• Proceedings of the KIEE Conference
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• 2007.11c
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• pp.88-92
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• 2007

In this paper, the basic experiment, electrolytic cell design and basic manufacturing have been made to interpret the characteristics of Hydrogen-Oxygen-Gas-Generator. As for the detailed matters, the data research on basic technology on Hydrogen-Oxygen-Gas and analysis on characteristics of Hydrogen-Oxygen-Gas from basic experiment. Also the experiment of characteristics and comparative evaluation between constant current source using IGBT converter from existing method and constant current source using new phase shift PWM control method converter. As results when it has injected constant DC current, we has compared Gas quantities by variable ripple frequencies using phase shift PWM control method converter. Therefore, in linear region, it has not different Gas quantities by constant DC current and by phase shift PWM control method converter. Also, it has increased Gas quantities wilder linear region when put ripple frequency at saturation region. Through, Gas quantities and input power, it has acquired higher input power per Gas quantities at put pulse curren. Therefore, when designing converter or inverter for electrolysis, which has ripple current.

• Journal of Power Electronics
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• v.15 no.6
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• pp.1429-1437
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• 2015

A new parallel hybrid soft switching converter with low circulating current losses during the freewheeling state and a low output current ripple is presented in this paper. Two circuit modules are connected in parallel using the interleaved pulse-width modulation scheme to provide more power to the output load and to reduce the output current ripple. Each circuit module includes a three-level converter and a half-bridge converter sharing the same lagging-leg switches. A resonant capacitor is adopted on the primary side of the three-level converter to reduce the circulating current to zero in the freewheeling state. Thus, the high circulating current loss in conventional three-level converters is alleviated. A half-bridge converter is adopted to extend the ZVS range. Therefore, the lagging-leg switches can be turned on under zero voltage switching from light load to full load conditions. The secondary windings of the two converters are connected in series so that the rectified voltage is positive instead of zero during the freewheeling interval. Hence, the output inductance of the three-level converter can be reduced. The circuit configuration, operation principles and circuit characteristics are presented in detail. Experiments based on a 1920W prototype are provided to verify the effectiveness of the proposed converter.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.12
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• pp.83-87
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• 2015

This paper presents a simple notch filter, which is so suitable for three-phase unbalanced and distorted power line. In the d-q synchronous transformation, three-phase unbalanced and distorted voltages generate lots of ripple voltages on d-q axes. The ripples make disturbances on controllers such as PLL of phase tracking. Unbalanced state makes ripple of double the frequency of power line. Odd harmonics 5th and 7th on the line make even 4th and 6th ripples on d-q axes due to the rotating reference frame, respectively. Cascaded two comb filters, delay lines 1/4T and 1/8T, are adopted for the ripple rejection. The filter rejects harmonics 2nd, 4th, 6th, 10th and so on. They are very effective to remove the ripples of both unbalance and distortion. The filter, implemented by two FIFOs on an experimental system, is adopted on a PLL controller of power line phase tracking. Through the simulation and experimental results, performance of the proposed comb filter has been validated.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.5
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• pp.377-387
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• 2012

A single-phase grid-connected PV system is known as suitable for housing of less than 3 kW. The DC link voltage in a single-phase PV system has necessarily twice component of fundamental wave. It makes high THD in the grid current. According to the problem, power quality is lower. Many engineers have studied about this problem. The most simple method is to use low pass filter on DC link voltage control. However it is affected by DC link voltage control bandwidth. If cutoff frequency is reduced to increase the performance of low pass filter, it also lowers DC link voltage control bandwidth. Second method is using band stop filter, it works good on steady state but not good on transient state. This paper proposes the new method for removing ripple voltage to get an exact current reference. It improves the responses on steady state and transient state. The performance was verified through computer simulation using MATLAB and actual experiments.

