• The Transactions of the Korean Institute of Power Electronics
• /
• v.20 no.6
• /
• pp.540-549
• /
• 2015

Unintentional islanding results in safety hazards, reliability, and many other issues. Therefore, the islanding detection of a power conditioning system of a distributed generation, such as a grid-connected photovoltaic inverter, is a key function for standard compliance. Currently, many anti-islanding schemes have been examined, but existing anti-islanding schemes have poor power quality and non-detection zone issues. Therefore, this study analyzes the non-detection zone in a more deliberate manner than the existing analysis of the non-detection zone and proposes a new anti-islanding scheme, which has negligible power quality degradation and no non-detection zone. Simulation and experimental results validate that the proposed scheme shows much better performance than other existing schemes.

• Journal of the Korean Solar Energy Society
• /
• v.26 no.1
• /
• pp.91-98
• /
• 2006

Islanding phenomenon of utility-connected photovoltaic power conditioning systems(PV PCS) can cause a variety of problems and must be prevented. If the real and reactive power supplied by PV PCS are closely matched to those of load, islanding detection by passive methods becomes difficult. The active frequency drift(AFD) method, called the frequency bias method, enables islanding detection by forcing the frequency of the voltage in the islanding to drift up or down. In this paper, non-detection zone(NDZ) of AFD is analyzed for the islanding detection method of utility-connected PV PCS by the simulation software tool PSIM.

• Journal of Acupuncture Research
• /
• v.29 no.1
• /
• pp.1-8
• /
• 2012

Objectives : We investigate the characteristics of foot reflex zone acupoint of facial paralysis patients. Methods : In order to make a comparison between facial nerve paralysis patient group and non-facial paralysis group, we measured foot reflex zone acupoint detection in both group of 18 patients who were diagnosticated to facial nerve paralysis and 18 persons who were not. Results : 1. In comparing the means of the foot reflex zone, the measurements of facial nerve paralysis group is different significantly from non-facial paralysis group(p<0.05). 2. The measurement of detection of foot reflex zone acupoints, such as hypophysis(垂體), nose(鼻), cerebrum(大腦), neck(頸項), Trapezius muscle(僧帽筋), eye(眼) and ear(耳) of the facial nerve paralysis group is different significantly in comparison with non-facial paralysis group(p<0.05). But the measurement of detection of foot reflex zone acupoints, such as trigeminal nerve(三叉神經), cerebellum (小腦), kidney(腎), ureter(輸尿管) and urinary bladder(膀胱) of the facial nerve paralysis group is not defferent significantly in comparison with non-facial paralysis group(p>0.05). Conclusions : The results suggest that foot reflex zone can be used in the diagnosis and treatment of facial nerve paralysis.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.21 no.4
• /
• pp.283-289
• /
• 2016

Islanding protection of a grid-connected photovoltaic (PV) inverter is a key function for standards compliance. Unintentional islanding results in safety hazards, reliability, and many other issues. Therefore, many anti-islanding schemes have been examined. However, existing anti-islanding schemes have poor power quality and non-detection zone issues. Moreover, most schemes have problems that deteriorate the performance of islanding detection under parallel operation. Therefore, this paper proposes a novel anti-islanding scheme that has negligible power quality degradation and has no non-detection zone and islanding detection under a parallel operation. Both simulation and experimental results validate the proposed scheme.

• Proceedings of the KIPE Conference
• /
• 2016.07a
• /
• pp.351-352
• /
• 2016

Since anti-islanding scheme of grid-connected inverter is a key function of standards compliance, unintentional islanding results in safety hazards, reliability, and many other issues. Therefore, many anti-islanding schemes have been researched, however, existing anti-islanding schemes show poor power quality and non-detection zone issues. Besides, most of them have problems which deteriorate performance of islanding detection under parallel-operation. Therefore, this paper proposes a new anti-islanding scheme that has both negligible power quality degradation, no non-detection zone and precise islanding detection under parallel-operation. Finally, both simulation and experimental results validate the proposed scheme.

