• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.187-189
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• 2003

Conventional Switched Mode Power Supplies(SMPS) with diode-capacitor rectifier have distorted input current waveform with high harmonic content. Typically, these SMPS have a power factor lower than 0,65. To improve with this problem the power factor correction(PFC) circuit of power supplies has to be introduced. Specially. to the reduce size and manufacture cost of power conversion device, the single-stage PFC converter is increased to demand as necessary of study. in this paper, The comparative analysis of power factor correction circuit using Feedforward control with average current mode flyback converter(single-stage) and boost converter(two-stage). Also, the validity of designed and manufactured high power factor flyback converter and boost converter is confirmed by simulation and experimental results.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1244-1246
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• 2003

Conventional Switched Mode Power Supplies(SMPS) with diode-capacitor rectifier have distorted input current waveform with high harmonic content. Typically, these SMPS have a power factor lower than 0.65. To improve with this problem. the power factor correction(PFC) circuit of power supplies has to be introduced. Specially, to reduce size and manufacture cost of power conversion device, the single-stage PFC converter is increased to demand as necessary of study. In this case single-stage PFC converter has been used DC-DC converter with boost converter. However in this paper, it is studied flyback converter of high power factor, high efficiency by feedforward control. Also, the validity of designed and manufactured high power factor flyback converter is confirmed by simulation and experimental results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.8 s.99
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• pp.825-834
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• 2005

In this paper, a new signal canceller that input signals are equally group-delayed and cancelled each other is proposed and feedforward linearizing power amplifier that adopt the proposed signal cancellers is fabricated. Although the conventional signal canceller can't matches the phase and the group delay time of input signals simultaneously, the proposed signal canceller matches those simultaneously. Simultaneous matching of the phase and the group delay time can makes wideband signal cancellation. The main signal cancellation loop of the fabricated feedforward amplifier with the proposed signal cancellers cancel input signal more than 26.3 dB and the intermodulation distortion signal cancellation loop cancel more than 15.2 dB for 200 MHz bandwidth. And the proposed feedforward power amplifier improves C/I ratio by 20.8 dB with two tones at 2,115 MHz, 2,165 MHz, respectively.

• Journal of Power Electronics
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• v.15 no.3
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• pp.577-586
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• 2015

The combination of voltage feedforward and feedback control is a conventional approach for correcting the power factor in single-phase ac-dc boost converters. The feedback duty ratio increases significantly with an increase of the line frequency and input inductance. Therefore, the performance of the conventional approach is highly dependent on the bandwidth of the feedback controller. As a result, the input power quality can be significantly exacerbated due to uncompensated duty ratios if the feedback controller is limited. This paper proposes an input impedance and current feedforward control method to reduce the control portion of the feedback controller. The findings in this paper are 1) the theoretical derivation and analysis of variations of line frequency and input inductance on a power factor correction approach, 2) guaranteed consistent performance in a wide range of conditions, and 3) that a low switching frequency can be utilized by the proposed method. A MATLAB/Simulink model and a 1.2kW dual boost converter are built to demonstrate the effectiveness of the proposed method.

• Journal of Navigation and Port Research
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• v.26 no.3
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• pp.295-302
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• 2002

Currently digital communication system adapt various digital modulation schemes. All these communication systems are required to cause the minimum interference to adjacent channels, they must therefore employ the linear power amplifiers. In respect to linear power amplifiers, there are many linearization techniques. Feedforward power amplifier represent very wide bandwidth and high linearization capability. In the feedforward systems overall efficiency is reduced due to the loss of delay line. In this paper, delay filter instead of transmission delay line adapted to get more high efficiency. Experimental results showed that ACLR has improved 17.04dB which is added 2.54dB by using the delay filter.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.2
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• pp.99-106
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• 1998

This paper proposed a speed control system for induction motors robust to variations in torque and parameters by feedforward compensating the current portion of load torque, adding a load torque observer to the conventional PI controller in the indirect vector controlled induction motor system. Computer simulations and exeperimental works using the proposed control confirm that the transient response for the variation of the reference speed and load torque becomes improved, compared with the conventional PI controled method.

• Proceedings of the IEEK Conference
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• 2000.11a
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• pp.341-344
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• 2000

Advanced FeedForward method use Predistortion method and FeedForward method simultaneously. This method better than original Feedforward method in linearity and supply smaller power to pre-power amplifier than different methods, and then it has higher power efficiency and better linearity than original Feedforward method. A linear power amplifier using Advanced feedforward method is designed and fabricated for IMT-2000 transmission system (2110㎒ -2170M㎓). This amplifier's power gain is about 40㏈ and it's 3-rd IMD(Intermodulation distortion) are smaller than about -55㏈c(@ 10MHz).

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.516-517
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• 2015

This paper proposes the feedforward compensation method of output voltage with 3phase AC/DC PWM converter on DC distribution system for improved response. AC/DC PWM converter on DC distribution is required power supply of high quality because of renewable energy sources and load links. In general, Feedforward compensation method of 3phase AC/DC PWM converter receives the sensor input to the output current, load power. Resulting, error of the sensing values and communication cause time delay. Therefore, Feedforward compensation method through only the output voltage is proposed in this paper. The feedforward compensation method through only the output voltage can be applied to the two-level AC/DC PWM converters, as well as multi-level converter or inverter.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.971-982
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• 2015

In order to improve the quality of the billet continuous casting, a two-phase orthogonal power supply (TPOPS) for electromagnetic stirrer is researched, which is composed of three-phase PWM rectifier and three-leg inverter. According to the power analysis of system, the ripple of dc-link voltage is analyzed and its analytical expression is derived. In order to improve the performance of electromagnetic stirring, an integrated control method with feedforward control is proposed for PWM rectifier to suppress the fluctuations of dc-link voltage and provide a stable dc source for inverter. According to the simplified equivalent model, a composite current control method is proposed for inverter. This proposed method can combine the merits of feedforward control with feedback control to effectively improve the dynamic output performance of TPOPS. Finally, a 300kVA prototype of TPOPS is developed, and the results have verified the analysis and control method.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.8 s.111
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• pp.725-731
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• 2006

A novel design of frequency multiplier using a feedforward technique and a defected ground structure(DGS) is proposed. The feedforward loop in the proposed frequency multiplier suppresses the fundamental component $(f_0)$, the dumb-bell or spiral shaped DGS diminish unwanted harmonics such as second, third and fourth. Due to the combination of the feedforward structure and the DGS, only the multiplied frequency component$(2f_0,\;3f_0,\;4f_0)$ appears at the output port and the other unwanted components are suppressed excellently. The frequency multiplier is designed at 1 GHz $(f_0)$, by the proposed technique and measured. The measured output power of $2f_0,\;3f_0$ and $4f_0$ is -2.59 dBm, -5.36dBm and -4.57dBm, respectively, when the input power is 0dBm.