• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.4
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• pp.22-30
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• 2011

This study analyzes harmonic vibration with natural frequency according to the configuration of damper clutch. In the case of double spring, equivalent stress at same direction of the revolution at inner and outer coil spring is over 30% as compared with at its opposite direction. Natural frequency or harmonic response with maximum deformation in case of the less coil pitch is below 3Hz as compared with in case of the more coil pitch. As the coil pitch of damper spring as the case 2 or 4 becomes smaller, its mass and deformation can be large. In these cases, spring constant and natural frequency become smaller. In the case 5 or 6 of double spring at natural vibration or harmonic response, the frequency becomes over 300Hz. As the result of this study is applied by the design of damper spring, the damage at its connected part is prevented and the durability can be predicted.

• Journal of Power Electronics
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• v.10 no.4
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• pp.419-427
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• 2010

A parallel control strategy in capacity proportion frequency allocation mode for shunt active power filters (APFs) is proposed to overcome some of the difficulties in high power applications. To improve the compensation accuracy and overall system stability, an improved selective harmonic current control based on multiple synchronous rotating reference coordinates is presented in a single APF unit, which approximately implements zero steady-state error compensation. The combined decoupling strategy is proposed and theoretically analyzed to simplify selective harmonic current control. Improved selective harmonic current control forms the basis for multi-APF parallel operation. Therefore, a parallel control strategy is proposed to realize a proper optimization so that the APFs with a larger capacity compensate more harmonic current and the ones with a smaller capacity compensate less harmonic current, which is very practical for accurate harmonic current compensation and stable grid operation in high power applications. This is verified by experimental results. The total harmonic distortion (THD) is reduced from 29% to 2.7% for a typical uncontrolled rectifier load with a resistor and an inductor in a laboratory platform.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2119-2128
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• 2016

Due to detection and control errors, some high-frequency harmonics with voltage-source characteristics cause circulating currents in modular inverters. Moreover, the circulating currents are usually affected by the output filters (OF) of each module due to their filter and resonance properties. The interaction among the circulating currents in the modules increase the power loss and reduce system stability and control precision. Therefore, this paper reports the results of a study on the SPWM high-frequency harmonics circulating currents for a double-module VSI. In the paper, an analysis of the circulating-current circuits is briefly described. Next, a mathematic model of the single-module output voltage based on the carrier frequency of SPWM is built. On this basis, through mathematic modeling of high-frequency harmonic circulating currents, the formation mechanism and distribution characteristics of circular currents and their influences are studied in detail. Finally, the influences of the OF on the circulating currents are studied by mainly taking an LC-type filter as an example. A theoretical analysis and experimental results demonstrate some important characteristics. First, the carrier phase shifting of the SPWM for each module is the major cause of the SPWM harmonic circulating currents, and the circulating currents are in an odd distribution around n-times the carrier frequency $n{\omega}_s$, where n = 1, 2, 3, ${\ldots}$. Second, the harmonic circular currents do not flow into the parallel system. Third, the OF can effectively suppress the non-circulating part of the high-frequency harmonic currents but is ineffective for the circulation part, and actually reduces system stability.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.291-292
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• 2007

Porcelain insulators are widely used in overhead high-voltage power transmission lines while providing adequate insulation to withstand switching and lightning over voltages. For the safety consideration, we proposed a novel insulator inspection method using harmonic, which is retrieved from the low frequency signal. The working principle of this new method is based on the relationship between the low frequency harmonic and the defective characteristic of the insulators. So, in this paper, the harmonic retrieval in the complex noise is solved with the HOC (High Order Cumulants) is extended. In the experiment, as one of our dedicated contribution, we illustrate low frequency harmonic and the defective characteristics of the porcelain insulators.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2012.07a
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• pp.164-166
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• 2012

In this paper, we proposed a method for extracting predominant melody of polyphonic music based on harmonic structure. Harmonic structure is an important feature parameter of monophonic signal that has spectral peaks at the integer multiples of its fundamental frequency. We extract all fundamental frequency candidates contained in the polyphonic signal by verifying the required condition of harmonic structure. Then, we combine those harmonic peaks corresponding to each extracted fundamental frequency and assign a rank to each after calculating its harmonic average energy. We run pitch tracking based on the rank of extracted fundamental frequency and continuity of fundamental frequency, and determine the predominant melody. For the query by singing/humming (QbSH) task, we proposed Dynamic Time Warping (DTW) based matching engine. Our system reduces false alarm by combining the distances of multiple DTW processes. To improve the performance, we introduced the asymmetric sense, pitch level compensation, and distance intransitiveness to DTW algorithm.