• New & Renewable Energy
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• v.3 no.4
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• pp.69-76
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• 2007

In this paper, a PV multi-string PCS with a grid-connection is proposed. An improved MPPT algorithm for the PV multi-string PCS is suggested. Each PV string has its own MPP tracker and the proposed MPPT algorithm prevents LMPP tracking due to power ripple. In the PV PCS with single-phase inverter has a large current ripple at twice the grid frequency. The current ripple reduction algorithm without external component is suggested. Also, this paper proposes a simple control method to achieve sharing of the PV string voltage and current among the interleaved parallel boost converters. All algorithms and controllers are implemented on a single-chip microcontroller. Experimental results obtained on a 3kW prototype show high performance of the proposed PV multi-string PCS.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.963_964
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• 2009

This paper presents an output ripple reduction of Active-Clamp Forward Converter, which is mainly composed of interleaving two active-clamping forward converters. By interleaving, Output ripple is reduced. The leakage inductance of the transformer or an additional resonant inductance is employed to achieve ZVS during the dead times. The duty cycles are not limited to be equal and within 50%. The complementary switching and the resulted interleaved output inductor currents diminish the current ripple in output capacitors. Accordingly, the smaller output chokes and capacitors lower the converter volume and increase the power density. Detailed analysis of this ouput reduction of Active-Clamp Forward Converter is described.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.255-258
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• 2007

In this paper, a PV multi-string PCS with a grid-connection is proposed. An improved MPPT algorithm for the PV multi-string PCS is suggested. Each PV string has its own MPP tracker and the proposed MPPT algorithm prevents LMPP tracking due to power ripple. In the PV PCS with single-phase inverter has a large current ripple at twice the grid frequency. The current ripple reduction algorithm without external component is suggested. Also, this paper proposes a simple control method to achieve sharing of the PV string voltage and current among the interleaved parallel boost converters. All algorithms and controllers are implemented on a single-chip microcontroller. Experimental results obtained on a 3kW prototype show high performance of the proposed PV multi-string PCS.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2000.11a
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• pp.219-224
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• 2000

This paper presents a ripple reduction of BLDC motor using TMS320F240. A fault of permanent magnet(PM) BLDC motor possible to miniaturization and high-output is to be difficult to reduce speed-ripple at low speed region. An existing solution is to be use of PWM waveform by PI control with computing control angle of 60$^{\circ}$. The new family of DSP controllers provides a single chip solution by integrating on-chip not only a high computational power but also, all the peripherals necessary for electric motor control. This paper gives an advanced solution of the SVPWM technique for the purpose of reducing control angel rather than 60$^{\circ}$. This technique gives an excellent speed ripple characteristic.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.3
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• pp.538-543
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• 2011

In this paper, design and control of an interleaved boost converter for multi-string PV Inverter are discussed. Interleaved Boost converter can reduce current ripples at input and output side by cancelling an each phase of inductor currents. Therefore, it contributes to increase efficiency and downsize the whole system volume, cost. One of the advantages of the multi-string system is easy to expand power capacity by connecting the converter modules in parallel. In order to reduce current ripples, the inductor currents on each phase are controlled independently in the converter module, and communication between the converter modules is required for further ripple current reduction. Current control algorithm for the balance of the each phase ripple currents and synchronization of the converter modules based on communication are proposed and implemented in the DSP programming. 10kW prototype of the multi-string converter module is assembled and experimental results are presented to verify the proposed ripple current reduction methods.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.276-279
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• 2001

Direct torque control(DTC) is known to produce quick response in ac drives. Some drawbacks of the classical DTC are the relatively large torque ripple in a low speed range and notable current pulsation during steady state. They are reflected speed response and increased acoustical noise. In this paper, The DTC quick response are preserved at transient state, while better qualify steady state performance is produced by Space Vector Modulation(SVM). It is able to reduce the acoustical noise, torque ripple and current pulsation during steady state. The system presented are closed loop stator flux and torque observer for wide speed range that inputs are currents and voltages sensing of motor terminal. Simulation results for the 2.2kw general purposed induction motor are presented and discussed.