• Journal of Power Electronics
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• 제11권4호
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• pp.576-582
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• 2011

This paper presents a novel control strategy for selective compensation of power quality (PQ) problems, depending upon the limited rating of voltage source inverters (VSIs), through a unified power quality conditioner (UPQC) in a three-phase four-wire distribution system. The UPQC is realized by the integration of series and shunt active power filters (APFs) sharing a common dc bus capacitor. The shunt APF is realized using a three-phase, four-leg voltage source inverter (VSI), while a three-leg VSI is employed for the series APF of the three-phase four-wire UPQC. The proposed control scheme for the shunt APF, decomposes the load current into harmonic components generated by consumer and distorted utility. In addition to this, the positive and negative sequence fundamental frequency active components, the reactive components and harmonic components of load currents are decomposed in synchronous reference frame (SRF). The control scheme of the shunt APF performs with priority based schemes, which respects the limited rating of the VSI. For voltage harmonic mitigation, a control scheme based on SRF theory is employed for the series APF of the UPQC. The performance of the proposed control scheme of the UPQC is validated through simulations using MATLAB software with its Simulink and Power System Block set toolboxes.

• Journal of Power Electronics
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• 제18권1호
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• pp.116-128
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• 2018

Conventionally, in order to reduce the ac components of the dc-link capacitors of the two-level Half-Bridge Voltage Source Inverter (HB-VSI), high dc-link capacitances are required. This necessitates the employment of short-lifetime and bulky electrolytic capacitors. In this paper, an analysis for the performance of low dc-link capacitances-based HB-VSI is presented to elucidate its ability to generate an enhanced fundamental output voltage magnitude without increasing the voltage rating of the involved switches. This feature is constrained by the load displacement factor. The introduced enhancement is due to the ac components of the capacitors' voltages. The presented approach can be employed for multi-phase systems through using multi single-phase HB-VSI(s). Mathematical analysis of the proposed approach is presented in this paper. To ensure a successful operation of the proposed approach, a closed loop current controller is examined. An expression for the critical dc-link capacitance, which is the lowest dc-link capacitance that can be employed for unipolar capacitors' voltages, is derived. Finally, simulation and experimental results are presented to validate the proposed claims.

• Journal of Power Electronics
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• 제18권6호
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• pp.1844-1854
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• 2018

Isolated power systems (IPS) are often characterized by a weak grid due to small power grids. The grid side voltage is no longer equivalent to an ideal voltage source of an infinitely big power grid. The conversion control of new energy sources, parameter perturbations as well as the load itself can easily cause the system voltage to oscillate or to become unstable. To solve this problem, increasing the energy-storage power sources is usually used to improve the reliability of a system. In order to provide support for the voltage, the energy-storage power source inverter needs an method to control the voltage source. Therefore, this paper has proposed the active damping control of a voltage source inverter (VSI) based on virtual compensation. By simplifying the VSI double closed-loop control, two feedback compensation channels have been constructed to reduce the VSI output impedance without changing the characteristics of the voltage gain of a system. This improvement allows systems to operate stably in a larger range. A frequency-domain analysis, and simulation and experimental results demonstrate the feasibility and effectiveness of the proposed method.

• 한국학교ㆍ지역보건교육학회지
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• 제10권2호
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• pp.1-13
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• 2009

Objectives: This study is a quasi-experimental research with nonequivalent control group pretest-posttest design study to compare and verify the educational effects between CPR Song.Video Self-Instruction and CPR VSI. Method: We selected total 58 subjects who were freshmen at the Dept of Emergency Medical technology, G College in G Metropolitan City and 28 of them were experimental group which had no experience to have CPR instruction and consented to take part in this research and 30 students were control group. Data were collected from Apr. 27 to 29, 2009. Data were analyzed with SPSS/PC+(version 14.0). and all significance level was set as p<0.05. Results: 1. In the knowledge of CPR, the knowledge level before CPR instruction was 2.17 out of 10 in experimental group and 1.86 in control group. After CPR instruction, experimental group got 9.07 and it meant the increase of 6.89 and control group showed increase to 7.16(p=0.000). 2. Self-efficacy of CPR showed 2.61 out of 10 in both experimental and control groups, and after CPR instruction, experimental group showed increase of 3.93 as 6.55 and control group showed increase of 3.91 as 6.52(p=0.000). 3. Accuracy of CPR performance was 0.32 out of 10 in experimental group and 0.40 in control group. After CPR instruction, experimental group got 9.25 and showed increase of 8.92 and control group got 9.20 and showed increase of 8.80(p=0.000). 4. Study satisfaction was 4.22 out of 5 in experimental group and 3.04 in control group, and experimental group was higher than control group. there was no statistically significant difference. Conclusions: This study found that CPR Song；Video Self-Instruction achieved better results than CPR VSI. With these results, it is considered that CPR instruction for college students through mass communication or video will be very helpful.