• Journal of Power Electronics
• /
• v.16 no.2
• /
• pp.760-768
• /
• 2016

Three-phase grid-connected inverters are widely applied in the fields of new energy power generation, electric vehicles and so on. Islanding detection is necessary to ensure the stability and safety of such systems. In this paper, feature recognition technology is applied and a novel islanding detection method is proposed. It can identify the features of inverter systems. The theoretical values of these features are defined as codebooks. The difference between the actual value of a feature and the codebook is defined as the quantizing distortion. When islanding happens, the sum of the quantizing distortions exceeds the threshold value. Thus, islanding can be detected. The non-detection zone can be avoided by choosing reasonable features. To accelerate the speed of detection and to avoid miscalculation, an active islanding detection method based on feature recognition technology is given. Compared to the active frequency or phase drift methods, the proposed active method can reduce the distortion of grid-current when the inverter works normally. The principles of the islanding detection method based on the feature recognition technology and the improved active method are both analyzed in detail. An 18 kVA DSP-based three-phase inverter with the SVPWM control strategy has been established and tested. Simulation and experimental results verify the theoretical analysis.

• 전자공학회논문지 IE
• /
• v.43 no.2
• /
• pp.63-69
• /
• 2006

Islanding phenomenon of utility-connected PV power conditioning systems(PV PCS) can cause a variety of problems and must be prevented. If the real and reactive powers supplied by PV PCS are closely matched to those of load, islanding detection by passive methods becomes difficult. The active frequency drift(AFD) method, called the frequency bias method, enables islanding detection by forcing the frequency of the voltage in the islanding to drift up or down. In this paper, non-detection zone(NDZ) of AFD is analyzed for the islanding detection method of utility-connected PV PCS by simulation tool PSIM.

• Journal of Power Electronics
• /
• v.16 no.3
• /
• pp.1141-1151
• /
• 2016

This study proposes a novel islanding detection method for distributed photovoltaic (PV) systems with multi-inverters based on a combination of the power line carrier communication and Sandia frequency shift islanding detection methods. A parameter design method is provided for the novel scheme. On the basis of the designed parameters, the effect of frequency measurement errors and grid line impedance on the islanding detection performance of PV systems is analyzed. Experimental results show that the theoretical analysis is correct and that the novel method with the designed parameters has little effect on the power quality of the inverter output current. Non-detection zones are not observed, and a high degree of reliability is achieved. Moreover, the proposed islanding detection method is suitable for distributed PV systems with multi-inverters.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.15 no.1
• /
• pp.101-106
• /
• 2020

This research is related to a development of the ultrasonic detector for an internal defect detection of various assembly part's welding zone. In this research, measurement S/Ws including system's motion control, S/W ultrasonic transmitter/receiver control, defect judgment standard setting, etc. have been designed for ultrasonic detection, and welding defects sample network, etc. were also designed for comparison between products in good condition and defective products. Through this kind of system, automatic detection function can be performed for the depth and the defect location of the assembly parts welding zone, and the system is able to make a judgment of internal defect detection which is used to be performed by an expert in the past.

• Proceedings of the KIPE Conference
• /
• 2004.07b
• /
• pp.494-497
• /
• 2004

계통연계형 태양광발전 시스템의 확대보급에 따라 단독운전 검출기법의 검출 성능에 대한 검증의 필요성이 대두되고 있다. 본 논문에서는 단독운전 검출기법의 대표적인 능동적 검출기법인 무효전력 변동기법 (reactive power variation method)과 주파수 쉬프트기법(active frequency drift method)을 IEEE Std 929-2000에서 명시된 단독운전검출 시험 방법을 이용하여 단독운전검출기법의 성능 및 불검출 영역(non-detection zone)에 대하여 비교 분석하였다.