• Proceedings of the KIEE Conference
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• 1994.07a
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• pp.565-567
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• 1994

This paper presents a software based NPC PWM inverter control technique to eliminate the harmonics in the output waveforms of inverter. The proposed control technique is able to keep down total harmonic distortion and significantly improve the performance of the inverter. In the control node where the frequency ratio is 36 and the modulation index is $1.2\sim2.0$, the proposed inverter has been operated wi thin 5% Total Harmonic Distortion.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.8
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• pp.373-378
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• 2001

This paper introduces a new online index to quantify the harmonic distortion. The proposed index based on VI product can represent the harmonic distortion of both voltage and current, and it includes the effect of interharmonic distortion. Also, the new index is suitable to online harmonic distortion evaluation since it only requires the r.m.s. (root mean square) value and fundamental frequency value of the signals. Case studies are presented to show the availability of the proposed index using the comparison with the THD (Total Harmonic Distortion).

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.4
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• pp.473-479
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• 2008

With the advent of mobile phone, digital multimedia broadcasting(DMB) service is to be realized for multimedia data communication. For an acoustic part, a smaller and lighter microspeaker is also soon to be realized as an MP3 song player and a speakerphone. Sound quality in the microspeaker is becoming more important in mobile phones. It is evaluated by total harmonic distortion(THD). THD is the proportion of higher order frequencies output response to sinusoidal input signal. It is affected by uneven magnetic distribution and nonlinear response of diaphragm. In this paper, harmonic distortion is analyzed by considering magnetic and mechanical coupling effects. Simulated results of THD are compared with experimental data. Results show that THD in lower frequency range is higher due to high displace on voice coil and high mechanical response of high order frequency.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.236-241
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• 2008

With the advent of mobile phone, Digital multimedia broadcasting (DMB) service is to be realized for multimedia data communication. For an acoustic part, a smaller and lighter microspeaker is also soon to be realized as an MP3 song player and a speakerphone. Sound quality in the microspeaker is becoming more important in mobile phones. It is evaluated by total harmonic distortion (THD). THD is the proportion of higher order frequencies output response to sinusoidal input signal. It is affected by uneven magnetic distribution and nonlinear response of diaphragm. In this paper, harmonic distortion is analyzed by considering magnetic and mechanical coupling effects. Simulated results of THD are compared with experimental data. Results show that THD in lower frequency range is higher due to high displace on voice coil and high mechanical response of high order frequency.

• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.6-14
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• 2014

A new method to determine the total harmonic contributions of several customers and the utility at the point of common coupling is presented. The proposed method can quantify the individual harmonic impact of each suspicious harmonic source at the point of common coupling. The individual harmonic impact index is then used to assess the total harmonic contribution of each harmonic source. This index can be calculated by the results processed from instantaneous harmonic voltage and current phasor values. The results demonstrate the performance of the proposed method in terms of steady-state accuracy and response to time-varying operating conditions. The proposed index can be used for billing purposes to control harmonic distortion levels in power systems.

• Journal of Power Electronics
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• v.14 no.5
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• pp.890-898
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• 2014

Critical conduction mode boost power factor correction converters operating at the boundary of continuous conduction mode and discontinuous conduction mode have been widely used for power applications lower than 300W. This paper proposes an enhanced variable on-time control method for the critical conduction mode boost PFC converter to improve the total harmonic distortion characteristic. The inductor current, which varies according to the input voltage, is analyzed in detail and the optimal on-time is obtained to minimize the total harmonic distortion with a digital controller using a TMS320F28335. The switch on-time varies according to the input voltage based on the computed optimal on-time. The performance of the proposed control method is verified by a 100W PFC converter. It is shown that the optimized on-time reduces the total harmonic distortion about 52% (from 10.48% to 5.5%) at 220V when compared to the variable on-time control method.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.298-306
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• 2018

This paper presents a harmonic analysis of the modular multilevel converter (MMC) using a double Fourier series (DFS) algorithm. First, the application of DFS for harmonic calculation in the MMC is made by considering the effect of arm inductor. The analytical results are then confirmed by comparing with the simulation results of using the fast Fourier transform (FFT) algorithm. Finally, distribution of harmonics and total harmonic distortion (THD) in the MMC will be analyzed in three cases: harmonics versus number of levels of MMC, harmonics versus total switching frequency and harmonics versus modulation index. The simulation results are performed in the PSCAD/EMTDC simulation program in order to verify the analytical results obtained by Matlab programming.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1995.10a
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• pp.80-84
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• 1995

ABSTRACT - This paper presents a software based 3 phase 5 level pulse-width modulation(PWM) inverter to reduce total harmonic distortion. The proposed modulation technique can reduce total harmonic distortion and significantly improve the performance of the inverter. In the modulation mode where the frequency ratio is 36 and modulation index is 1.2∼2.0, harmonic components have been mostly eliminated and the magnitude of fundamental component have been maximized by the 3 phase 5 level PWM inverter.

• Proceedings of the KIEE Conference
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• 2000.07e
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• pp.74-78
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• 2000

In this paper a switching control circuit for shaping the line current and reducing the total harmonics distortion in the boost converter is presented. To solve the problems of performance degradation due to pulse waveform in the input current, the boost converter in which the harmonic distortion in the input current is reduced using a 3th harmonic-injected PWM is proposed. Finally, Simulation and experimental results of boost converter with 5[kHz] switching frequency are presented and correction of power factor and reduction of total harmonic distortion was established.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.3
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• pp.62-68
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• 2007

The increasing use of power electronic equipment in distribution system has been the reason for the greater concern about a harmonic in recent time. Therefore, it is necessary for measurement and modelling to analyze a harmonic level and a transfer characteristic in distribution system. In this paper, the Point of Common Coupling (PCC) is selected to analyze harmonic characteristic of distribution system by IEC 61000-3-6. Harmonic voltage and orient were measured at the PCC of real distribution system Harmonic distribution, nonlinear load component and Total Harmonic Distortion(THD) were verified. The effective and accurate modelling of real distribution system were proved through a analysis of harmonic impedance, voltage and current under steady-state. Harmonic transfer characteristic were investigated through a analysis of harmonic voltage and current under harmonic current source.