• Proceedings of the KSR Conference
• /
• 2008.11b
• /
• pp.179-184
• /
• 2008

This paper presents the design of the feed forward controller to improve on the non-interference control performance of a single PWM converter in parallel for high-speed trains. The feed forward controller is designed to minimize the interference generated by converter switching in parallel operation of PWM converters. The gain value of the feed forward controller is calculated by inductance values of the input transformer. However, it is difficult to decide this gain value exactly because inductance values are changed by the operation condition of an input transformer. In this paper, the proposed design of feed forward controller can exactly decide the gain value using the leakage inductances estimated by detecting the variation of input current. the validity of the proposed feed forward controller is proved through the simulation results.

• Proceedings of the KIPE Conference
• /
• 2019.07a
• /
• pp.153-155
• /
• 2019

This paper proposes a two-phase interleaved bridgeless single-stage ac-dc converter with magnetic integration that can achieve CCM power factor correction without input current sensing. All switches achieve ZVS turn-on and all diodes achieve ZCS turn-on for the whole grid cycle. SDAB-based modulation strategy is applied which results in simple power control and wide range output voltage. A flux cancellation method to integrate the interleaved transformer is firstly proposed in this paper to reduce the core size and loss. Experimental results on a 1.7-kW, 50kHz prototype are given to verify the principle and advantages of the proposed ac-dc converter.

• ETRI Journal
• /
• v.46 no.1
• /
• pp.118-126
• /
• 2024

In human conversations, listeners often utilize brief backchannels such as "uh-huh" or "yeah." Timely backchannels are crucial to understanding and increasing trust among conversational partners. In human-machine conversation systems, users can engage in natural conversations when a conversational agent generates backchannels like a human listener. We propose a method that simultaneously predicts backchannels and recognizes speech in real time. We use a streaming transformer and adopt multitask learning for concurrent backchannel prediction and speech recognition. The experimental results demonstrate the superior performance of our method compared with previous works while maintaining a similar single-task speech recognition performance. Owing to the extremely imbalanced training data distribution, the single-task backchannel prediction model fails to predict any of the backchannel categories, and the proposed multitask approach substantially enhances the backchannel prediction performance. Notably, in the streaming prediction scenario, the performance of backchannel prediction improves by up to 18.7% compared with existing methods.

• Proceedings of the KIPE Conference
• /
• 2000.07a
• /
• pp.355-359
• /
• 2000

This paper deal with the harmonic reduction technique in three-phase square-wave inverter system formed by single-phase inverter. To reduce the harmonics six single-phase inverters are used for forming multi-phase inverter and zig-zag connected output transformer for eliminating the harmonic 6(2k-1)$\pm$1 orders. And an ac filter is furnished at output side. Computer simulations show that the THD of the output voltage can be reduced immensely.

• 전기의세계
• /
• v.28 no.3
• /
• pp.51-56
• /
• 1979

The purpose of this paper is to study the conversion of single phase to three phase. In the proceeding of phase conversion, it is very convinence to convert two-phase from single phase using cycloconverter before and then two to three phase by scott connection transformer. There are also systematized zero-crossing, mono vibrator and ring counter circuit for the gate trigger circuits of cycloconverter. The wave forms of three phase by experimental results are analyzed and discussed the relation of phase difference among them.

• Proceedings of the KIPE Conference
• /
• 1998.07a
• /
• pp.401-404
• /
• 1998

This paper proposes a new soft switching single stage AC/DC full bridge converter with unit power factor and isolated output. This circuit shows that it is possible to combine the boost converter which is for PFC(Power Factor Correction) and full bridge converter which is for DC/DC converter. A simple auxiliary circuit which includes neither lossy components nor active switches eliminates ringing of secondary side of the transformer. The characteristics of the proposed circuit are investigated and the validity is verified by the simulation results.

• Journal of IKEEE
• /
• v.26 no.3
• /
• pp.456-461
• /
• 2022

In this paper, a two-stage single-ended power amplifier (PA) with broadband gain characteristics was presented by utilizing a radio frequency (RF) transformer (TF), which is essential for a differential amplifier. The bandwidth of a PA can be improved by designing TF to have broadband characteristics and then applying it to the inter-stage matching network (IMN) of a PA. For broadband gain characteristics while maintaining the performance and area of the existing PA, an IMN was implemented on an monolithic microwave integrated circuit (MMIC) and a multi-layer printed circuit board (PCB), and the simulation results were compared. As a result of simulating the PA module designed using InGaP/GaAs HBT model, it has been confirmed that the PA employing the proposed design method has an improved fractional bandwidth of 19.8% at a center frequency of 3.3GHz, while the conventional PA showed that of 11.2%.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• v.5B no.3
• /
• pp.277-282
• /
• 2005

This paper describes a step-down AC voltage regulator using an AC chopper and auxiliary transformer, which is a series connected to the main input. The detail design of the AC regulator, logic and PWM pattern of the AC chopper is described and the three-phase AC regulator using two single­phase AC choppers with a three transformer configuration is proposed for three-phase application. The proposed three-phase system has the advantages of lower system cost due to reduced switch number and gate driver circuit as well as advantages of decreased size and weight because it uses a series compensated scheme. The proposed AC regulator has many benefits such as fast voltage control, high efficiency and simple control logic. Experimental results indicate that it can be used as a step-down AC voltage regulator for power saving purposes very efficiently.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
• /
• 2002.02a
• /
• pp.233-236
• /
• 2002

A conceptual design of single phase high Tc superconducting (HTS) 1MVA transformer was presented in this paper. The rated voltages of each sides of the transformer are 22.9kV /6.6kV respectively. Double pancake windings of BSCCO-2223 HTS tape and the room temperature shell type core are adopted. The HTS tapes of windings are going to be cooled down to 65K by sub-cooled liquid nitrogen. A cryostat made of nonmagnetic and nonconducting material with a bore is going to be used in order to locate the core out of the cryostat. This conceptual design will be modified and a fabrication of the machine is going to be based on the presented design in this paper.

• Proceedings of the KIEE Conference
• /
• 2001.07b
• /
• pp.1281-1283
• /
• 2001

An investigation into power conditioners that interface with photovoltaic array and utilities has been completed. The rating for this investigation is residential system(3-5kW) that interface with a 220V single phase utility connection. As the result of this investigation, a 3kW high frequency PWM IGBT inverter feeding a high frequency isolation transformer with a sinusoidal current wave was selected. The output of the transformer rectified with a diode bridge rectifier four IGBT, used as 60Hz switched, reverse the polarity of the rectified current on every other half cycle of the utility voltage. Even though the high frequency link system used more power semiconductors a net size, weight, and parts cost saying result compared to the other systems due to elimination of 60Hz transformer.