• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.817-825
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• 2017

The AC-common bus microgrid system can overcome several weaknesses of the DC microgrid system by interconnecting the DC/AC inverters used for renewable energy with an AC network. Nevertheless, the unbalanced loads inherent in the electric power systems of island and small communities can deteriorate the performance of the AC microgrid system. This is because of the limited voltage regulation capability and mixed power flow in the voltage source inverter. In order to overcome the unbalanced load condition, this paper proposes a voltage and current control algorithm for the 4-leg inverter based on the single phase d-q control method, as well as the modeling of the voltage controller using Matlab/Simulink S/W. From the S/W simulation and experiment of the 250KW proto-type inverter, it is confirmed that the proposed algorithm is a useful tool for the design and operation of the AC microgrid system.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.493-500
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• 2017

Based on the data accumulated through EMU fault management, this paper examines the reliability of old railway car parts and proposes measurements to improve safety. Subway Line 7 of the Seoul Metropolitan Rapid Transit Corporation, auxiliary power unit (Static Inverter) of the EMU second version is a core equipment to supply power to various room-service units in cars and make an effect directly on passenger satisfaction. To analyze the pattern of failure throughout the field data over a long period of time, this analysis of statistics and reliability considers the operating environment and stress factors. This statistical analysis presents the correlation between failure and the temperature stress factors related to frequent failure occurring intensively in summer. In addition, throughout the analysis of the life of the IGBT inverter, the effect of the temperature stress factor was observed before and after the repair. As a result of an analysis of the optimal operating conditions considering two variations of EMU, such as variable load and outside temperature, a difference in the cooling capacity between the optimal operating conditions and frequent failure conditions was observed. Based on this analysis, this paper suggests a way to minimize cooling capacity difference for the optimal operational conditions.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.1
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• pp.70-79
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• 2003

In this paper, T5 28-watt fluorescent lamp ballast using a piezoelectric transformer is fabricated and its characteristic is investigated. Developed electronic ballast is composed of basic circuits and blocks, such as rectifier part, active power factor corrector part, frequency oscillation part using microcontroller and feedback control, piezoelectric transformer and resonant half bridge inverters. The fabricated ballast uses to variable frequency methode in external so exciting that the frequency of piezoelectric transformer could be generated by voltage control oscillator using microcontroller(AT90S4433). The current of fluorescent lamp is detected by feedback control circuit. The signal of inverter output is received using Piezoelectric transformer, and then its output transmitted to fluorescent lamp. Traditional electromagnetic ballasts operated at 50-60Hz have been suffered from noticeable flicker, high loss, large crest factor and heavy weight. A new electronic ballast is operated at high frequency about 75kHz, and then Input power factor, distortion of total harmonic and lamp current crest factor are measured about 0.9!35, 12H and 1.5, respectively Accordingly, the traditional ballast is by fabricated electronic ballast using piezoelectric transformer and voltage control oscillator because of its lighter weight, high efficiency, economic merit and saving energy.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.3
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• pp.401-417
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• 1994

In this paper, a new testable design technique for domino CMOS circuits is proposed to detect stuck-at(s-at), stuck-open(s-op) and stuck-on(s-on) faults in the circuits by observing logic test reponses. The proposed technique adds one pMOS transistor per domino CMOS gate for s-op and s-on faults testing of nMOS transistors and one nMOS transistors and one nMOS transistor per domino gate or multilevel circuit to detect s-on faults in pMOS transistors of inverters in the circuit. The extra transistors enable the proposed testable circuit to operate like a pseudo static nMOS circuit while testing nMOS transistors in domino CMOS circuits. Therefore, the two=phase operation of a precharge phase and a evaluation phase is not needed to keep the domino CMOS circuit from malfunctionong due to circuit delays in the test mode, which reduces the testing time and the complexity of test generation. Most faults of th transistors in the proposed testable domino CMOS circuit can be detected by single test patterns. The use of single test patterns makes the testing of the proposed testable domino CMOS circuit free from path delays, timing skews, chage sharing and glitches. In the proposed design, the testing of the faults which, require test sequences also becomes free from test invalidation. The conventional automatic test pattern generators(ATPG) can be used for generating test patterns to detect faults in the circuits.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.47 no.2
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• pp.25-34
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• 2010

This paper proposed a high-speed voltage-controlled ring-oscillator(VCRO) using a frequency doubling technique. The design of the proposed oscillator has been based on TSMC 0.18um 1.8V CMOS technology. The frequency doubling technique is achieved by AND-OR operations with 4 signals which have $90^{\circ}$ phase difference one another in one cycle. The proposed technique has been implemented using a 4-stage differential oscillator compose of differential latched inverters and NAND gates for AND and OR operations. The differential ring-oscillator can generate 4 output signals, which are $90^{\circ}$ out-of-phase one another, with low phase noise. The ANP-OR operations needed in the proposed technique are implemented using NAND gates, which is more area-efficient and provides faster switching speed than using NOR gates. Simulation results show that the proposed, VCRO operates in the frequency range of 3.72 GHz to 8 GHz with power consumption of 4.7mW at 4GHz and phase noise of ~-86.79dBc/Hz at 1MHz offset. Therefore, the proposed oscillator demonstrates superior performance compared with previous high-speed voltage-controlled ring-oscillators and can be used to build high-performance frequency synthesizers and phase-locked loops for radio-frequency applications.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.47 no.3
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• pp.7-17
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• 2010

