• 제어로봇시스템학회:학술대회논문집
• /
• 1990.10a
• /
• pp.663-668
• /
• 1990

This paper deals with the application of a Generalized Predictive Control (CPC) to a Pressurized Water Reactor (P.W.R) Nuclear Power Plant. Generalized Predictive Control is a sort of Explicit Self-Tuning Control. Current self-tuning algorithms lack robustness to prior choices of either dead-time (input time delay of a plant) or model order. GPC is shown by simulation studies to be superior to accepted self-tuning techniques such as minimum variance and pole-placement from the viewpoint that it is robust to prior choices of dead-time or model order. In this paper a GPC controller is designed to control the P.W.R. nuclear power rlant with varying dead-time and through the designing procedure the designer is free from the constraint of knowing the exact dead-time. The controller is constructed based on the 2nd order linear model approximated in the vicinity of operating point. To ensure that this low-order model describes the complex real dynamics well enough for control purposes, model parameters are updated on-line with a Recursive Least Squares algorithm. Simulation results are successful and show the possibilities of the GPC control application to actual plants with varying or unknown dead-time.

• Nuclear Engineering and Technology
• /
• v.47 no.3
• /
• pp.332-339
• /
• 2015

The leak before break (LBB) concept is widely used in designing pipe lines in nuclear power plants. According to the concept, the amount of leaking liquid from a pipe should be more than the minimum detectable leak rate of a leak detection system before catastrophic failure occurs. Therefore, accurate estimation of the leak rate is important to evaluate the validity of the LBB concept in pipe line design. In this paper, a program was developed to estimate the leak rate through circumferential cracks in pipes in nuclear power plants using the Henry-Fauske flow model and modified Henry-Fauske flow model. By using the developed program, the leak rate was calculated for a circumferential crack in a sample pipe, and the effect of the flow model on the leak rate was examined. Treating the crack morphology parameters as random variables, the statistical behavior of the leak rate was also examined. As a result, it was found that the crack morphology parameters have a strong effect on the leak rate and the statistical behavior of the leak rate can be simulated using normally distributed crack morphology parameters.

• Journal of Electrical Engineering and Technology
• /
• v.12 no.3
• /
• pp.1156-1165
• /
• 2017

A high performance interleaved bridgeless boost power factor correction (PFC) rectifier operating under the critical current conduction mode (CrM) is proposed in this paper to improve the efficiency and system performance of various applications, such as nano-grid systems. By combining the interleaved technique with the bridgeless topology, the circuit contains two independent branches without rectifier diodes. The branches operate in interleaved mode for each respective half-line period. Moreover, when operating in CrM, all the power switches take on soft-switching, thereby reducing switching losses and raising system efficiency. In addition, the input current flows through a minimum amount of power devices. By employing a commercial PFC controller, an effective control scheme is used for the proposed circuit. The operating principle of the proposed circuit is presented, and the design considerations are also demonstrated. Simulations and experiments have been carried out to evaluate theoretical analysis and feasibility of the proposed circuit.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.33 no.6A
• /
• pp.635-642
• /
• 2008

We propose the Optimum Power Allocation (OPA) scheme for Distributed Antenna Systems(DAS) in the time-varying Rayleigh fading channel. Recently, the OPA schemes which uses the Channel State Information (CSI) including a small scale (fast) fading have been proposed. However, the channel is changing vary fast over time due to small scale fading, therefore Bit Error Rate (BER) increases. Because of this reason, we derive the OPA for minimizing BER in DAS, which only uses a large scale fading to CSI and excepts a small scale fading. The simulation results show that the proposed OPA achieves better BER performance than conventional OPA considering a small scale fading in time-varying Rayleigh fading channel, and also has similar performance in Rayleigh flat-fading environment. The BER performance of proposed OPA which derived in Rayleigh fading channel is similar to minimum BER of Ricean fading channel which has small Line-of-Sight (LOS).

• The Journal of the Acoustical Society of Korea
• /
• v.33 no.4
• /
• pp.262-267
• /
• 2014

Recently, long pulses are transmitted for target detection in active sonar application. Matched filtering implemented by simple convolution algorithm, requires massive computational power for long replica. The computational loads are reduced significantly by implementing the convolution in the frequency domain with overlap add method, but the performance degrades for specified input/output system delay which constrains the size of FFT function. For performance improvement, the replica could be partitioned into uniform blocks (FDL) by re-using IFFT operations, or variable blocks of increasing length (MC) by using the largest possible blocks to calculate the convolution. In this paper, by combining the strong points of the two methods, we propose a new filter partition structure that allows for further optimization of the previous two methods.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.11 no.6
• /
• pp.38-43
• /
• 1974

