• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.621-624
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• 2005

Among many auditory feelings for the vehicle interior noise, booming is considered as the most important nuisance to the passenger and developer. Because the main source of booming noise is a power train system including engine, in general, it consists of tonal components related to fundamental engine rotation and its harmonics including the firing frequency. Therefore, it is demanded to extract the effective tonal components only by using pitch extraction algorithm based on the place theory enable to find aurally relevant tonal components. However, there is a difference between booming sensation and pitch perception according to frequency change of tonal component. In this study, subjective listening test using a tracking method was performed to find the difference limen for just noticeable change of booming sensation in frequency. 20 Koreans and 10 Japanese were participated in this test and the results obtained from Koreans and Japanese were compared with each other. Finally, 5Hz was determined as the difference limen for just noticeable change of booming sensation in frequency, and by applying this value to booming analysis using pitch concept, it was confirmed that the degree of prediction of booming sensation was improved.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.23 no.1
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• pp.49-58
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• 2009

This paper presents the vector control of single phase induction motor(SPIM) to operate water pumping system using PV system with a maximum power point tracking(MPPT). The water pumping system uses a variable speed SPIM driven a centrifugal pump by field oriented control(FOC) inverter. The MPPT using a DC-DC converter controlled the duty cycle to track maximum power from PV under different insolation conditions. The duty cycle directly relate with a flux producing current control($i_{ds}$). The FOC inverter uses a current control voltage source inverter(CC-VSI). The simulation results are shown that the characteristics and performance of drive system, which varies as each conditions of light by expresses in voltage($V_{dq}$), current($I_{dq}$), speed of motor and torque.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.3
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• pp.238-248
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• 2016

In this study, an automatic command mode transition strategy of direct power control (DPC) is proposed for permanent magnet synchronous generators (PMSGs) medium-voltage (MV) offshore wind turbines (WTs). Benchmarking against the control methods are performed based on a three-level neutral-point-clamped (NPC) back-to-back type voltage source converter (VSC). The ramping rate criterion of complex power is utilized to select the switching vector in DPC for a three-level NPC converter. With a grid command and an MPPT mode transition strategy, the proposed control method automatically controls the generated output power to satisfy a grid requirement from the hierarchical wind farm controller. The automatic command mode transition strategy of DPC is confirmed through PLECS simulations based on Matlab. The simulation result of the automatic mode transition strategy shows that the proposed control method of VOC and DPC achieves a much shorter transient time of generated output power than the conventional control methods of MPPT and VOC under a step response. The proposed control method helps provide a good dynamic performance for PMSGs MV offshore WTs, thereby generating high quality output power.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1064_1065
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• 2009

PV (Photovoltaic) power generation system has been widely studied as a clean and renewable power source. Tracking the MPP (maximum power point) of a PV array is usually an essential part of a PV system. This paper describes POS (Photovoltaic Output Sensorless) MPPT method and optimization technique of its operational characteristics for grid-connected PV generation system. A DC-DC converter has been used to step-up the PV voltage and DC-AC converter has been used for connecting the system to the grid. Optimization technique has been implemented to optimize the current and voltage controller gain parameters and duty ratio increment of DC-DC converter. Simulation results reveal that the proposed control has better response.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.109.2-109.2
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• 2011

A photovoltaic system is getting the spotlight for a environment-friendly energy source. But its location is limited because a lot of land is necessary for photovoltaic arrays. Nevertheless, its dissemination is rapidly increasing more than 40 % every year and exceeded about 400 MW in 2009. The radical growth of a photovoltaic system aggravated a lack of sites, so that forests and farmland were destroyed. It is demanded to make use of a vacant lot or little piece of land for the way to solve the lack of sites and improve the location requirements for a photovoltaic system. General photovoltaic arrays are consist of a single layer structure and needs enough separation distances to maximize the amount of solar radiation and to eliminate influences by the shadow of other arrays. So that a large amount of land is required for the site. The solar cell arrays with long separation distances can not be placed in a small vacant lot and its site application efficiency is low. This study optimized photovoltaic arrays as multilayered structure with movable sleeves for the efficient photovoltaic in a small site. The existing photovoltaic arrays with a single layer structure were fixed or tracking systems. In this experimental equipment, photovoltaic arrays attached to the multilayers have rectilinear movement and rotary motion using sleeves. Therefore, shadow influences were removed and the generation capacity was improved. On the simulation result, generation increased by about 30% in the same site considering shadow influences and so on.

