• The Transactions of the Korean Institute of Power Electronics
• /
• v.4 no.1
• /
• pp.82-90
• /
• 1999

A pulse frequency control method for single-switch three-phase buck rectifiers is comprehensively studied in this paper. The proposed pulse frequency control method leads the three-phase buck rectifier to a high performance system that can draw the nearly sinusoidal input-line currents. The simulated and experimental results demonstrate that the system provides low total harmonic distortion of the input-line currents, high-power factor, and good output voltage regulation against load change.

• Proceedings of the KIPE Conference
• /
• 2007.11a
• /
• pp.11-14
• /
• 2007

In recent years, installation of the new and renewable energy system is rapidly increasing. Because the new and renewable energy system is a practical distributed generation system to save energy resources and to keep environments clean. Conventional single-phase utility interactive inverter controls output current by using PI current controller. However, this method is insufficient to suppress harmonic current resulted from nonlinear loads in grid line. In this paper, in order to suppress periodic waveform distortion and improve THD(Total Harmonic Distortion), new type current controller added a parallel repetitive controller is proposed and then performance of the proposed controller was verified with computer simulation.

• Journal of Power Electronics
• /
• v.16 no.4
• /
• pp.1407-1414
• /
• 2016

Unlike existing pulse-width modulation (PWM) techniques, such as sinusoidal PWM and random PWM, the wavelet PWM (WPWM) technique based on a Harr wavelet function can achieve a high fundamental component for the output voltage, low total harmonic distortion, and simple digital implementation. However, the original WPWM method lacks output voltage control. Thus, the practical application of the WPWM technique is limited. This study proposes an improved WPWM technique that can regulate output voltage amplitude with the addition of a parameter. The relationship between the additional parameter and the output voltage amplitude is analyzed in detail. Experimental results verify that the improved WPWM exhibits output voltage control in addition to all the merits of the WPWM technique.

• Journal of Electrical Engineering and Technology
• /
• v.8 no.6
• /
• pp.1345-1351
• /
• 2013

Variable iron loss as function of current phase angle of Interior Permanent Magnet Synchronous Motor(IPMSM) was calculated through Curve Fitting Method(CFM). Also, a magnetic flux density distribution of iron core according to current phase angle was analyzed, and an iron loss calculation was performed including harmonic distortion. The experiment was performed by production of non-magnetizing model for the separation of mechanical loss, and the iron loss was calculated by the measurement of input using power analyzer and output power using dynamometer. Some error was generated between experimental results and calculation value, but an iron loss diminution according to current phase angle followed a same pattern. So, errors were generated by measurement, vibration, noise, harmonic distortion loss, etc.

• Proceedings of the KIPE Conference
• /
• 2003.11a
• /
• pp.90-94
• /
• 2003

Recently, many nations have released standard such as IEC 1000-3-2 and IEEE 519 which impose a limit on the harmonic current drawn by equipment connected to AC line in order to prevent the distortion of an AC line. Among the wide variety of active methods for improving power factor and harmonic distortion, the boost converter is very effective because it has a continuous line current , small choke filter and high power factor. In high power application, however, the bridge diode loss in the boost converter has made the efficiency lower and the temperature of the board higher. A new approach without bridge diode to make the same characteristics of the conventional boost converter has also been developed. This paper present the comparisons between the continuous current mode(CCM) operated conventional boost converter and the boundary current mode(BCM) operated the bridgeless boost converter for high efficiency and high power factor.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.51 no.3
• /
• pp.125-132
• /
• 2002

This paper presents a single-phase 3-level PWM inverter to alleviate the harmonic components of output voltage and current under the conditions of identical supply DC voltage and switching frequency to the conventional inverter. Operational principles and analysis are performed, and the switching functions are derived. Deadbeat controller is also designed and implemented for the inverter to keep the output voltage being sinusoidal and to have the high dynamic performances even in the cases of load variations and the partial magnetization of filter inductor. The validity of proposed inverter is proved from the simulated and experimented results.

• Journal of international Conference on Electrical Machines and Systems
• /
• v.1 no.3
• /
• pp.366-371
• /
• 2012

In this paper, we propose an electric circuit using one common-arm of H-Bridge inverters to reduce the number of switching components in the multi-level inverter combined with H-Bridge inverters and transformers. And furthermore, we suggested a new multi-level PWM inverter using PWM level to reduce THD (Total Harmonic Distortion). We use a phase-shift switching method that has the same rate of usage at each transformer. Also, we test the proposed prototype 9-level inverter to clarify the proposed electric circuit and reasonableness of the control signal for the proposed multi-level PWM inverter.

• Journal of Electrical Engineering and Technology
• /
• v.7 no.1
• /
• pp.69-74
• /
• 2012

This paper presents a distributed winding type axial flux permanent magnet synchronous generator (AFPMSG) with reduced the total harmonic distortion (THD), suitable for wind turbine generation systems. Although the THD of the proposed distributed winding type is more reduced than the concentrated winding type, the unbalance of the phase back EMF occurs. To improve the unbalance of the phase back EMF and the output power of the distributed winding type AFPMSG, the Kriging based on the latin hypercube sampling (LHS) is utilized. Finally, these optimization results are confirmed by experimental results. As a result, the unbalance of the phase back EMF and the output power of the distributed winding type AFPMSG were improved while maintaining the total harmonic distortion (THD) and the average phase back EMF.

• Journal of Power Electronics
• /
• v.16 no.3
• /
• pp.994-1003
• /
• 2016

Two major obstacles in the utilization of electrical vehicles are their price and range. The collaboration of direct torque control (DTC) with induction motor (IM) is preferred for its low cost, easy implementation, and parameter independency. However, in terms of edges, the method has drawbacks, such as variable switching frequency and undesired current harmonic distortion. These drawbacks result in acoustic noise, reduced efficiency, and electromagnetic interference. A feed-forward approach for stator-flux-oriented DTC with space vector pulse-width modulation is presented in in this paper. The outcome of the proposed method is low current harmonic distortion with fixed switching frequency while preserving the torque performance and simple application feature of basic DTC. The method is applicable to existing and forthcoming IM drive systems via software adaptation. The validity of the proposed method is confirmed by simulation and experimental results.

• The Transactions of the Korean Institute of Electrical Engineers A
• /
• v.49 no.2
• /
• pp.50-55
• /
• 2000

This paper presents the feature extraction of fault currents related to the multi-shot reclosing scheme in the power distribution system. In order to get the fault current waveform, we have measured the fault currents by the fault recorders which have been installed at the secondary side of 154/22.9[kV] substation transformer. These waveforms are classified into temporary and permanent fault. For the classified waveforms, Fourier transform is used to extract the feature of the fault current waveforms. After the waveforms are analyzed by using Fourier transform, the magnitude spectrum and the relative variation of THD (Total Harmonic Distortion) are calculated. And then the relative variation of THD is great in the temporary faults, and is small in the permanent faults.