• Journal of Electrical Engineering and Technology
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• v.6 no.3
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• pp.319-327
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• 2011

An iterative technique based on orthogonal filters and frequency tracking is proposed to estimate harmonic components in power systems. The technique uses frequency interpolation to estimate fundamental frequency and harmonics when the nominal frequency of the signal is a non-integer value. Due to the number of computations involved during the generation of filter coefficients, an offline computation is suggested. Beneficial features of the proposed technique include fixed sampling rate and fixed data window size. The performance of the proposed technique is examined by simulating different power system operating conditions and evaluating the data from these simulations. A technique based on Fast Fourier Transform is also used to estimate the harmonic components for all the simulated signals. These estimates are compared with those obtained from the proposed technique. Results show that the proposed technique can converge to the accurate fundamental frequency and therefore, provide accurate harmonic components even when the fundamental frequency is not equal to the nominal frequency.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.10
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• pp.233-239
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• 2012

The harmonic frequency occurred in a power system causes errors and failures of equipments such as motors, and an unnecessary power consumption. The fundamental countermeasure for the harmonic frequency is to eliminate the cause of the harmonic frequency. This paper describes about making the device to figure out the cause in real time, verifying the operation of the device, and utilizing it to various power quality measurements. The power usually has the line frequency between 45Hz and 66Hz. In this research, the number of the harmonic frequencies which can be analysed inside the 2.8kHz bandwidth, the filter bandwidth of ADE7880, is 2800/f, and the maximum is 2800/45 = 63. The maximum order of the harmonic frequency in Korea, which has the line frequency of 60Hz, was measured as 2800/60 = 46th. Also, the accuracy of the voltage, current, and power measurement had the error within 0.1%, confirming that it is very precise.

• Bulletin of the Korean Space Science Society
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• 2009.10a
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• pp.43.1-43.1
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• 2009

Electromagnetic radiation at the plasma frequency and its second harmonic, the so-called plasma emission, is fundamental process responsible for solar type II and III radio bursts. There have also been occasional observations of higher-harmonic plasma emissions in the solar-terrestrial environment. We will present that the simulation effort on characterizing the electron beam-generated plasma emission process at POSTECH. We have developed fully electromagnetic particle-in-cell (PIC) simulation code with three dimensions. We simulated harmonic plasma emission with various beam condition. Qualitative comparison with the traditional plasma frequency and second harmonic radiation theory is in good agreement. Higher harmonic emissions agree with the theory of coalescence of Langmuir and harmonic EM wave.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.3
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• pp.438-444
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• 2015

A new approach to the active phased arrays for the second harmonic generation is presented. Phase variation between the second harmonic oscillators by the mutual synchronization is analyzed theoretically. In this coupling, the active antenna consists of the FET oscillator which plays two roles in fundamental oscillation and frequency multiplying, and the patch antenna resonated at the second harmonic frequency. The radiated second harmonic wave was scanned by varying the free-running oscillation frequencies of the active antennas. In the experiment using the 2-elements array and the 4-elements array, the radiated beam of the second harmonic wave was scanned more widely compared with the case of the fundamental wave radiation.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.5
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• pp.459-464
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• 2013

A reset-free anti-harmonic programmable multiplying delay-locked loop (MDLL) that provides flexible integer clock multiplication for high performance clocking applications is presented. The proposed MDLL removes harmonic locking problems by utilizing a simple harmonic lock detector and control logic, which allows this MDLL to change the input clock frequency and multiplication factor during operation without the use of start-up circuitry and external reset. A programmable voltage controlled delay line (VCDL) is utilized to achieve a wide operating frequency range from 80 MHz to 1.2 GHz with a multiplication factor of 4, 5, 8, 10, 16 and 20. This MDLL achieves a measured peak-to-peak jitter of 20 ps at 1.2 GHz.