• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.2
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• pp.408-414
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• 2005

The VCDRO(Voltage Controlled Dielectric Resonate. Oscillator) with low phase noise is designed using nonlinear analysis, and its phase noise characteristics are compared with that of Lesson's equation. The microstripline coupled with dielectric resonator is realized as a high impedance inverter to improve the phase noise performance, and the quality factor of resonator circuit can be transferred to active device with the enhanced the loaded quality factor. The worst case and part stress analyses are achieved to obtain the high reliability of VCDRO and the reliability analysis is accomplished to estimate the probability of operation at the end of life. The developed VCDRO has the oscillating tuning factor of 0.56MHZ1V for the control voltage range of 0-l2V. This VCDRO requires the DC power of 136mW. The phase noise characteristics exhibit good performances of -94.18dBc/Hz (a)10KHz and -116.3dBc/Hz (a)100KHz. And, the output power over 7.33dBm is measured.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.2
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• pp.105-111
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• 2009

The powers used in the motor drive system are mostly DC sources like batteries. Even AC powers in some systems are generated from DC sources by the inverter. It is can be forecasted that the DC-link communications will be widely used in various industrial fields. In this paper a novel BLDC motor drive system using DC-link communications is proposed. The characteristic of this system Is that the communication only needs 2 DC lines. There are not additional lines to translate the reference signals. And the reliability o3 the system is ensured especially under some terrible circumstances. The number of lines can be minimized when the DC-link communication method is applied in the multi motor control system and the slip ring design also can be simplified when this method is applied in rotation machines. The proposed motor system is clarified by the PSIM and MATLAB simulations and tested through the hardware prototype.

• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.325-330
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• 2012

A single-phase PVPCS(photovoltaic power conditioning system) that contains a single phase dc-ac inverter tends to draw an ac ripple current at twice the out frequency. Such a ripple current may shorten passive elements life span and worsen output current THD. As a result, it may reduce the efficiency of the whole PVPCS system. In this paper, the ripple current propagation is analyzed, and two methods to reduce the ripple current are proposed. Firslyt, this paper presents notch filter with IP voltage controller to reject specific current ripple in single-phase PVPCS. The notch filter can be designed that suppress just only specific frequency component and no phase delay. The proposed notch filter can suppress output command signal in the ripple bandwidth for reducing output current THD. Secondly, for reducing specific current ripple, the other method is feed-forward compensation to incorporate a current control loop in the dc-dc converter. The proposed notch filter and feed-forward compensation method have been verified with computer simulation and simulation results obtained demonstrate the validity of the proposed control scheme.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.5
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• pp.1052-1058
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• 2005

This paper dealt with the design and fabrication of a low frequency electronic ballast for ruh attracting lamps. The proposed electronic ballast was composed of a full-wave rectifier, a step don converter operated as a constant power controled current source, an inverter operated by 130 Hz square wave, and an ignition circuit. An acoustic resonance phenomenon of discharge lamps could be eliminated by application of 130 Hz square wave. Also, a circuit of high voltage pulse generation for lamp ignition was added to the ballast. From the experimental results, voltage and current of the lamp operated by the electronic ballast were estimated 132.5 V and 7.6 A, respectively. and the power consumption was about 1,000 W. The weight of the ballast, which is one of important advantages, was reduced to one-fifth of conventional magnetic ballasts.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.2
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• pp.125-131
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• 2001

This paper presents a application of vector control strategy to 1.2MVA traction drive for railway vehicle. The vector control required the control of the phase and amplitude of output voltage vector. But in case of traction system for railway vehicle, the one-pulse mode is used at high speed region in order to utilize the link voltage fully. So it is impossible to control the flux and torque axis current instantaneously and independently in the region. So this paper proposes a mixed control algorithm, where the vector control strategy at low speed region and slip-frequency control strategy at high speed region is used. And precise switching technique between the two different control strategy is proposed. The proposed strategy is verified by experimental results with a 1.2MVA traction drive system with four 210kW induction motors.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.4
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• pp.309-317
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• 2000

This paper presents the switching angle and voltage to maximize torque/efficiency and minimize torque ripple in the 4-phase 6-poles Switched Reluctance Motor(SRM). SRM drive has high saturation and nonlinear characteristics of inductance. So we cannot hard to find optimal condition by using analytic method. Therefore it is hard to find the operating the switching angle and voltage through the approximated analysis and computer simulation by using SIMULINK according to the speed and torque required by load. From the results, we can say that the optimum average voltage is determined by the load only and the speed is determined by the optimum turn-on/off angle only. And the maximum efficiency and minimum torque ripple depend on switching angle, not on voltage. And then one-chip microcontroller controls the switching angle and voltage of an asymmetrical inverter in the SRM driver. This drive method, which is expect that the driving methods, which are maximizing torque/efficiency and minimizing torque ripple, will be suitable for the electric vehicle, the industrial application and household appliances.