• Environmental Engineering Research
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• v.17 no.3
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• pp.167-174
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• 2012

In situ particle size spectra are obtained from two sequent cruises in order to evaluate the physical consequences of suspended particulate matters caused by episodic storm runoff from the Santa Ana River watershed, an urbanized coastal watershed. Suspended particles from various sources including surface runoff, near-bed resuspension, and phytoplankton are identified in empirical orthogonal function (EOF) analysis and an entropy-based parameterization (Shannon entropy). The first EOF mode is associated with high turbidity and fine particles as indicated by the elevated beam attenuation near the Santa Ana River and Newport Bay outlets, and the second EOF mode explains the suspended sediment dispersal and particle coarsening at the near-surface plume. Chlorophyll particles are also distinguished by negative magnitudes of the first EOF mode, which is supported by the relationship between fluorescence and beam attenuation. The integrated observation between the first EOF mode and the Shannon entropy index accentuates the characteristics of two different structures and/or sources of sediment particles; the near-surface plumes are originated from runoff water outflow, while the near-bottom particles are resuspended due to increased wave heights or mobilizing bottom turbidity currents. In a coastal pollution context, these methods may offer useful means of characterizing particle-associated pollutants for purposes of source tracking and environmental interpretation.

• The Journal of the Acoustical Society of Korea
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• v.21 no.2E
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• pp.71-80
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• 2002

This paper suggests the Cardioid beamforming algorithm of the doublet sensors employing DIFAR (directional frequency analysis and recording) sensor signals in the frequency domain. The algorithm enables target bearing estimation using the signals from directional sensors. The algorithm verifies its applicability by successfully estimating bearings of a target projecting ten narrow-band signals in shallow water. The estimated bearings agree very well with those from GPS (global positioning system) data. Assuming the bearings from GPS data to be real values, the estimation errors are analyzed statistically. The histogram of estimation errors in each frequency have Gaussian shape, the mean and standard deviation dropping in the ranges -1.1°∼ 6.7°and 13.3∼43.6°, respectively. Estimation errors are caused by SNR (signal to noise ratio) degradation due to propagation loss between the source and receiver, daily fluctuating geo-magnetic fields, and non-stationary background noises. If multiple DIFAR systems are employed, in addition to bearing, range information could be estimated and finally localization or tracking of a target is possible.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1771-1774
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• 2005

Recently, RFID has become popular in the field of remote sensing applications. Location awareness is one of the most important keys to deploying RFID for advanced object tracking. Generally, multiple reference RF stations or additional sensors are used for the location sensing with RFID, but, particularly in indoor environments, spatial layout and cost problems limit the applicability of those approaches. In this paper, we propose a novel method for location sensing with active RFID systems not requiring the need for reference stations or additional sensors. The system triangulates the position of RF signal source using the signal pattern of the loop antenna connected to the power detector. The power detector consists of a signal strength detector and a signal analysis unit. The signal analysis unit indicates the signal strength and serial number using the signal from the strength detector, and provides the direction of the signal to the application target. We designed three different signal analysis units depending on the threshold type. The developed system can sense the direction to the transponder located over 10 m away within the maximum error of $5^{\circ}$. It falls within a reasonable range in our normal office environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12B
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• pp.2275-2282
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• 1999

In ATM networks, bandwidth allocation using available bandwidth is important to control ABR traffic efficiently. However, it is difficult to dynamically assign bandwidth on bursty traffic, because the tracking of the existing available bandwidth information uses statistical value. In this paper, we propose a output-bufferd ATM switch using Per-VC queueing scheme with timer and Controller. The controller determines whether each VC is in congestion state or not, and the timer can assign dynamically as determining the available bandwidth for the Present period by Backlogged time and total link capacity, and then transmitting the determined bandwidth to source. Instead of using statistical parameters, the proposed scheme can improve link efficiency as allocating the bandwidth of the next period, by use of measured bandwidth during the current period.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.3
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• pp.241-247
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• 2005

This paper deals with the operation of a flywheel energy storage UPS. The UPS has good features such as long life-time, improved efficiency, no environmental problems, reduced size and space, and low maintenance cost compared with the conventional UPS using battery. The operating principle of the UPS is analysed in each mode including voltage compensation as well as uninterruptible power supply. Especially, the tracking characteristic of the disturbed phase of the source voltage after outage is analysed. The usefulness of the system is proved through simulations and experiments.