• Journal of the Korea Society of Computer and Information
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• v.29 no.6
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• pp.143-151
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• 2024

In this paper, the inductor current distortion in a boost PFC (Power Factor Correction) converter under light load is mathematically analyzed, and its reasons are defined. In the average current mode control under light load, the inductor current is discontinuous, resulting in an inaccurate inductor current average value being reflected in the current control. In predictive current mode control, the current ripple is relatively large compared to the inductor current, leading to severe current distortion. In addition, the switch is turned off near the peak of the inductor current when model predictive current control is applied. Inductor current distortion must be addressed because it leads to an increase in total harmonic distortion and a decrease in power factor. In this paper, the design procedure to mitigate the light load current distortion in boost PFC converter is selected based on the mathematical analysis. Finally, a comparative analysis of control methods under light load is performed using hardware-in-the-loop simulation.

• Transactions of the Korean Society of Automotive Engineers
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• v.23 no.2
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• pp.239-245
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• 2015

In order to control the hybrid power system efficiently, the knowledge for the required load of the system is important. The agricultural tractor performs various farm works such as plow, rotary, and baler. When it performs rotary tillage and baler operation, the generated work load is analyzed. To analyze trend of work load, moving average technique is applied to the measurement data. Optimal control inputs for the two works are obtained from simulation using the dynamic programming. The novel fundamental control strategy for parallel hybrid tractor called Max. SOC is proposed.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.8
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• pp.109-117
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• 2004

A study on gust load alleviation using aircraft control surface was performed. Aeroservoelastic model including control surface controller was formulated and validated by comparing the results of continuous gust response analysis with those of MSC/NASTRAN. Optimal control with output feedback was adopted for designing the control surface controller, and the effects of gust load alleviation was validated by performing the numerical simulation for the controller designed.

• Journal of Power System Engineering
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• v.18 no.5
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• pp.150-155
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• 2014

This paper presents The performance analysis of inverter control type-industrial cooler with respect to refrigeration load and outdoor temperature. Aside from materials about simulations and foundation data regarding inverter control compressors, currently, data about commercial coolers with inverter control still lack information for performance comparison. Thus, in this paper, the experiments are done to see characteristics of condensation capacity, evaporation capacity, compressor power and COP with respect to outdoor temperature and load by using a commercial inverter control cooler model. As a result, COP difference of the inverter control cooler with respect to load is 30% at the outdoor temperature of $35^{\circ}C$, 29% at the outdoor temperature of $30^{\circ}C$, 34% at $25^{\circ}C$, respectively.

• KIEAE Journal
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• v.16 no.6
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• pp.13-19
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• 2016

Purpose: In this study, we examined outdoor air fraction using historical data of actual Air Handling Unit (AHU) in the existing building during intermediate season and analyzed optimal outdoor air fraction by control types for economizer. Method: Control types for economizer which was used in analysis are No Economizer(NE), Differential Dry-bulb Temperature(DT), Diffrential Enthalpy(DE), Differential Dry-bulb Temperature+Differential Enthalpy(DTDE), and Differential Enthalpy+Differential Dry-bulb Temperature (DEDT). In addition, the system heating and cooling load were analyzed by calculating the outdoor air fraction through existing AHU operating method and control types for economizer. Result: Optimized outdoor air fraction through control types was the lowest in March and distribution over 50% was shown in May. In case of DE control type, outdoor air fraction was the highest of other control types and the value was average 63% in May. System heating load was shown the lowest value in NE, however, system cooling load was shown 1.7 times higher than DT control type and 5 times higher than DE control type. For system heating load, DT and DTDE is similar during intermediate season. However, system cooling load was shown 3 times higher than DE and DEDT. Accordingly, it was found as the method to save cooling energy most efficiently with DE control considering enthalpy of outdoor air and return air in intermediate season.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.6
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• pp.535-542
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• 2006

