• Asian Pacific Journal of Cancer Prevention
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• 제16권16호
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• pp.7123-7127
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• 2015

Purpose: To determine the utility of secondary circulating prostate cells for predicting early biochemical failure after radical prostatectomy for prostate cancer and compare the results with the Walz nomagram. Materials and Methods: A single centre, prospective study of men with prostate cancer treated with radical prostatectomy between 2004 and 2014 was conducted, with registration of clinical-pathological details, total serum PSA pre-surgery, Gleason score, extracapsular extension, positive surgical margins, infiltration of lymph nodes, seminal vesicles and pathological stage. Secondary circulating prostate cells were obtained using differential gel centrifugation and assessed using standard immunocytochemistry with anti-PSA. Biochemical failure was defined as a PSA >0.2ng/ml, predictive values werecalculated using the Walz nomagram and CPC detection. Results: A total of 326 men participated, with a median follow up of 5 years; 64 had biochemical failure within two years. Extracapsular extension, positive surgical margins, pathological stage, Gleason score ${\geq}8$, infiltration of seminal vesicles and lymph nodes were all associated with higher risk of biochemical failure. The discriminative value for the nomogram and circulating prostate cells was high (AUC >0.80), predictive values were higher for circulating prostate cell detection, with a negative predictive value of 99%, sensitivity of 96% and specificity of 75%. Conclusions: The nomagram had good predictive power to identify men with a high risk of biochemical failure within two years. The presence of circulating prostate cells had the same predictive power, with a higher sensitivity and negative predictive value. The presence of secondary circulating prostate cells identifies a group of men with a high risk of early biochemical failure. Those negative for secondary CPCs have a very low risk of early biochemical failure.

• 전기학회논문지
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• 제59권8호
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• pp.1374-1381
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• 2010

This paper discusses the characteristics of sheath circulating current as well as the development and application of new software for underground power cable systems. Generally, in steady state, high sheath circulating current causes the increase of sheath temperature and thermal resistance which leads to the steeply reduction of the power capacity. Therefore, the exact calculation of sheath circulating current is required for analysis about the influence of high sheath current on permissible current. In this paper, Power Cable Simulator is developed for calculation of the sheath current. It can analyse the sheath current by real time. It is also easier to use than conventional software, such as EMTP and CabSim, because all the data for calculating the cable parameters are stored in a database(DB) within Power Cable Simulator. In addition, the accuracy of Power Cable Simulator is also proved through the comparison among the current calculated by Power Cable Simulator, EMTP and Cabsim with measured current.

• Journal of Power Electronics
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• 제8권4호
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• pp.332-344
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• 2008

High frequency AC (HFAC) power distribution systems delivering power through a high frequency AC link with sinusoidal voltage have the advantages of simple structure and high efficiency. In a multiple module system, where multiple resonant inverters are paralleled to the high frequency AC bus through connection inductors, it is necessary for the output voltage phase angles of the inverters be controlled so that the circulating current among the inverters be minimized. However, the phase angle of the resonant inverters output voltage can not be controlled with conventional phase shift modulation or pulse width modulation. The phase angle is a function of both the phase of the gating signals and the impedance of the resonant tank. In this paper, we proposed a pulse phase modulation (PPM) concept for the resonant inverters, so that the phase angle of the output voltage can be regulated. The PPM can be used to minimize the circulating current between the resonant inverters. The mechanisms of the phase angle control and the PPM were explained. The small signal model of a PPM controlled half-bridge resonant inverter was analyzed. The concept was verified in a half bridge resonant inverter with a series-parallel resonant tank. An HFAC power distribution system with two resonant inverters connected in parallel to a 500kHz, 28V AC bus was presented to demonstrate the applicability of the concept in a high frequency power distribution system.

• Journal of Electrical Engineering and Technology
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• 제13권3호
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• pp.1241-1250
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• 2018

Parallel three-phase voltage source inverters in a direct connection configuration are widely used to increase system power ratings. A zero-sequence circulating current can be generated according to the switching method; however, the zero-sequence circulating current not only distorts current, but also reduces the system reliability and efficiency. In this paper, a model predictive control scheme is proposed for parallel inverters to drive an interior permanent magnet synchronous motor with zero-sequence circulating current suppression. The voltage vector of the parallel inverters is derived to predict and control the torque and stator flux components. In addition, the zero-sequence circulating current is suppressed by designing the cost function without an additional current sensor and high-impedance inductor. Simulation and experimental results are presented to verify the proposed control scheme.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 추계학술대회 논문집 학회본부
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• pp.385-387
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• 1988

Dual converter is being used as a four-quadrant source for the controlled rectifier. But the rectifier itself and circulating current between P and N-converter contribute to generate reactive power. The methodology of input power factor control of dual converter by means of circulating current control is presented in this paper.

