• Journal of Power Electronics
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• v.8 no.1
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• pp.10-22
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• 2008

The wind-driven doubly fed induction generator (DFIG) is currently under pressure to be more grid-compatible. The main concern is the fault ride-through (FRT) requirement to keep the generator connected to the grid during faults. In response to this, the paper introduces a novel model and new control scheme for the DFIG. The model provides a means of direct stator power control and considers the stator transients. On the basis of the derived model, a robust linear quadratic (LQ) controller is synthesized. The control law has proportional and integral actions and takes account of one sample delay in the input owing to the microprocessor's execution time. Further, the influence of the grid voltage imperfection is mitigated using frequency shaped cost functional method. Compensation of the rotor current pulsations is proposed to improve the FRT capability as well as the generator performance under grid voltage unbalance. As a consequence, the control system can achieve i) fast direct power control without instability risk, ii) alleviation of the problems associated with the DFIG operation under unbalanced grid voltage, and iii) high probability of successful grid FRT. The effectiveness of the proposed solution is confirmed through simulation studies on 2MW DFIG.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.8
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• pp.64-70
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• 2007

The electrical accident results from an insulation blackdown by over-voltage, an overheating by the excess of allowable current, a deterioration performance by the passage of time, and so on. This paper discusses how to improve the power control system of PCB in water purifier. The protecting device of present power supply control system in water purifier is composed of the varistor device which acts only for impulse-type surges. So the present system can not be protected others except the surge of impulse-type. The newly-suggested power control system in this paper is designed to protect the system by disconnecting power supply through SSR(Solid State Relay) if the value of input voltage is exceeded the setting value.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.56 no.1
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• pp.45-50
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• 2007

In this paper, this paper discusses how to improve the power control system of cold and hot water purifiers, in particular, system protecting device against abnormal voltage. The existing power supply control system came with a protecting device composed of varistor device only for impulse-type surges. Even though the existing system senses surge other than impulse-type, the system can not be protected. Accordingly, a new type of power control system was designed to protect the system from surge and ultimately prevent electricity accidents. The power control system suggested in this paper will be designed to protect the system by sensing input voltage and discontinuing power supply by means of SSR if voltage exceeding set value is sensed. To test the designed system, surge was imposed on the existing system and processes of system failure were experimented before safety of the designed power control system was simulated via P-spice program developed by Orcad in order to examine safety and reliability of the system.

• 전자공학회논문지 IE
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• v.49 no.1
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• pp.18-23
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• 2012

In this paper, a potable device application for DC-DC converter was designed for voltage protection circuit. Voltage protection circuit to offer the under voltage lock out and over voltage protection consists of a comparator and bais circuits were implemented using. XFAB 1um CMOS process, SPICE simulations was confirmed through the characteristics. Simulation results, under voltage lock out input voltage is 4.8 V higher when the turn-on and, 4.2 V less when turn-off. When the input voltage is low voltage is applied can be used to prevent malfunction of the circuit. Over voltage protection is 3.8 V reference voltage when the output voltage caused by blocking circuit prevents device destruction can be used to improve the stability and reliability. The virtual control circuits of the DC-DC converter connected. According to the results of the abnormal voltage, voltage protection circuit behavior was confirmed. The proposed voltage protection circuit of the DC-DC converter cell is useful are considered.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.107-109
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• 2006

The additional matters appear to be considered in several aspects for building up power-quality measuring system of transmission system(high voltage system) compared to distribution system(middle or low voltage system). Like in distribution system, input signals are also received from PT and CT source of voltage and current respectively in transmission system and applied in accordance with a certain rate. In this case, very big error rate can be occurred according to the specification of the measuring system as the applying rate is bigger than in distribution system beyond comparison. In addition, when the abnormal signal occurred such as sag/swell, interruption, transient etc., power quality of other sites linked to the system also should be checked to find the accurate cause of the abnormal power-quality signals from the corresponding site. Accordingly, the accurate diagnosis on the condition of Power quality for the system depends on the way how the synchronization system is brought along for each site. This paper will suggest the solution for the most effective system building focused on how to solve the problem of the error rate and synchronization described in the above when building up the measuring system of power quality for transmission system.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.432-434
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• 2006

The additional matters appear to be considered in several aspects for building up power-quality measuring system of transmission system(high voltage system) compared to distribution system(middle or low voltage system). Like in distribution system, input signals are also received from PT and CT source of voltage and current respectively in transmission system and applied in accordance with a certain rate. In this case, very big error rate can be occurred according to the specification of the measuring system as the applying rate is bigger than in distribution system beyond comparison. In addition, when the abnormal signal occurred such as sag/swell, interruption, transient etc., power quality of other sires linked to the system also should be checked to find the accurate cause of the abnormal power-quality signals from the corresponding. site. Accordingly, the accurate diagnosis on the condition of power quality for the system depends on the way how the synchronization system is brought along for each site. This paper will suggest the solution for the most effective system building focused on how to solve the problem of the error rate and synchronization described in the above when building up the measuring system of power quality for transmission system.