In this paper, an innovative low-power SRAM based on 4-transistor latch cell is described. The memory cells are composed of two cross-coupled inverters without access transistors. The sources of PMOS transistors are connected to bitlines while the sources of NMOS transistors are connected to wordlines. They are accessed by totally new read and write method which results in low operating power dissipation in the nature. Moreover, the design reduces the leakage current in the memory cells. The proposed SRAM has been demonstrated through 16-kbit test chip fabricated in a 0.18-${\mu}m$ CMOS process. It shows 17.5 ns access at 1.8-V supply while consuming dynamic power of $87.6\;{\mu}W/MHz$ (for read cycle) and $70.2\;{\mu}W/MHz$ (for write cycle). Compared with those of the conventional 6-transistor SRAM, it exhibits the power reduction of 30 % (read) and 42 % (write) respectively. Silicon measurement also confirms that the proposed SRAM achieves nearly 64 % reduction in the total standby power dissipation. This novel SRAM might be effective in realizing low-power embedded memory in future mobile applications.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.3
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• pp.486-495
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• 2006

In this paper, a low-power 1Kb synchronous EEPROM is designed with flash cells for passive UHF RFID tag chips. To make a low-power EEPROM, four techniques are newly proposed. Firstly, dual power supply voltages VDD(1.5V) and VDDP(2.5V), are used. Secondly, CKE signal is used to remove switching current due to clocking of synchronous circuits. Thirdly, a low-speed but low-power sensing scheme using clocked inverters is used instead of the conventional current sensing method. Lastly, the low-voltage, VDD for the reference voltage generator is supplied by using the Voltage-up converter in write cycle. An EEPROM is fabricated with the $0.25{\mu}m$ EEPROM process. Simulation results show that power dissipations are $4.25{\mu}W$ in the read cycle and $25{\mu}W$ in the write cycle, respectively. The layout area is $646.3\times657.68{\mu}m^2$.

• Journal of Radiation Industry
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• v.6 no.1
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• pp.31-40
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• 2012

There are two methods to fabricate the readout electronic to a large-area CMOS image sensor (LACIS). One is to design and manufacture the sensor part and signal processing electronics in a single chip and the other is to integrate both parts with bump bonding or wire bonding after manufacturing both parts separately. The latter method has an advantage of the high yield because the optimized and specialized fabrication process can be chosen in designing and manufacturing each part. In this paper, LACIS chip, that is optimized design for the latter method of fabrication, is presented. The LACIS chip consists of a 3-TR pixel photodiode array, row driver (or called as a gate driver) circuit, and bonding pads to the external readout ICs. Among 4 types of the photodiode structure available in a standard CMOS process, $N_{photo}/P_{epi}$ type photodiode showed the highest quantum efficiency in the simulation study, though it requires one additional mask to control the doping concentration of $N_{photo}$ layer. The optimized channel widths and lengths of 3 pixel transistors are also determined by simulation. The select transistor is not significantly affected by channel length and width. But source follower transistor is strongly influenced by length and width. In row driver, to reduce signal time delay by high capacitance at output node, three stage inverter drivers are used. And channel width of the inverter driver increases gradually in each step. The sensor has very long metal wire that is about 170 mm. The repeater consisted of inverters is applied proper amount of pixel rows. It can help to reduce the long metal-line delay.

• Journal of the Korean Solar Energy Society
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• v.39 no.1
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• pp.59-66
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• 2019

BIPV or BAPV installation applied to building is increasing through public utility mandates enterprise. Solar PV energy generates only during the day, but if it is operated in convergence with ESS, which stores electrical energy, it can restrain the fossil energy used in buildings throughout the day. A solution is to converge with PV system and ESS. However, PV systems and ESS connected to the power grid in parallel can cause problems of electrical stability. A study was conducted on the case of failure to detect islanding operation under the parallel operation of PV generation and ESS that are connected in parallel to power grid. Experiments conducted various non-islanding detections under the operating conditions. In the experiment results, when one PCS - PV inverter or ESS inverter - was operating under the islanding condition, it stopped working within 0.5 seconds of the Korean grid standard. However, when both of PV inverter and ESS inverter were operating at the same time under the islanding situation, the anti-islanding algorithm did not operate normally and both inverters continuously supplied power to the connected RLC loads. islanding detection Algorithm developed by each inverter manufacturer has caused this phenomenon. Therefore, this paper presented a new test standard for islanding detection.

• Journal of Advanced Navigation Technology
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• v.24 no.6
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• pp.620-626
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• 2020

This research propose and simulate a solar power generation system monitoring system based on Modbus TCP communication using RaspberryPi, an IOT equipment, as a master and an inverter as a slave. In this model, various sensors are added to the RaspberryPi to add necessary information for monitoring solar power plants, and power generation prediction and monitoring information are transmitted to the smart phone through real-time power generation prediction. In addition, information that is continuously generated by the solar power plant is built on the server as big data, and a deep learning model for predicting power generation is trained and updated. As a result of the study, stable communication was possible based on Modbus TCP with the Raspberry Pi in the inverter, and real-time prediction was possible with the deep learning model learned in the Raspberry Pi. The server was able to train various deep learning models with big data, and it was confirmed that LSTM showed the best error with a learning error of 0.0069, a test error of 0.0075, and an RMSE of 0.0866. This model suggested that it is possible to implement a real-time monitoring system that is simpler, more convenient, and can predict the amount of power generation for inverters of various manufacturers.