• 농촌의학ㆍ지역보건
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• 제36권1호
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• pp.13-24
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• 2011

본 연구는 고등학교 남학생에서 심폐소생술에 대한 전통적교실학습과 영상자가학습의 교육효과를 통하여 심폐소생술 교육에 효과적인 교육방법 선택에 도움을 주며, 심폐소생술 교육 프로그램 마련에 기초 자료를 제공하고자 하였다. 연구대상자는 G도 소재 G고등학교 2학년 남학생 두 반의 학생으로 1개 반은 실험군, 1개 반은 대조군으로 임의 배정 하였다. 연구 결과는 다음과 같다. 첫째, 심폐소생술 교육 전 후 지식 차이는 대조군(2.38)이 실험군(2.32)에 비해 높게 증가하였지만, 태도 차이는 실험군(2.18)이 대조군(2.06)에 비해 높게 증가하였다. 지식과 태도에서는 통계적으로 유의한 차이는 나타나지 않았다. 둘째, 심폐소생술 교육 전 후 자신감 차이는 실험군(2.40)이 대조군(2.01)에 비해 유의하게 증가하였고(p<0.05), 술기수행 정확도 차이도 실험군(2.67)이 대조군(2.54)에 비해 유의하게 증가 하였다(p<0.05). 본 연구 결과 심폐소생술의 자신감, 술기수행 정확도에서 영상자가학습이 전통적교실학습보다 유의하게 증가하였다. 따라서 영상자가학습 교육 방법을 심폐소생술 교육에 활용할 필요가 있다.

• Journal of Power Electronics
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• 제13권2호
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• pp.256-263
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• 2013

This paper presents an IHQRR (Integrated High Quality Rectifier Regulator) BIFRED (Boost Integrated Flyback Rectifier Energy Storage DC-DC) converter fed BLDC (Brushless DC) motor drive. A reduced sensor topology is derived by utilizing a BIFRED converter to operate in a dual DCM (Discontinuous Conduction Mode) thus utilizing a voltage follower approach for the PFC (Power Factor Correction) and voltage control. A new approach for speed control is proposed using a single voltage sensor. The speed of the BLDC motor drive is controlled by varying the DC link voltage of the front end converter. Moreover, fundamental frequency switching of the VSI's (Voltage Source Inverter) switches is used for the electronic commutation of the BLDC motor which reduces the switching losses in the VSI. The proposed drive is designed for a wide range of speed control with an improved power quality at the AC mains which falls within the recommended limits imposed by international power quality standards such as IEC 61000-3-2.

• 통합자연과학논문집
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• 제5권4호
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• pp.246-252
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• 2012

Multivariate cumulative sum (CUSUM) control charts for simultaneously monitoring both means and variances under multivariate normal process are investigated. Performances of multivariate CUSUM schemes are evaluated for matched fixed sampling interval (FSI) and variable sampling interval (VSI) features in terms of average time to signal (ATS), average number of samples to signal (ANSS). Multivariate Shewhart charts are also considered to compare the properties of multivariate CUSUM charts. Numerical results show that presented CUSUM charts are more efficient than the corresponding Shewhart chart for small or moderate shifts and VSI feature with two sampling intervals is more efficient than FSI feature. When small changes in the production process have occurred, CUSUM chart with small reference values will be recommended in terms of the time to signal.

• Journal of international Conference on Electrical Machines and Systems
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• 제3권2호
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• pp.169-175
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• 2014

This paper presents an improved direct power control (DPC) strategy for grid-connected voltage source inverter (VSI) under unbalanced and harmonic grid voltage conditions. Based on the mathematic model of VSI with the negative sequence, 5th and 7th harmonic voltage components consideration, a PI controller is used in the proposed DPC strategy to achieve the average output power regulation. Furthermore, vector PI controller with the resonant frequency tuned at the two times and six times grid fundamental frequency is adopted to regulate both negative and harmonic components, and then two alternative targets of the balanced/sinusoidal current and smooth active/reactive output power can be achieved. Finally, simulation results based on MATLAB validate the availability of the proposed DPC strategy.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 추계학술대회 논문집
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• pp.111-112
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• 2013

The three-phase four-leg voltage source inverter (VSI) topology can be an interesting option for the three phase-four wire system. With an additional leg, this topology can handle the neutral current, hence the DC link capacitance can be reduced significantly. In this paper the three dimensional space vector modulation (3D SVM) in ${\alpha}{\beta}{\gamma}$ coordinates for the three-phase four-leg VSI is presented. By using the 3D SVM method, the DC link voltage can be reduced by 16% compared with the split DC link capacitor topology and the output distortion can also be reduced under the unbalanced load condition.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.39-42
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• 2009

The aerodynamic characteristics of aircraft winglet with structural deformation was investigated using the static FSI(Fluid-Structure Interaction) system. The system, comprised of CAD, CFD, CSD, VSI, and grid regeneration modules, was constructed. In the process VSI, grid regeneration, and integration modules were developed to combine CSD and CFD modules. As a test model, KC-135A, the double winglet suggested by Whitcomb, was selected and its aerodynamic characteristics for the rigid and deformable models was calculated by applying the static FSI system. As a result, the lift and drag coefficients of test models were reduced to 11% and 1.3%, respectively.