• Proceedings of the Membrane Society of Korea Conference
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• 2005.11a
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• pp.124-124
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• 2005

• Proceedings of the Optical Society of Korea Conference
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• 2004.02a
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• pp.152-153
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• 2004

• The KSFM Journal of Fluid Machinery
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• v.15 no.6
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• pp.18-24
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• 2012

This study simulated the operation of a steam injected gas turbine combined heat and power (CHP) system. A full off-design analysis was carried out to examine the change in the turbine blade temperature caused by steam injection. The prediction of turbine blade temperature was performed for the operating modes suggested in the previous study where the limitation of compressor surge margin reduction was analyzed in the steam injected gas turbine. It was found that both the fully injected and partially injected operations suggested in the previous study would cause the blade temperature to exceed that of the pure CHP operation and the under-firing operation would provide too low blade temperature. An optimal operation was proposed where both the turbine inlet temperature and the injection amount were modulated to keep both the reference turbine blade temperature and the minimum compressor surge margin. The modulation was intended to maintain a stable compressor operation and turbine life. It was shown that the optimal operation would provide a larger power output than the under-firing operation and a higher efficiency than the original partially injected operation.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.2
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• pp.233-238
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• 2018

This paper proposes a seamless MPPT operation mode transfer method of photovoltaic system. The photovoltaic system consists of a DC-DC boost converter, a DC-Link, and a 3-level neutral point clamp (NPC) type inverter. The PV voltage fluctuates due to the output characteristics of the solar pane1 depending on the irradiation amount and the temperature. The photovoltaic system requires seamless MPPT mode transfer method that the discontinuity does not occur in order to supply the stable power to system without affecting the fluctuation of the PV voltage. MPPT operation is divided into two modes by the voltage reference. Under the condition that the PV voltage is below 650V, the DC-DC boost converter performs MPPT through duty control based on perturb & observe (P&O) method, and the inverter conducts DC-link voltage and grid current controls in synchronous reference frame. On the other hand, when the PV voltage exceeds above 650V, inverter performs MPPT in accordance with the variation of DC-link voltage control while the converter stops operating. Two MPPT operation modes is smoothly transferred through the proposed method that DC-link voltage or grid current commands are appropriately adjusted from the certain criteria. The feasibility of the MPPT operation mode transfer method is verified using a 10kW solar photovoltaic system, experimental results have good performances that the fluctuation of PV current is reduced to 100%.

• Membrane Journal
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• v.21 no.3
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• pp.263-269
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• 2011

In the operation of submerged membrane-coupled sequencing batch reactor, the effect of filling step on the removal efficiency and filtration performance were investigated. Two sets of operation modes, the filling step located in the beginning of aerobic step (Mode-1) and the beginning of anoxic step (Mode-2), during 89 days were conducted. There was no wide difference in the COD removal and filtration performance between two sets of operation modes. But in the removal efficiency of nutrients (total nitrogen and total phosphorous), Mode-2 was more effective than Mode-1. In the case of Mode-2, average removal efficiencies of COD, total nitrogen, and total phosphorous were 99.1, 73.3, and 77.3%, respectively.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.73-75
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• 2020

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.636-641
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• 1998

In this paper, operation characteristics of the Zero-voltage-Switching(ZVS) mode and Non-Zero-Voltage-Switching (NZVS) mode of the active clamp (ACL) forward converter are compared through the loss analysis. The losses of semiconductor devices, transformer and passive elements of the converter are analyzed and compared for each type of operation mode. In order to verify the validity of the analysis, we have built a 50W ACL forward converter and measured the losses of the converter. From the experiment it is known that the ACL forward converter shows nearly same loss distribution for both of operation modes

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.12
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• pp.676-681
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• 2002

This paper presents the implementation and experimental investigation of sensorless speed control for a variable-speed PMSM(Permanent Magnet Synchronous Motor) in super-high speed compressor operation. The proposed control scheme consists of two different sensorless algorithms to guarantee the reliable starting operation in low speed region and full torque characteristics using the vector control in high speed region. An automatic switching technique between two control modes is proposed to minimize the speed and torque pulsation during the switching instant of control mode. A testing system of 3.3㎾ PMSM has been built and 90% load test results at 7000r/min are presented to examine the feasibility of proposed sensorless control scheme.

• The KSFM Journal of Fluid Machinery
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• v.14 no.6
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• pp.68-75
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• 2011

This study simulated the effect of steam injection on the performance and operation of a gas turbine combined heat and power (CHP) system. A commercial simple cycle gas turbine was analyzed. A full off-design analysis was carried out to investigate the variations in not only engine performance but also the operating characteristics of the compressor caused by steam injection. Variation in engine performance and operation characteristics according to various operation modes were examined. First, the impact of full steam injection was investigated. Then, operations aiming to guarantee a minimum compressor surge margin, such as under-firing and partial steam injection, were investigated. The former and latter were turned out to be relatively superior to each other in terms of power and efficiency, respectively.

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.34-36
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• 2006

In this paper, we will treat the diagnosis problem to accurately determine fault types. The judgement of fault types is accomplished by observing the cluster newly formed with faults and clustering the input current waveforms to intrinsically show the conditions with the dignet that is a clustering algorithm. The types of input current waveforms are, however, constrained during normal operation, though it considers the load character. In case of faults. new clusters are generated outside the clusters. which appear during normal operation, because the input current waveforms of the induction motor are generated by the type which is not observed in case of faults. The diagnosis about the types of faults is essential to building a fault tree about the induction motor, and it removes the causes of the faults using a fuzzy logic. We, first, constitute a fault tree, which connects with the parts and the entire system of the induction motor, and investigate fault modes which can be generated from the fault tree and the relationship of the cause and the effect of each part (of the motor). Also, we distinguish the faults of each part by means of inducing the said of fuzzy relation equations encapsulating the relationship of the fault modes and each part.