• Journal of the Korean Society of Marine Environment & Safety
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• v.19 no.1
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• pp.66-70
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• 2013

The input current of three phase rectifier which is mainly used in the propulsion system of the electric propulsion ship includes a variety of low order harmonics. To reduce these harmonics, the power conversion system, used in the large vessels which high power is required, is currently used the rectifiers of 12-pulse output, but it still has a problem that occurs $12{\pm}1$ harmonics. Also, in the case of the direct torque control technique which is widely used for the speed and torque control, the torque ripple is severe and the input current of motor has greatly included harmonics by the switching of the inverter. In order to reduce harmonics and improve the performance of torque control, this paper presents that the auxiliary supply assisted into the 12-pulse rectifier of the electric propulsion system using direct torque control technique. We confirm the validity of the proposed method through the simulation under the environment of a real vessel system.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.11
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• pp.1663-1668
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• 2017

A BLDC motor with higher number of phases has several advantages, compared to the conventional three-phase BLDC motors. It can reduce the commutation torque ripple and the iron loss without increasing the voltage per phase and increase the reliability and power density. Higher number of phases increase the torque-per-ampere ratio for the same machine volume and output power by widening the electrical conduction period. In this paper, the proposed seven-phase BLDC motor drive system is made into several functional modular blocks, so that it can be easily extended to other ac motor applications: back-EMF block, hysteresis current control block, pwm inverter block, phase current block, and speed/torque control block. Also in a system of BLDC motor drive, the PI controller has been widely used in the speed controller because of the simple implementation. To obtain a good speed response in a general drive system using the PI controller, the high bandwidth of a controller is established. therefore, in this paper, a Fuzzy controller is applied to the 7-phase BLDC motor drive system in order to improve the speed control performance. The Fuzzy controller is compared with a conventional PI controller through the experiment with respect to speed dynamic responses. These experimental results show that the Fuzzy controller of the 7-phase BLDC motor drive system is superior over the conventional PI controller. The algorithm using the Fuzzy controller can improve a comfortable ride in the field of high performance 7-phase BLDC motor drive applications.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.4
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• pp.335-344
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• 2004

A low phase noise EQM(Engineering Qualified Model) LO(Local Oscillator) has been developed for Ka-band satellite transponder. A VCDRO(Voltage Controlled Dielectric Resonator Oscillator) is also designed using a high impedance inverter coupled with dielectric resonator to improve the phase noise performances out of the loop bandwidth. The mechanical analysis fur housing and the thermal analysis fur circuit board are achieved. This EQM LO is applied to Ka-band satellite transponder of EQM level after environmental experiments for space application. The LO has the harmonic suppression characteristics above 52 ㏈c and requires low power consumption under 1.3 watts. The phase noise characteristics are exhibited as -101.33 ㏈c/㎐ at 10 ㎑ offset frequency and -114.33 ㏈c/㎐ at 100 ㎑ offset frequency, with the output power of 14.0 ㏈m${\pm}$0.17 ㏈ over the temperature range of -15∼＋65$^{\circ}C$.

• Journal of Power Electronics
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• v.14 no.5
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• pp.1047-1056
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• 2014

In most grid-connected inverters (GCI) with an LCL filter, since the design of both the LCL filter and the controller is done separately, considerable tuning efforts have to be exerted when compared to inverters using an L filter. Consequently, an integrated co-design of the filter and the controller for an LCL-type GCI is proposed in this paper. The control strategy includes only a PI current controller and a proportional grid voltage feed-forward controller. The capacitor is removed from the LCL filer and the design procedure starts from an L-type GCI with a PI current controller. After the PI controller has been settled, the capacitor is added back to the filter. Hence, it introduces a resonance frequency, which is identified based on the crossover frequencies to accommodate the preset PI controller. Using the proposed co-design method, harmonic standards are satisfied and other practical constraints are met. Furthermore, the grid voltage feed-forward control can bring an inherent damping characteristic. In such a way, the good control performance offered by the original L-type GCI and the sharp harmonic attenuation offered by the latter designed LCL filter can be well integrated. Moreover, only the grid current and grid voltage are sensed. Simulation and experimental results verify the feasibility of the proposed design methodology.