• 한국산학기술학회논문지
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• 제21권5호
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• pp.672-678
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• 2020

교류전기철도 급전시스템에 병렬급전방식을 적용할 경우, 전동차 부하로 인한 전압강하 및 최대순시부하를 감소시켜 급전구간을 연장하고 급전용량을 향상시킬 수 있다는 장점이 있다. 그러나 변전소 간에 위상차가 있을 경우 순환전력이 발생하기 때문에 적용이 제한되며, 전동차 운행에 따른 부하 분포에 따라 변전소 부하 불균형이 커져서 급전용량이 저하되는 문제점이 있다. 본 논문에서는 변전소 위상차 및 전동차 부하분포에 따라 변동하는 순환전력을 실시간 제어하고 변전소 부하 불균형을 해소하기 위하여 사이리스터 제어 위상조정장치 (TCPAR: Thyristor Controlled Phase Angle Regulator, 이하 TCPAR)를 적용하는 방식을 제안하고, 이를 구현하기 위한 검토를 수행하였다. 전기철도 급전 시스템에 TCPAR을 적용하기 위한 제어 기법으로서, 변전소 공급전력을 입력으로 이용하여 변전소 위상차 및 전동차 부하 분포에 따라 변동하는 순환전력과 변전소 부하 불균형을 효과적으로 억제하는 제어모델을 제시하였다. PSCAD/EMTDC를 이용한 시뮬레이션 결과, 전기철도 병렬급전에 제안한 TCPAR을 적용함으로써 변전소 위상차 및 전동차 부하분포에 따라 변동하는 순환전력 및 변전소 부하 불균형을 효과적으로 억제시킬 수 있다는 것을 확인하였다. 제안 기법을 전기철도 병렬급전에 적용할 경우, 병렬급전 적용 범위를 확대하고 급전용량을 증가시킬 수 있을 것으로 기대된다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.189-191
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• 2018

This paper introduces a novel ZVS interleaved totem-pole PFC with the reduced circulating current and the reverse recovery current of the diodes. With the help of a simple auxiliary inductor, both ZVS turn-on of the main switches and soft turn-off of the body diodes can be achieved. In the proposed totem-pole PFC topology since the switching losses and the reverse recovery losses can be significantly reduced, the typical Si MOSFETs can be employed. In addition the circulating current is reduced by adjusting the switching frequency. The proposed PFC topology can be a low cost solution to achieve high efficiency in high power PFC applications. The validity and the feasibility of the proposed topology is verified by the experimental results with a 3.3kW interleaved totem-pole PFC converter.

• Journal of Power Electronics
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• 제15권3호
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• pp.652-659
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• 2015

This paper presents a new hybrid soft switching dc-dc converter with a low circulating current and high circuit efficiency. The proposed hybrid converter includes two sub-converters sharing two power switches. One is a three-level PWM converter and the other is a LLC converter. The LLC converter and the three-level converter share the lagging-leg switches and extend the zero-voltage switching (ZVS) range of the lagging-leg switches from nearly zero to full load since the LLC converter can be operated at f_sw (switching frequency) $\approx$ f_r (series resonant frequency). A passive snubber is used on the secondary side of the three-level converter to decrease the circulating current on the primary side, especially at high input voltage and full load conditions. Thus, the conduction losses due to the circulating current are reduced. The output sides of the two converters are connected in series. Energy can be transferred from the input voltage to the output load within the whole switching period. Finally, the effectiveness of the proposed converter is verified by experiments with a 1.44kW prototype circuit.

• Journal of Power Electronics
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• 제15권6호
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• pp.1429-1437
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• 2015

A new parallel hybrid soft switching converter with low circulating current losses during the freewheeling state and a low output current ripple is presented in this paper. Two circuit modules are connected in parallel using the interleaved pulse-width modulation scheme to provide more power to the output load and to reduce the output current ripple. Each circuit module includes a three-level converter and a half-bridge converter sharing the same lagging-leg switches. A resonant capacitor is adopted on the primary side of the three-level converter to reduce the circulating current to zero in the freewheeling state. Thus, the high circulating current loss in conventional three-level converters is alleviated. A half-bridge converter is adopted to extend the ZVS range. Therefore, the lagging-leg switches can be turned on under zero voltage switching from light load to full load conditions. The secondary windings of the two converters are connected in series so that the rectified voltage is positive instead of zero during the freewheeling interval. Hence, the output inductance of the three-level converter can be reduced. The circuit configuration, operation principles and circuit characteristics are presented in detail. Experiments based on a 1920W prototype are provided to verify the effectiveness of the proposed converter.

• 플랜트 저널
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• 제8권1호
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• pp.73-80
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• 2012

The structure and combustion characteristics, and the economic feasibility of the circulating fluidized bed combustion(CFBC) boiler using low grade coal were introduced. The economic feasibility is evaluated by comparing a 500 MW CFBC boiler power plant using low grade coal and a pulverized combustion boiler power plant with high grade coal. As the result of the evaluation, the pulverized coal combustion boiler power plant has an internal rate of return of 12.95%, 1,395.9 billion Korean won of net present value, and 6.26 years of payback period. On the other hand, CFBC boiler power plant has an internal rate of return of 13.54%, 1,704.3 billion Korean won of net present value, and 6.02 years payback period. Therefore, the CFBC boiler power plant has better feasibility in all aspects, as 0.59% higher of internal rate of return, 308.4 billion Korean won of higher net present value and 0.24 year of shorter payback period.