• Journal of Powder Materials
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• v.22 no.5
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• pp.331-336
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• 2015

We report on the succesful fabrication of ZnO nanorod (NR)-based robust piezoelectric nanogenerators (PNGs) by using Cu foil substrate. The ZnO NRs are successfully grown on the Cu foil substrate by using all solution based method, a two step hydrothermal synthesis. The ZnO NRs are grown along c-axis well with an average diameter of 75~80 nm and length of $1{\sim}1.5{\mu}m$. The ZnO NRs showed abnormal photoluminescence specrta which is attributed from surface plasmon resonance assistant enhancement at specific wavelength. The PNGs on the SUS substrates show typical piezoelectric output performance which showing a frequency dependent voltage enhancement and polarity dependent charging and discharging characteristics. The output voltage range is 0.79~2.28 V with variation of input strain frequency of 1.8~3.9 Hz. The PNG on Cu foil shows reliable output performance even at the operation over 200 times without showing degradation of output voltage. The current output from the PNG is $0.7{\mu}A/cm^2$ which is a typical out-put range from the ZnO NR-based PNGs. These performance enhancement is attributed from the high flexibility, high electrical conductivity and excellent heat dissipation properties of the Cu foil as a substrate.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.2
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• pp.84-94
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• 2013

In case when the existing TRIAC phase controlled dimmer is drove for the LED lighting equipments, there are many problems such as the LED flicker in low phase-angles, the acoustic noise and elements damage by increase of the peak voltage in the input filter capacitor, mulfunction by insufficiency of the TRIAC holding current, and the abnormal oscillation by LC resonant. In this paper, we proposes the single-stage quasi-resonant PSR(Primary Side Regulation) PWM converter, and the design, the simulation and experiment are performed. As a result, it could confirm that the proposed PWM converter is the lighting equipments for LED drive which can alternate the existing 60W class incandescent bulbs and it has the high drive performance of the efficiency 80% and over, the power factor 0.95 and over under the normal voltage 220V. Finally, total harmonic distortion(THD) is gratified with a standard[1] of the lighting equipments and the durability is evaluated as the high reliablilty of 150,000 hours and over.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.1
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• pp.71-76
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• 2010

This paper is focused on implementing a real-time data acquisition system that checks power facility status by applying network based technology to Urban Transit substation power facilities and the results of its on-field tests. This system is composed of a sensor part, a measurement part, a transceiver part, a host computer, and a power source part. The system is designed to collect, save, analyze, and display the online state power facility AI (Analog Input). This system measures voltage and current from positive feeders and negative feeders where it is possible to check abnormalities of the substation‘s main power facilities. By monitoring abnormal data of the Urban Transit power facilities real-time and analyzing stored data, establishing procedures of optimized maintenance is possible.

• ETRI Journal
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• v.29 no.3
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• pp.371-380
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• 2007

This paper proposes a new automatic compensation network (ACN) for a system-on-chip (SoC) transceiver. We built a 5 GHz low noise amplifier (LNA) with an on-chip ACN using 0.18 ${\mu}m$ SiGe technology. This network is extremely useful for today's radio frequency (RF) integrated circuit devices in a complete RF transceiver environment. The network comprises an RF design-for-testability (DFT) circuit, capacitor mirror banks, and a digital signal processor. The RF DFT circuit consists of a test amplifier and RF peak detectors. The RF DFT circuit helps the network to provide DC output voltages, which makes the compensation network automatic. The proposed technique utilizes output DC voltage measurements and these measured values are translated into the LNA specifications such as input impedance, gain, and noise figure using the developed mathematical equations. The ACN automatically adjusts the performance of the 5 GHz LNA with the processor in the SoC transceiver when the LNA goes out of the normal range of operation. The ACN compensates abnormal operation due to unusual thermal variation or unusual process variation. The ACN is simple, inexpensive and suitable for a complete RF transceiver environment.