• Nuclear Engineering and Technology
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• v.46 no.6
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• pp.725-736
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• 2014

It is very important to detect and identify small anomalies and component failures for the safe operation of complex and large-scale artifacts such as nuclear power plants. Each diagnostic technique has its own advantages and limitations. These facts inspire us not only to enhance the capability of diagnostic techniques but also to integrate the results of diagnostic subsystems in order to obtain more accurate diagnostic results. The article describes the outline of four diagnostic techniques developed for the condition monitoring of the fast breeder reactor "Monju". The techniques are (1) estimation technique of important state variables based on a physical model of the component, (2) a state identification technique by non-linear discrimination function applying SVM (Support Vector Machine), (3) a diagnostic technique applying WT (Wavelet Transformation) to detect changes in the characteristics of measurement signals, and (4) a state identification technique effectively using past cases. In addition, a hybrid diagnostic system in which a final diagnostic result is given by integrating the results from subsystems is introduced, where two sets of values called confidence values and trust values are used. A technique to determine the trust value is investigated under the condition that the confidence value is determined by each subsystem.

• Journal of the Institute of Electronics and Information Engineers
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• v.52 no.10
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• pp.56-63
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• 2015

Not only performance analysis but also power analysis at early design stages is important in designing a system-on-chip. We propose a power modeling based on clock gating enable signals that enables accurate power analysis at a high-level. Power state is defined as combinations of the values of the clock gating enable signals and we can extract the clock gating enable signals to generate the power model automatically. Experimental results show that the average power accuracy is about 96% and the speed gain of power analysis at the high-level power is about 280 times compared to that at the gate-level.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.10
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• pp.487-495
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• 2005

This paper reviews the characteristic of thermal and temperature of oil field cable in transient state such as grounding fault and lightning surge. For analysis in various conditions, many actual underground power cable systems are modeled using ATP. These results are applied for the examination of temperature increase when the single line to ground fault by the breakdown of insulation part and hitting of lightning surge are occurred. The inner part temperature of OF cable is analysed according to the various kinds of cable using the thermal model of transient state. The temperature increase of sheath and crossbonded lead bv fault current is also analysed using IEC 60949.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.4
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• pp.307-312
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• 2006

This paper proposes the SRM drive system, which accurately estimates the phase currents from the DC-link current to drive SRM instead of detecting the three-phase currents. In addition, the detecting circuit of DC-link current is also proposed to increase the resolution and decrease the off-set influence. Comparing with the general drive system based on the phase current, it is verified through the experiments that the proposed SRM drive system based on the DC-link current has the good performance in steady-state response of the speed control. Using the DC-link current, all of the 3-phase currents can be easily estimated for driving the SRM.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.54 no.8
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• pp.410-417
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• 2005

This paper analyses the transient phenomena against single line to ground fault and lightning surge on underground power cable systems. For analysis in various fault conditions, several actual underground power cable systems are modeled using ATP In ground fault, the transient characteristic of the conductor and the sheath according to the fault current and the installation types of CCPU are analysed. In lightning surge strokes, the various unbalanced conditions including the length of crossbonded lead, the breakdown of CCPU and distance unbalance are considered. This paper is expected to contribute the establishment of proper protection methods against transients on underground power cable systems.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.1
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• pp.8-15
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• 2015

This paper includes a method for estimating the parameter of a synchronous generator and exciter using the modified particle swarm optimization. A solid round rotor synchronous generator and exciter have been modeled with the saturation function. They are regarded as state of being cooperative to a infinite bus. The behavior characteristic of all particles assigned to a parameter needs to be reflected in the PSO algorithm to fine out more close result to the optimal solution. The results of the simulation to estimate the parameters of the synchronous generator and exciter in the modified PSO algorithm are described.

• Journal of Power Electronics
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• v.19 no.5
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• pp.1224-1234
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• 2019

Hybrid rotor position estimation methods that integrate a fundamental model and high frequency (HF) signal injection are widely used for the wide speed-range sensorless control of interior permanent-magnet synchronous machines (IPMSMs). However, the direct transition of two different schemes may lead to system fluctuations or system instability since two estimated rotor positions based on two different schemes are always unequal due to the effects of parameter variations, system delays and inverter nonlinearities. In order to avoid these problems, a seamless transition strategy to define and construct a virtual q-axis inductance is proposed in this paper. With the proposed seamless transition strategy, an estimated rotor position based on a fundamental model is forced to track that based on HF signal injection before the transition by adjusting the constructed virtual q-axis inductance. Meanwhile, considering that the virtual q-axis inductance changes with rotor position estimation errors, a new observer with a two-phase phase-locked loop (TP-PLL) is developed to accurately obtain the virtual q-axis inductance online. Furthermore, IPMSM sensorless control with maximum torque per ampere (MTPA) operations can be tracked automatically by selecting the proper virtual q-axis inductance. Finally, experimental results obtained from an IPMSM demonstrate the feasibility of the proposed seamless transition strategy.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.600-604
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• 2000

In this paper authors proposed a new nonlinear rotor flux observer for rotor field oriented control of an induction motor which is designed based on theory of the extended Luenberger observer(ELO) one of a nonlinear state observer. The proposed rotor flux observer is derived from the 2 phase model of induction motor by the theory of ELO. The simulation results taken under the varying condition of rotor resistance and load torque show fast convergence of estimated rotor flux and high performance of IM drive system is achieved 표 experiment.

• Journal of Industrial Technology
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• v.12
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• pp.61-67
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• 1992

Two control algorithms of active suspension system for improving ride quality are described and their effectiveness is assessed using a quarter car model. Optimal control approach demonstrates great flexibility to meet various running conditions of a vehicle. However, in order to fully utilize the power of optimal control apporach, accurate estimation of the state variables is essential. Simple, yet effective sky-hook algorithm seems to be well suited for real application because of its much relaxed requirements on sensing the stste variables and relative easiness to implment.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.10 no.2
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• pp.128-133
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• 2010

This paper presents a method for estimating the parameters of dynamic models for induction motor dominating loads. Using particle swarm optimization, the method finds the adequate set of parameters that best fit the sampling data from the measurement for a period of time, minimizing the error of the outputs, active and reactive power demands and satisfying the steady-state error criterion.