• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.1
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• pp.54-60
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• 2006

A power limiting algorithm is proposed for stable operation of grid-connected inverter in case of grid voltage unbalance considering the operation limit of inverter. During the voltage unbalance the control performance of Inverter. is degraded and the output power contains 120Hz ripple due to the negative sequence of voltage. In this paper, conventional dual sequence current controller is implemented to solve these problems using separated control of positive and negative sequence. Especially the maximum power limit which guarantees the maximum rated current of the inverter is automatically calculated as the instant grid voltage changes. As soon as the voltage recovers the proposed algorithm can return to the normal power control mode accomplishing low voltage ride through. Proposed algorithm is verifed using PSCAD/EMTDC simulations and tested experimentally at 4.4kW wind turbine simulator set-up.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.4
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• pp.229-236
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• 2019

This study proposes a DC-DC converter topology of solid-state transformer for low-voltage DC distribution. The proposed topology consists of a voltage balancer and bipolar DC-DC converter. The voltage and current equations are obtained on the basis of switching states to design the controller. The open-loop gain of the controller is achieved using the derived voltage and current equations. The controller gain is selected through the frequency analysis of the loop gain. The inductance and capacitance are calculated considering the voltage and current ripples. The prototype is fabricated in accordance with the designed system parameters. The proposed topology and designed controller are verified through simulation and experiment.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.4
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• pp.183-190
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• 2003

We report the performance of an open-frame type low-voltage high-current DC-DC converter module developed using an active clamp forward converter circuit and current doubler rectifier. The converter module is designed with the specifications of an 1.8V output voltage, 25A output current, and 36-75V input voltage. The synchronous rectifier is used to reduce the conduction fuss at high current level and current-mode control is adapted to enhance the flexibility in the system configuration. A prototype converter module is successfully implemented within 10mm height and half brick size (58${\times}$61mm), and recorded an 84% efficiency and 4% voltage regulation for the entire input voltage range, thereby demonstrating its application potentials to future telecommunication electronics.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.52 no.4
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• pp.183-183
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• 2003

We report the performance of an open-frame type low-voltage high-current DC-DC converter module developed using an active clamp forward converter circuit and current doubler rectifier. The converter module is designed with the specifications of an 1.8V output voltage, 25A output current, and 36-75V input voltage. The synchronous rectifier is used to reduce the conduction fuss at high current level and current-mode control is adapted to enhance the flexibility in the system configuration. A prototype converter module is successfully implemented within 10mm height and half brick size (58×61mm), and recorded an 84% efficiency and 4% voltage regulation for the entire input voltage range, thereby demonstrating its application potentials to future telecommunication electronics.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.3
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• pp.290-296
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• 2014

This paper presents a design strategy for the control of the Z-source inverter (ZSI). For the Z-network capacitor voltage control, the average current model is derived to describe the dynamics of the voltage control and the controller outputs the average current command for the capacitor. Z-network inductor current reference is derived from the average current model of the Z-network capacitor. The inner current control loop outputs the average voltage command for the Z-network inductor and the shoot-through duty ratio of the ZSI is calculated from the output using the average voltage model of the Z-network inductor. The gain values of the current and voltage controllers are directly obtained by the Z-network parameters and desired bandwidth of each controller without a gain tuning process.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.667-670
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• 1998

Novel bipolar transresistance amplifier(TRA) for high-accuracy current-mode signal processing is described. The TRA consists of two current follower for the current inputs, a current summer for curent-differential, and a voltage follower for the voltage output. The simulation results show that the impedence of the current input and the voltage output is 0.5 $\Omega$ and the 3-dB cutoff frequency when used as a current to voltage converter extends beyond 40 MHz.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.26-30
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• 1999

The constraint condition is the stator voltage and the stator current to operate the motor in the flux weakening region. The maximum current is limited by the inverter current rating and the machine thermal rating. Given DC link voltage to control the motor in the flux weakening the maximum voltage is determined by considering PWM strategy, dead time, voltage drop of the inverter switching device, and the margin of the voltage for current forcing. In this paper, the new method to determine the available maximum voltage is derived by the analythic method and by considering the factors of the voltage drop. So Determining the maximum voltage is very useful to enlarge the speed operation region in the flux weakening operation, the utility of the maximum voltage is increased.

• Proceedings of the IEEK Conference
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• summer
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• pp.66-69
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• 2004

This work is the study of Voltage-Down Converter used as internal supply voltage having large current driving and stable voltage level at any variation of process, voltage, and temperature(P.V.T). It converts VDD(external supply voltage) into $V_{1NT}(internal\;supply\;voltage).$ From the simulation results, a new Voltage-Down Converter has large current driving and a little stand-by current under lower supply voltage than conventional circuit. And bad characteristic of VINT, peaking, was eliminated. Start-up circuit for BGR is also added to one circuit, which consumes less current dissipation than convention circuit

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.9
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• pp.1648-1653
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• 2006

In this paper, transport characteristics have been investigated using analytical current-voltage model for double gate MOSFET(DGMOSFET). Scaling down to 100nm of gate length for MOSFET can bring about various problems such as a threshold voltage roll-off and increasing off current by tunneling since thickness of oxide is down by 1.fnm and doping concentration is increased. A current-voltage characteristics have been calculated according to changing of channel length,using analytical current-voltage relation. The analytical model has been verified by calculating I-V relation according to changing of oxide thickness and channel thickness as well as channel length. A current-voltage characteristics also have been compared and analyzed for operating temperature. When gate voltage is 2V, it is shown that a current-voltage characteristic in 77K is superior to in room temperature.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.2
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• pp.104-109
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• 2014

To operate organic light emitting device (OLED) with alternating current (AC) power source without AC/DC(direct current) converter, we fabricated the fluorescent OLED and measured the emission characteristics with AC and DC. The OLED operated by AC showed higher maximum current efficiency of 8.2 cd/A and maximum power efficiency of 8.3 lm/W. But current efficiency and power efficiency of AC driven OLED showed worse than DC driven OLED at high voltage above 10 V. This result can be explained by the peak voltage of AC was $\sqrt{2}$ times than DC, In case of low driving voltage the emission characteristics were improved by the peak voltage of AC, but in case of high driving voltage the emission efficiencies were decreased by the roll off phenomena. Finally, serial OLED arrays using twelve OLEDs driven by AC 110 V showed average voltage of 9.17 V, voltage uniformity of 99.0%, average luminance of $1,175cd/m^2$, luminance uniformity of 94.4%.