• Journal of Power Electronics
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• v.16 no.3
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• pp.1176-1189
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• 2016

In this paper, a novel quasi-direct power control (Q-DPC) scheme based on a resonant frequency adaptive proportional-resonant (PR) current controller with a variable frequency resonant phase locked loop (RPLL) is proposed, which can achieve a fast power response with a unity power factor. It can also adapt to variations of the generator frequency in T-type Three-level shaft synchronous generator (SSG) converters. The PR controller under the static α-β frame is designed to track ac signals and to avert the strong cross coupling under the rotating d-q frame. The fundamental frequency can be precisely acquired by a RPLL from the generator terminal voltage which is distorted by harmonics. Thus, the resonant frequency of the PR controller can be confirmed exactly with optimized performance. Based on an instantaneous power balance, the load power feed-forward is added to the power command to improve the anti-disturbance performance of the dc-link. Simulations based on MATLAB/Simulink and experimental results obtained from a 75kW prototype validate the correctness and effectiveness of the proposed control scheme.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.614-615
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• 2007

There are roughly a hundred types of cables in power plants. The distribution of circuits in a nuclear plant is comprised of 20% instrument cables, 61% control cables, 13% AC power cables, 1% DC power cables, and 5% communication lines. In the nuclear power plant, medium voltage cables are generally included in the scope of systems reviewed for safety and are included in a plant's maintenance program. Medium voltage cables provide power to many critical components in plants, including feed water pumps, circulating water pumps, and condensate pumps. Among these cables, high temperature sections of cables feeding electrical power to the circulating water pump and the condenser extraction pump were found. The evaluation for these cables is performed to find the maximum allowable current and temperature. The result shows that the load current flowed about 85% of the allowable current ampacity, and the temperature of conductor at full load current did not exceed the limited temperature. Therefore, existing cables for circulating water pump and condenser extraction pump system are going to be used during design life.

• Journal of Electrical Engineering and Technology
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• v.9 no.2
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• pp.569-575
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• 2014

A highly efficient class E power amplifier is demonstrated for application to wireless power transfer system. The amplifier is designed with an L-type matching at the output for harmonic rejection and output matching. The power loss and the effect of each component in the amplifier with the matching circuit are analyzed with the current ratio transmitted to the output load. Inductors with a quality factor of more than 120 are used in a dc feed and the matching circuit to improve transmission efficiency. The single-ended amplifier with 20 V supply voltage shows 7.7 W output power and 90.8% power added efficiency at 6.78 MHz. The wireless power transfer (WPT) system with the amplifier shows 5.4 W transmitted power and 82.3% overall efficiency. The analysis and measurements show that high-Q inductors are required for the amplifier design to realize highly efficient WPT system.

• Journal of Power Electronics
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• v.15 no.4
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• pp.939-950
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• 2015

A single-stage AC-AC converter has been designed for a wind energy conversion system (WECS) that eliminates multistage operation and DC-link filter elements, thus resolving size, weight, and reliability issues. A simple switching strategy is used to control the switches that changes the variable-frequency AC output of an electrical generator to a constant-frequency supply to feed into a distributed electrical load/grid. In addition, a modified random sinusoidal pulse width modulation (RSPWM) technique has been developed for the designed converter to make the overall system more efficient by increasing generating power capacity and reducing the effects of inter-harmonics and sub-harmonics generated in the WECS. The technique uses carrier and reference waves of variable switching frequency to calculate the firing angles of the switches of the converter so that the three-phase output voltage of the converter is very close to a sine wave with reduced THD. A comparison of the performance of the proposed RSPWM technique with the conventional SPWM demonstrated that the power generated by a turbine in the proposed approximately increased by 5% to 10% and THD reduces by 40% both in voltage and current with respect to conventional SPWM.

• Journal of Power Electronics
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• v.17 no.4
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• pp.1117-1126
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• 2017

The main contribution of this paper is the use of sensorless active diodes to generate the gate signals for a three-phase boost-rectifier with a self-powered control scheme. The sensorless operation is achieved making use of the gate control signals generated by the active diode schemes on each of the switching devices using a pulse width half-controlled boost rectifier modulation technique (PWM-HCBR). The proposed scheme synchronizes the gate control signals with a three phase voltage supply. Autonomous operation is obtained making use of the output DC bus to feed the control circuitry, the active diodes and the driver circuitry. The three-phase boost-rectifier is supplied by a three-phase permanent magnet electric generator powered by a solar concentrator dish with variable voltage and variable frequency conditions. Experimental results report an efficiency of up to 94.6% for 25 W and an input of 3.6 V peak per phase with 450.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.71-73
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• 2019

The output current of the Grid Connected Inverter (GCI) can be polluted with harmonics mainly due to i) dead time in switches, ii) non-linearity of switches, iii) grid harmonics, and iv) DC link fluctuation. Therefore, it is essential to design the robust Harmonic Compensation (HC) technique for the improvement of output current quality and fulfill the IEEE 1547 Total harmonics Distortion (THD) limit i.e. <5%. The conventional harmonic techniques often are complex in implementation due to their i) additional hardware needs, ii) complex structure, iii) difficulty in tuning of parameters, iv) current controller compatibility issues, and v) higher computational burden. In this paper, to eliminate the harmonics from the GCI output current, a novel Digital Lock-In Amplifier (DLA) based harmonic detection is proposed. The advantage of DLA is that it extracts the harmonic information accurately, which is further compensated by means of PI controller in feed forward manner. Moreover, the proposed HC method does not require additional hardware and it works with any current controller reference frame. To show the effectiveness of the proposed HC method a 5kW GCI prototype built in laboratory. The output current THD is achieved less than 5% even with 10% load, which is verified by simulation and experiment.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.7 s.98
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• pp.671-680
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• 2005