A design problem is studied for a nonuniform transmission line (NUTL) section to be inserted between an arbitrary source impedance and an arbitary load impedance for the purpose of impedance matching or providing a minimum input reflection coefficient over a frequency ranee as wide as possible. A special class of NUTL's, yet comprehensive enough to include almost all smoothly varying lines, are considered. Power series expansions of the ABCD parameters of such lines are used in the calculation of the input reflection coefficient. The design problem is formulated as a nonlinear programming problem withnonlinear constraints and is solved by a combined use of the sequential unconstrained minimization technique and tile Fletcher-Powell method. As a result, a line section was obtained which shows a marked improvement over any one hitherto published as a wide-band impedance matching device.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1996.05b
• /
• pp.622-627
• /
• 1996

Detailed analysis of Feedwater Line Break (FLB) event for the fuel failure point of view are lack because the event was characterized as the increase in reactor coolant system (RCS) pressure. Up to now, the potential of the rapid system heatup case has been emphasized and comprehensively studied. The cooldown effects of FLB event is considered to be bounded by the Steam Line Break (SLB) event since the cooldown effect of SLB event is larger than that of the FLB event. This analysis provides a new possible path which can cause the fuel failure. The new path means that the fuel failure can occur under the heatup scenario because the Pressurizer Safety Valves (PSVs) open before the reactor trips. The 1000 MWe typical C-E plant FLB event assuming Loss of Offsite Power (LOOP) at the turbine trip has been analyzed as an example and the results show less than 1% of the fuel failure. The result is well within the acceptance criteria. In addition to that, a study was accomplished to prevent the fuel failure for the heatup scenario case as an example. It is found that giving the proper pressure gap between High Pressurizer Pressure Trip (HPPT) analysis setpoint and the minimum PSV opening pressure could prevent the fuel failure.

• Journal of Information Processing Systems
• /
• v.15 no.2
• /
• pp.331-343
• /
• 2019

Dynamic thermal rating of the overhead transmission lines is affected by many uncertain factors. The ambient temperature, wind speed and wind direction are the main sources of uncertainty. Measurement uncertainty is an important parameter to evaluate the reliability of measurement results. This paper presents the uncertainty analysis based on Monte Carlo. On the basis of establishing the mathematical model and setting the probability density function of the input parameter value, the probability density function of the output value is determined by probability distribution random sampling. Through the calculation and analysis of the transient thermal balance equation and the steady- state thermal balance equation, the steady-state current carrying capacity, the transient current carrying capacity, the standard uncertainty and the probability distribution of the minimum and maximum values of the conductor under 95% confidence interval are obtained. The simulation results indicate that Monte Carlo method can decrease the computational complexity, speed up the calculation, and increase the validity and reliability of the uncertainty evaluation.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
• /
• v.19 no.1
• /
• pp.15-22
• /
• 2008

In this paper, we propose a numerical analysis on reversed current of distributed amplifier based on transmission line theory and proposed a theory to obtain optimum transmission line length to minimize the reversed currents by cancelling those components. The reversed current is analyzed as being simply absorbed into the terminal resistance in the conventional analysis. In the proposed analysis, however, they are designed to be cancelled by each other with opposite phase by the optimal length of the transmission lint Circuit simulation and implementation using pHEMT transistor were performed to validate the proposed theory with the cutoff frequency of 3.6 GHz. From the measurement, maximum gain of 14.5dB and minimum gain of 12.3dB were achieved In the operation band. Moreover, measured efficiency of the proposed distributed amplifier is 25.6% at 3 GHz, which is 7.6%, higher than the conventional distributed amplifier. Measured output power Is about 10.9dBm, achieving 1.7dB higher output power than the conventional one. Those improvement is thought to be based on the cancellation of refersed current.

• Journal of the korean Society of Automotive Engineers
• /
• v.15 no.3
• /
• pp.36-46
• /
• 1993

In CVT vehicle, the engine speed is completely decoupled from the vehicle speed within the range from maximum transmission ratio to minimum transmission ratio. This allows the engine to operate in optimal state(e.g. best fuel economy or maximum power mode.) In this study, the CVT control algorithm for optimal operation of engine is suggested. In order to implement the real time digital control of electro-hydraulic CVT system, a software called CVTCON has been developed. CVTCON also includes the CVT operation module, (2) system test module, (3) system control module and (4) data management module. By using the CVTCON and the electro-hydraulic CVT system, two modes of experiments were carried out: constant throttle opening mode and acceleration mode. From the experimental result, it was found that the algorithm suggested in this study showed optimal operation of the CVT system.