• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.2
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• pp.131-137
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• 1998

The solar cells should be operated at the maximum power point because its output characteristics are greatly fluctuated on the variation of insolation, temperature and load. Photovoltaic system needs an inverter which can interface the dc output power of solar cell with the residential ac load. The inverter has to supply a sinusoidal current and voltage to the load and the utility line with a high power factor. This paper proposes an utility interactive photovoltaic system designed with a step-up chopper and a PWM voltage source inverter. The step-up chopper operates in continuous mode by adjusting the duty ratio so that the photovoltaic system tracks the maximum power points of solar cell without any influence on the variation of insolation and temperature. The voltage source inverter operates in a manner that its output voltage is in phase with the utility voltage. The inverter supplies an ac power with high factor and low level of harmonics to the load and the utility power system.

• Proceedings of the KIEE Conference
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• 2000.07a
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• pp.28-30
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• 2000

This paper introduces a power flow model of SSSC for voltage stability study. The SSSC model is obtained from the injection model of voltage source inverter by adding the condition that SSSC injection voltage is in quadrature with current of SSSC-installed branch. This model is incorporated into modified CPF algorithm to study effects of SSSC on the security-constrained interface flow limit. Determination of interface flow limit is simply briefed. In case study a 771-bus real system is used to show that SSSC can improve interface flow limit in terms of voltage stability.

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.325-329
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• 2002

This paper is intended as an investigation of the interface between Neutral section insulators and pantograph interface. Neutral section insulators are installed at the boundary between AC catenary system and DC catenary system, which should provide electrical insolation between two different catenary systems and pass the trains without interruption. As the number of the pantographs installed on the train increased, which is necessary for the VVVF inverter drive trains introduced in recent years, there occurs an serious aspects of the interaction between pantographs and Neutral section insulators. These effects hinder the automatic switch operation of MCB(Main Circuit Breaker) after passing through the section insulators, and lead to the extra-ordinary wear of FRP insulator material of section insulators. Countermeasures in terms of the interface between the Neutral secton insulators and electric collection system of train are provided too.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.620-621
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• 2008

Transparent electronics has been one of the key terminologies forecasting the ubiquitous technology era. Several researchers have thus extensively developed transparent oxide-based thin-film transistors (TFTs) on glass and plastic substrates although in general high voltage operating devices have been mainly studied considering transparent display drivers. However, low voltage operating oxide TFTs with transparent electrodes are very necessary if we are aiming at logic circuit applications, for which transparent complementary or one-type channel inverters are required. The most effective and low power consuming inverter should be a form of complementary p-channel and n-channel transistors but real application of those complementary TFT inverters also requires electrical- and even photo-stabilities. Since p-type oxide TFTs have not been developed yet, we previously adopted organic pentacene TFTs for the p-channel while ZnO TFTs were chosen for n-channel on sputter-deposited $AlO_x$ film. As a result, decent inverting behavior was achieved but some electrical gate instability was unavoidable at the ZnO/$AlO_x$ channel interface. Here, considering such gate instability issues we have designed a unique transparent complementary TFT (CTFTs) inverter structure with top n-ZnO channel and bottom p-pentacene channel based on 12 nm-thin nano-oxide/self assembled monolayer laminated dielectric, which has a large dielectric strength comparable to that of thin film amorphous $Al_2O_3$. Our transparent CTFT inverter well operate under 3 V, demonstrating a maximum voltage gain of ~20, good electrical and even photoelectric stabilities. The device transmittance was over 60 % and this type of transparent inverter has never been reported, to the best of our limited knowledge.