A large signal stability analysis of the solar array regulator system is performed to facilitate the design and analysis of a Low-Earth-Orbit satellite power system. The effective load characteristics of every controllable method in the solar array system are classified to analyze the large signal stability. Then, using the state plane analysis technique, the stability of various equilibrium points is analyzed. A nonlinear transformation algorithm, which changes the effective load characteristic of the solar array regulator as constant resistive load, is also proposed for the large signal stability. The proposed resistive current mode control system can control the solar array output for purposes such as peak power tracking control and battery charging control. For the verification of the proposed large signal analysis and resistive current mode control, a solar array regulator system consisting of two 100W parallel module buck converters has been built and tested using a real 200W solar array.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.249-258
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• 1999

Dynamic load and static load tests are performed on steel pipe piles and concrete piles at five construction sites in highway to compare the difference of load bearing mechanisms. At each site, one steel pile is instrumented with electric strain gages and dynamic tests are performed on the pile during installation. Damages of strain gages due to the installation are checked and static test is performed upon the same pile after two or seven days as well. It shows that load transfer from side friction to base resistance behaves somewhat differently according to the results of load-settlement analysis obtained from PDA and static load test. Initial elastic stage of load settlement curves of two load tests is almost similar. But after the yielding point, dynamic resistance of pile behaves more stiffer than static resistance, thus, dynamic load test result might overestimate the real pile capacity compared with static result. Analysis of gage readings shows that unit skin friction increases exponentially with depth. The skin friction is mobilized at the 1∼2m above the pile tip and contributes to the considerable side resistance. Comparison of side and base resistances between the measured value and the calculated value by Meyerhof's bearing capacity equation using SPT N value shows that the calculated base resistance is higher than the measured. Therefore, contribution of side resistance to total capacity shouldn't be ignored or underestimated. Finally, based upon the overall test results, a construction control procedure is suggested.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.3
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• pp.87-92
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• 2011

This study analyzes structural stress and fatigue on control arm of automobile under nonuniform load. Maximum equivalent stress at bolt part is shown with 419.1MPa and the corner is deformed with maximum displacement of 1.1628mm. Among 3 cases of nonuniform fatigue loads applying on control arm, 'SAE bracket history' with the severest change of load becomes most unstable but 'Sample history' becomes most stable. In case of 'Sample history' with the average stress of $-10^5MPa$ to $10^5MPa$ and the amplitude stress of 0 MPa to $10^5MPa$, the possibility of maximum damage becomes 3%. This stress state can be shown with 6 times more than the damage possibility of 'SAE bracket history' or 'SAE transmission'. Safety and durability on automobile can be effectively improved by applying the fatigue analysis result on control arm.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.7
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• pp.256-262
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• 2016

This study performed the back-pressure cold forging analysis to minimize the non-forming area of gear teeth for the output hub and reaction hub in automatic transmission. Two important factors of the back-pressure cold forging process, the load of the punch and the backup force applied to the sleeve, were determined through displacement control analysis. The non-forming area of the gear teeth was compared with both cases of the displacement control analysis and load control analysis, and their solution is similar to the measuring result of a real workpiece. The results show that the load of the punch is dependent on the reduction area of the workpiece, and the backup force applied to the sleeve is determined with regard to the cross-section-area of sleeve. This analysis procedure can be useful and effective in determining the manufacturing condition of the back-pressure cold forging process to minimize the non-forming area.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1079-1080
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• 2006

This paper presents the methods to save energy by using load consumption pattern analysis. Base on the substation annual power usage data, the characteristic of the substation power consumption have investigated. With this investigation effective electrical billing condition and the control target load has been determined. Most of power usage comes from the motor car, so power system and load table of motor car were reviewed. And in the metropolitan area the peak power consumption occurs at summer or winter rush hours because of its typical characteristics. From this data control point of time are determined. Through the whole study the methode to control the power Peak consumption are proposed and prototype was designed.