• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.308-311
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• 2001

Most of the battery charger for electric powered forklift truck are controlled by the method of 3-phased constant current and constant voltage. However, these chargers have several disadvantages like a large charger capacity, and a short battery life time. This paper presents a digital type battery charger based on multi-mode control adding a constant power control and several assistant controls in the conventional control. The whole control system is performed by a low cost one-chip micro-controller and completely digitize. So we can get a high precision control and a good reliability.

• Proceedings of the KIEE Conference
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• 1993.07a
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• pp.189-191
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• 1993

A systematic procedure for the elements of system matrix in multimachine systems with loads is suggested for the small-signal stability studies. Synchronous machines are represented by either a two-axis model or classical model. The interrelationship of submatrices of system matrix is investigated. Once elements of one submatrix are determined, they can be used to calculate the elements of the other submatrix. It is illustrated for three machine and nine bus multimachine systems with constant impedance loads, constant MVA load, constant current and power factors.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.7
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• pp.530-533
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• 2010

The proton exchange membrane fuel cell (PEMFC) holds great promise of clean power. However, in practical applications which use the PEMFC as the power source, the output voltage from the fuel cell undergoes a transient response especially during acceleration and deceleration. This paper presents the relationships between the charge curves of the internal voltage rise, discharge curves of the internal voltage drop, the voltage with a time constant $V_{\tau}$ and finally, the load and time constant $\tau$ of $FC_1$ and $FC_2$, connected both in series and in parallel.

• Journal of Power Electronics
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• v.18 no.6
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• pp.1720-1728
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• 2018

This paper proposes a novel soft starting algorithm by using PWM inverter technique to control an amplitude of the motor starting current at a single-phase induction motor (SPIM). Traditional SPIM starting methods such as a Split-Phase, Capacitor-Start, Permanent-Split Capacitor (PSC), Capacitor-Start Capacitor-Run (CSCR), basically cannot control the magnitude of starting current due to the fixed system structures. Therefore, in this paper, a soft starting algorithm based on a proportional resonant (PR) control with a variable and constant frequency is proposed to reduce the inrush current and starting up time. In addition, a transition algorithm for operation modes is devised to generate a constant voltage and constant frequency (CVCF). The validity and effectiveness of the proposed soft starting method and transition algorithm are verified through experimental results.

• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.201-202
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• 2018

본 논문에서는 넓은 범위의 입력전압에서의 빠른 응답속도를 가진 고승압 양방향 컨버터를 제안한다. 제안하는 시스템은 2대의 Buck컨버터와 SRC(Seris Resonant Covnerter)로 구성된 3-stage 구조이며, 고승압이 가능하고 넓은 입력전압 범위에서 고효율을 성취할 수 있다. 또한 제안하는 컨버터는 모든 전압범위에서 빠른 응답속도로 제어를 하며 CC(Constant Current), CV(Constant Voltage), CP(Constant Power) 및 Pulse 동작을 수행한다. 제안하는 양방향 컨버터의 1.8kW급 시작품으로 실험을 통하여 타당성을 검증하였고, 최고효율 96%, 정격효율 90.8%를 달성하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.20 no.2
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• pp.182-192
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• 2015

This study develops a digital control scheme with power factor correction for a front-end converter in an electric vehicle battery charger. The front-end converter acts as the boost-type switching-mode rectifier. The converter assumes the two roles of the battery charger, which include power factor control and robust charging performance. The proposed control scheme consists of a charging control algorithm and a grid current control algorithm. The scheme aims to obtain unity input power factor and robust performance. Based on the linear average model of the converter, a constant-current constant-voltage charging control algorithm that passes through only one proportional-integral controller and a current feed-forward path is proposed. In the current control algorithm, we utilized a second band pass filter, a single-phase phase-locked loop technique, and a duty-ratio feed-forward term to control the grid current to be in phase with the grid voltage and achieve pure sinusoidal waveform. Simulations and experiments were conducted to verify the effectiveness of the proposed control scheme, both simulations and experiments.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.950-954
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• 1998

This paper describes a development of traction unit for 2-motor driven electric vehicle (EV). The traction unit is consisted with an interior permanent magnet synchronous motor (IPMSM), a reduction gear and an inverter for electric vehicle that is driven by 2 motors without differential gear. For traction unit, prototype IPMSM and inverter have been developed. The IPMSM was designed by CAD program that was developed with both equivalent circuit method and FEM. Also the inverter was developed to drive 2 motors with 6 legs IGBT switches in a control board. The vector control algorithm was implemented with maximum torque control method in the constant torque region and field weakening control method in the constant power region considering inverter capacity. To verify that the traction unit is more high efficiency and has more high power density than a traction unit with induction motor with the same power, we would like to show the results about the design and analysis of the IPMSM and the experiment results about the traction unit.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.12
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• pp.1740-1744
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• 2017

This paper describes the preparation and characteristics of a battery capacitor and module for solar power system. A cylindrical 30,000F battery capacitor ($60{\times}138mm$) was assembled by using the $LTO(Li_4Ti_5O_{12})$ electrode as an anode and $NMC(LiNiMnCoO_2)-LCO(LiCoO_2)$ as a cathode. The battery capacitor has reduced energy density and power density under high CC(constant current) and CP(constant power) conditions. Battery capacitor module (16V, 11Ah) was fabricated using an asymmetric hybrid capacitor with a capacitance of 30,000F. In order to determine the characteristics of the battery capacitor Module for solar power system, battery capacitor cells were connected in series with active balancing circuit. As a result of measuring the 100w LED lamp, it was discharged at the voltage of 15V~10V, and the compensation time at discharge was measured to be about 4979s. Experimental results show that it can be applied to applications related to solar power system by applying battery capacitor module.

• Journal of Communications and Networks
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• v.12 no.5
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• pp.459-465
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• 2010

A new blind equalization algorithm that is based on maximizing the probability that the constant modulus errors concentrate near zero is proposed. The cost function of the proposed algorithm is to maximize the probability that the equalizer output power is equal to the constant modulus of the transmitted symbols. Two blind information-theoretic learning (ITL) algorithms based on constant modulus error signals are also introduced: One for minimizing the Euclidean probability density function distance and the other for minimizing the constant modulus error entropy. The relations between the algorithms and their characteristics are investigated, and their performance is compared and analyzed through simulations in multi-path channel environments. The proposed algorithm has a lower computational complexity and a faster convergence speed than the other ITL algorithms that are based on a constant modulus error. The error samples of the proposed blind algorithm exhibit more concentrated density functions and superior error rate performance in severe multi-path channel environments when compared with the other algorithms.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.83-84
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• 2010

This paper reviews the performance difference between constant voltage control and constant current control in LED driver. Simulations of both control methods are performed for performance comparison especially with temperature variation. The results show that constant current control method is inherently better than constant voltage control for LED drive.