The CFL linearisation chip which is one of key devices in ultra-narrowband mobile radio transmitter using CQPSK digital modulation method is designed and implemented with $0.35{\mu}m$ CMOS technology. The reduced size and low cost of transmitter are available by the use of direct-conversion and CFL ASIC chip, which improve the power effi챠ency and linearity of transmitting path. In addition, low power operation is possible through CMOS technology The performance test results of transmitter show -25 dBc improvement of IMD level at the 3 kHz frequency offset and then satisfy FCC 47 CFR 90.210 E emission mask in the operation of CFL ASIC chip. At that time, the transmitting power is about PEP(Peak-to-Envelope Power) 5 W. The main parameters to improve the transmitting characteristic and to compensate the distortion in feed back loop such as DC-offset, loop gain and phase value are interfaced with notebook PC to be controlled with S/W.

• Journal of the Korean Society of Food Science and Nutrition
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• v.31 no.5
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• pp.840-846
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• 2002

Male Sprague-Bawler rats were blocked into four groups which were normal rats fed control diet (NC) diabetic rats fed control diet (DC), normal rats fed Hamcho powder diet (NH), and diabetic rats fed Hamcho powder diet (DH). Diabetes was induced by single injection of streptozotocin (60 mg/kg B.W. i.p.). The animals were fed ad libitum for 5 weeks. Malondialdehyde (MDA), glucose 6-phosphtase (Gspase), glutathione S-transferase (GST) glutathione Peroxidase (GPx), and glutathione reductase (GR) activities were measured in the homogenates of liver and kidney, and total lipid, total cholesterol, triglyceride, and HDL-cholesterol concentrations in the blood serum. Food and water intakes were markedly higher in diabetic groups than those of normal groups and were not significantly decreased by Hamcho powder supplementation, But, FER (Feed efficiency ratio) of DH Brood was higher than that of U group. Total cholesterol level of DH group was decreased in the second and third week, and the weekly change of blood sugar was also decreased in the 5th week. Dietary Hamcho intake showed 41.2% of hypoglycemic effect in diabetics rats. Levels of total lipid and triglycerides of DH group were lower than those of DC group. Hepatic GR activity of DH group was higher than those of other groups. However, renal GR activity was lower than those of other groups. Hepatic G6Pase activity was significantly high in DH group and reduced by Hamcho powder supplementation. GST was reduced by Hancho diet in diabetic rats. In conclusion Hamcho supplementation decreased serum lipid and glucose concentration in STZ-induced diabetic rats and this effects of Hamcho might exert antidiabetic effect of Hamcho powder diet.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.5
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• pp.492-501
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• 2013

In this paper, a multi polarization reconfigurable microstrip antenna that can be used selectively for four polarizations(vertical polarization, horizontal polarization, right hand circular polarization, left hand circular polarization) at the S-band is presented. The proposed antenna consists of four PIN diodes and a microstrip patch with a cross slot and a circular slot and is fed by utiliting electromagnetic coupling between the microstrip patch and the feed line. The proposed antenna has a DC bias network to supply DC voltage to each PIN diode and the polarization can be determined by controlling the ON /OFF states of four PIN diodes. The fabricated antenna has a VSWR below 2 in the vertical polarization(3.17~3.21 GHz), the horizontal polarization(3.16~3.20 GHz), the left hand circular polarization (3.08~3.19 GHz), and the right hand circular polarization(3.10~3.2 GHz) frequency bands. The designed antenna has the cross polarization level higher than 20 dB, a gain over 5 dBi for the linear polarization states, and 3 dB axial ratio bandwidth wider than 50 MHz in the circular polarization states.

• Journal of the Korean Society of Food Science and Nutrition
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• v.16 no.2
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• pp.98-104
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• 1987

Studies were carried out to determined the optimal conditions of processing and changes in trypsin indigestible substrate(TIS) and in vitro protein digestibility of paddy grasshopper(Oxya chinensis formosana) under various drying conditions. The multienzyme assy and amino acid compositions were used to predict the quality changes of dried products. The in vitro protein digestidility of defatted products were higher than that of sun and hot air dried products. This results indicated that heat processing is decreased the digestibility, but is increased the TIS contents of dried samples. Amino acid composition of the products was comparable to the ANRC casein scoring pattern. The protein was espeoially low in the amount of lysine, tryptophan and methionine, but high in the quantity of aspartic acid, glutamic acid and arginine indicating that it could be a difference of the dry processing. C-PER and DC-PER were 2.65 and 2.44, respectively, in the defatted and freeze dried products and 2.49 and 2.30, respectively, in hot air dried products. From the these results, it could be confirmed that defatted and freeze dried products might be utilized with feed or foodstuff, unless the toxic substances were no longer detectable.