed and experimented the modified engine, and analyzed the combustion and exhaust emission according to the change of engine speed and with adding ozone. The conclusions were drawn out and enumerated as follows. 1. At the experimental result of automobile diesel engine, it has been verified that the formation of particulate matter(PM) gas is able to be lower with the addition of optimum quantities of ozone. 2. Carbon monoxide(CO) was formed by the lack of oxygen and the thermal dissociation in the combustion process. Therefore, with the change of swirl valve's position and addition of oxygen and ozone, CO formation was decreased by the increasing of excessive O2, but it was increased by the temperature of combustion gas growing higher. As a result of the two effects, CO formation was decreased in this study. 3. Hydrocarbon(HC) was formed by the lack of O2, and the flow of mixture in cylinder. According to opening of the swirl valve and adding the oxygen and ozone, hydrocarbon gas was decreased by 20%, 9%, and 27.5%, respectively. 4. Nitric oxides($NO_x$) was strongly affected by the combustion gas temperature. As a result of respectively experimental conditions, $NO_x$ formation was increased about 20% due to (be the) high(er) combustion gas temperature.

• 한국인터넷방송통신학회논문지
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• 제16권1호
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• pp.253-262
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• 2016

본 논문은 경제급전 최적화 문제에 균형-교환 방법을 제안하였다. 제안된 알고리즘은 모든 발전기를 가능한한 밸브지점으로 운영한다고 가정한다. 초기치로 최대 발전량 $P_i{\leftarrow}P_i^{max}$로 설정하고, 각 발전기의 밸브지점 $v_k$까지 발전량을 감소시켰을 때의 평균 발전단가 $c_i=\frac{F(P_i)-F(P_{iv_k})}{(P_i-P_{iv_k})}$가 최대가 되는 $_{max}c_i$ 발전기 i의 발전량을 밸브지점 발전단가 $P_{iv_k}$로 감소시켰으며, ${\Sigma}P_i-P_d$ > 0이면 $c_i=F(P_i)-F(p_i-1)$의 $_{max}c_i$ 발전기 발전량을 $P_i{\leftarrow}P_i-1$로 감소시켜 ${\Sigma}P_i=P_d$의 균형을 맞추었다. 다음으로, $_{min}\{_{max}(P_i-P_i^{min}),\;_{max}(P_i^{max}-P_i)\}$>${\alpha}{\geq}10$의 범위에 대해 "-10" 간격으로 감소시키는 성인걸음법으로, 10>${\alpha}{\geq}1$ 범위에 대해서는 "-1"의 아기걸음법으로, $P_i=P_i{\pm}{\alpha}$에 대한 $_{max}[F(P_i)-F(P_i-{\alpha})]$>$_{min}[F(P_j+{\alpha})-F(P_j)]$, $i{\neq}j$이면 $P_i=P_i-{\alpha}$, $P_j=P_j+{\alpha}$로 발전량을 교환하는 방법으로 최적화를 수행하였다. 다음으로 ${\alpha}=\text{0.1, 0.01, 0.001, 0.0001$에 대해 미세한 교환을 수행하였다. 동적 경제급전 문제의 시험 사례에 제안된 알고리즘을 적용한 결과 기존의 휴리스틱 알고리즘 최적화 발전비용을 크게 감소시켜 경제적인 이익을 극대화 시켰다.

• 융합신호처리학회논문지
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• 제16권2호
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• pp.74-82
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• 2015

본 논문에서는 BM 활성수를 생산하는 BM 활성수 플랜트 공정 제어시스템 모델을 제안하고, 다음과 같은 기능을 가진 BM 활성수 플랜트 공정 제어기를 개발 하였다. 첫 번째 기능으로는 먼저 부로와가 과부하가 걸렸을 때, 과전류 감지기가 동작하여 일정시간 부로와를 정지시킨 후 재 기동 하도록 하였다. 두 번째는 정전시 유도조에서 퇴비투입조로의 순환을 막기 위해 전동밸브가 정전시 자동으로 닫히는 기능을 부가함으로서 볼밸브의 고장으로 인한 퇴비투입조의 누수를 막을 수 있다. 세 번째는 생산된 활성수를 농축조에서 4개의 저장조로 자동으로 이송할 수 있는 기능을 부가하여 활성수 생산량을 자동 관리 하였다. 그리고 BM 활성수 플랜트 공정제어기 신호측정 시험장치를 개발하여 제작한 BM 활성수 플랜트 공정 제어기가 설계한 사양대로 잘 동작하는지 확인 하였다. 본 연구는 BM 활성수 플랜트 공정제어기를 견실한 저가의 시퀀서 제어방식 기반의 공정 제어기를 개발하여 시스템의 안정성과 효율성의 향상 및 운전관리 비용의 절감을 꾀할 수 있으리라 기대된다.

• 로봇학회논문지
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• 제16권2호
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• pp.86-93
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• 2021

This paper proposes a controller to regulate the supply pressure of the hydraulic power unit (HPU) for driving a bipedal robot. We establish flow rate models for charging accumulator, actuating joints and leaking from actuators and spool valves. This determines the pump driving motor speed to satisfy the demanded flow rate for operating the bipedal robot without the energy loss caused by the bypass through a pressure regulating valve. We apply proposed controller to an onboard HPU mounted on top of bipedal robot platform with twelve degrees of freedom. We implement air-walking motion and squat motion which require variable flow rate to the bipedal robot. Through this experiment, the energy efficiency of proposed controller was verified by comparing the electric energy consumed when the controller was applied and when the pump operated at constant speed. We also shows the capability of the HPU's control performance to regulate supply pressure.

• 전기학회논문지
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• 제62권1호
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• pp.143-148
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• 2013

When the fault occurs in power system, the fault-current exceeds breaking capacity of the circuit breaker. So, reliablity of the power system is decreased sharply. Superconducting fault-current limiter (SFCL) is operated without impedance in normal state. The fault-current is limited by its impedance during the fault condition. However, the SFCL has several weak points such as huge size, high-price, liquid-nitrogen operation for the real power system. In this paper, We suggested the high-speed interrupter to limit the fault-current in case of the single line-to-ground fault. In addition, we compared the high-speed interrupter with the SFCL to ensure the operation reliability. The proposed interrupter detected the fault-current through the CT, and the power was supplied by operation of the SCR control system. In this experiment, the power of high-speed interrupter was applied after the 4.8[msec] from fault instant. The on-off operation of the interrupter was started after half-cycle from the fault. The fault-current was flowed into the impedance element by the switching operation of the high-speed interrupter. So, the fault current was limited within one cycle, and then it didnt exceed the capacity of a circuit breaker. We confirmed that there was slight difference between the SFCL with high-speed interrupter in terms of limiting-time of the fault-current and switching speed of the SCR. The high-speed interrupter was considered to be more efficient than the SFCL in size, cost or reliability.