• Journal of Institute of Control, Robotics and Systems
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• v.9 no.4
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• pp.340-346
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• 2003

Driven by the growth of the Internet and the increasing ubiquity of embedded computing systems, the embedded system is exploding in terms of it proliferation of products and the number of complex applications. Intelligent dedicated systems and appliances used in interface, monitoring, communications, and control applications increasingly demand the services of a sophisticated, state-of-the-art operating system. In the case of industrial controller, it is required to use a real-time operating system (RTOS) as a good building block to enable Internet connectivity. However, commercial RTOSes are increasingly less desirable due to their lack of standardization and their inability to keep pace with the rapid evolution of technology. In order to overcome these problems, we consider using embedded Linux and embedded web server. Availability of source code, reduced licensing, reliability, open source community support, as well as others, are key reasons for the use of embedded linux by embedded developers. In this paper, we develop embedded linux platform to control the industrial inverter with the Internet connecting feature. The method of web-based management is also proposed by using the embedded web server and Java applet. We show the feasibility of remote management for the commercial inverter controller with the proposed three-tier web-based remote management system.

• Journal of Power Electronics
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• v.15 no.5
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• pp.1329-1337
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• 2015

By placing distributed generation power sources beside a big nonlinear load, these sources can be used as a power quality enhancer, while injecting some active power to the network. In this paper, a new scheme to use the distributed generation power source in both operation modes is presented. In this scheme, a fuzzy controller is added to adjust the optimal set point of inverter between compensating mode and maximum active power injection mode, which works based on the harmonic content of the nonlinear load. As the high order current harmonics can be easily rejected using passive filters, the DG is used to compensate the low order harmonics of the load current. Multilevel transformerless cascade inverters are preferred in such utilization, as they have more flexibility in current/voltage waveform. The proposed scheme is simulated in MATLAB/SIMULINK to evaluate the circuit performance. Then, a 1kw single phase prototype of the circuit is used for experimental evaluation of the paper. Both simulative and experimental results prove that such a circuit can inject a well-controlled current with desired harmonics and THD, while having a smaller switching frequency and better efficiency, related to previous 3-phase inverter schemes in the literature.

• Proceedings of the KIEE Conference
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• 1992.07b
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• pp.1035-1037
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• 1992

Generally, fuel cell has characteristics of low voltage, large current and voltage variation under load change. Therefore, DC output voltage of fuel cell is too low to convert into AC with high efficiency and good performance. For this reason, fuel cell generating system is composed of DC-DC converter and inverter in cascade. This paper used 2-phase boost DC-DC converter to obtain low distortion waveform and reduce input-output current ripple, and discussed inverter which can be operated in independent drive mode and utility line interface drive mode. Then, the change of modes can be achived smoothly.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.280-282
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• 2005

Micro-source units having power ratings in thousands of watts can provide even higher reliability and fuel efficiency than the conventional large scale units. These units are also clustered with loads creating micro-grid services to customer sites such as office buildings, industrial parks and homes. Micro-sources adopt voltage source inverter to ensure the power quality of sensitive loads. This paper deals with the connection of micro-sources into the system grid. Modeling and simulation of the grid connected micro-sources at the power frequency range are investigated. Simulation results show that the micro-grid system with two micro-sources has good dynamic characteristics.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.60 no.1
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• pp.48-52
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• 2011

Over the years, traditionally, six-switch three-phase inverters have been widely utilized for variable speed alternating current motor drives. Recently, some efforts have been made on the application of four-switch three phase inverter for uninterruptible power supply and variable speed drives. This is due to some advantages of the four-switch three phase inverter over the conventional six-switch three-phase inverters such as reduced price due to reduction in number of switches, reduced switching losses, reduced number of interface circuits to supply logic signals for the switches, simpler control algorithms to generate logic signals, less chances of destroying the switches due to lesser interaction among switches, and less real-time computational burden. However such as slow di/dt and speed limitation, are the inherent characteristics and main drawbacks of the four-switch configuration. Those problems can be overcome in conjugation with Voltage-doublers which has additional advantage, such as unity power factor correction.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.313-316
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• 2002

A SRM inverter has very low switching frequency. This results in reducing the burden for a high-speed of the gate-amp interface circuit. and the linearity of optocoupler is used to protect the intanteneous peak current for the stable operation In this paper, series resistor is used to equal the current sharing of each switching device and a linear gate-amp is proposed to protect the intanteneous peak current which occurs in transient state.