• Journal of Power Electronics
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• v.10 no.1
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• pp.9-13
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• 2010

This paper proposes an input-series-output-parallel connected ZVS full bridge converter with interleaved control for photovoltaic power conditioning systems (PV PCS). The input-series connection enables a fully modular power-system architecture, where low voltage and standard power modules can be connected in any combination at the input and/or at the output, to realize any given specifications. Further, the input-series connection enables the use of low-voltage MOSFETs that are optimized for a very low RDSON, thus, resulting in lower conduction losses. The system costs decrease due to the reduced current, and the volumes of the output filters due to the interleaving technique. A topology for a photovoltaic (PV) dc/dc converter that can dramatically reduce the power rating and increase the efficiency of a PV system by analyzing the PV module characteristics is proposed. The control scheme, consisting of an output voltage loop, a current loop and input voltage balancing loops, is proposed to achieve input voltage sharing and output current sharing. The total PV system is implemented for a 10-kW PV power conditioning system (PCS). This system has a dc/dc converter with a 3.6-kW power rating. It is only one-third of the total PV PCS power. A 3.6-kW prototype PV dc/dc converter is introduced to experimentally verify the proposed topology. In addition, experimental results show that the proposed topology exhibits good performance.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.6
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• pp.404-410
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• 2021

This paper proposes a high step-up converter with zero-voltage transition (ZVT) cell for fuel cell electric vehicle. The proposed converter applies a ZVT cell to a dual floating output boost converter (DFOBC) so that not only the main switch but also the ZVT switch can achieve full-range soft switching. The current rating of the ZVT switch is 17% of the main switch. The proposed converter has high reliability in that no timing issue occurs. Therefore, online calculation is not required. The minimum turn-on time of the ZVT switch that guarantees soft switching at all loads and input/output voltage is obtained by analysis. In addition, the proposed DFOBC allows the use of a 650 V device even at 800 V output and has the advantage of being able to boost the voltage by 3.5 times with 0.56 duty. Planar coupled inductor with PCB winding was successfully implemented with the converter operated at 300 kHz. The 25 kW prototype achieves peak efficiency of 99% and power density of 63 kW/L.

• Journal of Energy Engineering
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• v.23 no.1
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• pp.40-45
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• 2014

The ventilation frequency of 0.5 times in residential facilities is applied mandatorily to the housing facilities containing more than 100 house units to improve the indoor air quality and create comfortable interior conditions and pleasantness for residents. The Building Energy Efficiency Rating system requires the implementation of leakage test based on ventilation frequency with the test results being reflected in the efficiency ratings, thereby stimulating the precise construction of the fittings in the periphery of windows and savings of energy that can be lost due to the infiltration air. The inspection results of the Building Energy Efficiency Rating at the site showed that the ventilation frequency was in the range between 0.63 and 0.71 and that the difference was found to have a significant effect on the amount of energy reduction. It is urgent to conduct the study on highly leakage-proof buildings and construction methods, along with the expansion of mandatory leakage-proof diagnosis of non-residential buildings, considering the mandatory ventilation frequency below 0.6 for passive houses under the European standards and the target set by Korea to introduce the passive house, the rigorous standard for energy efficiency in buildings and mitigating their ecological footprint, by 2017 and achieve the zero house by 2025.

• The Journal of Churna Manual Medicine for Spine and Nerves
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• v.11 no.1
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• pp.65-74
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• 2016

Objectives : This study was designed to assess the general distribution, clinical effectiveness of Korean medical treatment on knee pain and the correlation between Korean medical therapy on knee pain and BMI. Methods : This is an observational study. 65 patients admitted to Daejeon Jaseng Hospital of Korean Medicine with musculoskeletal disorders were observed from July, 2014 to July, 2015. They were analyzed according to sex, age, pain lesion, body mass index(BMI) and treatment efficacy. All patients received a combination of treatments during hospitalization, including acupuncture, pharmacopuncture, herbal medicines and physical therapy. A zero to ten numerating rating scale (NRS) assessing pain, Western Ontario and McMaster Universities Arthritis Index(WOMAC) index and Range of Motion(ROM) was used before and after treatments. Statistical correlations among assessment measurements were evaluated by examining the paired t-test and the Pearson's correlation coefficients. Results : The average BMI of all patients was $24.03{\pm}2.95kg/m^2$. According to clinical definition of obesity by Korean Society for the Study of Obesity, 33.8% of all patients was within normal weight, 1.5% was underweight, 33.8% was overweight, 24.6% was obesity and 6.2% was morbid obesity. For knee pain patients, NRS (Numeric Rating Scale) decreased from $6.28{\pm}1.63$ to $3.94{\pm}2.03$(p<0.001). WOMAC index decreased from $48.14{\pm}17.63$ to $40.37{\pm}18.28$(p<0.001). But, there were no significant correlations in statistics among BMI, knee pain index and knee pain index improvement. Conclusions : Korean medical combination treatment might be effective in reducing pain and improving functional disorders for patients with knee pain. This study further confirmed the efficacy of Korean medical treatment on knee pain. But, more studies on correlation between knee pain and obesity and development of assessment measurement are needed.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.5
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• pp.423-432
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• 1999

This paper proposes a 12­pulse diode rectifier system with low kVA components suitable for powering switch mode power supplies or ac/dc converter applications. The proposed 12-pulse system employs a polyphase transformer, a zero sequence blocking transformer (ZSBT) in the dc link, and an interphase transformer. Results produce near equal leakage inductance in series with each diode rectifier bridge ensuring equal current sharing and performance improvements, The utility input currents and the voltage across the ZSBT are analyzed the kVA rating of each component in the proposed system is computed. The 5th , 7th , 17th and 19th harmonics are eliminated in the input line currents resulting in clean input power. The dc link voltage magnitude generated by the proposed rectifier system is nearly identical to a conventional to a conventional 6-pulse system. The proposed system is suitable to retrofit applications as well as in new PWM drive systems. Simulation and experimental results from a 208V , 10kVA system are shown.

• Journal of Power Electronics
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• v.9 no.5
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• pp.691-699
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• 2009

This paper presents the analysis of series active power filter for reactive power compensation, load balancing, harmonic elimination, and neutral current eradication in three-phase four-wire power systems. Generally, the three-phase four-wire system is widely employed in distributing electric energy to several office building and manufacturing plants. In such systems, the third harmonic and its 3rd harmonics are termed as triple and zero sequence components that do not cancel each other in the system neutral. Consequently, the triple harmonics add together creating a primary source of excessive neutral current. Regarding this concern, this paper presents a new control algorithm for a series hybrid active system, whereas the control approach it adopts directly influence its compensation characteristics. Hence, the advantage of this control algorithm is the direct extraction of compensation voltage reference without phase transformations and multiplying harmonic current value by gain and the required rating of the series active filter is much smaller than that of a conventional shunt active power filter. In order to show the effectiveness of the proposed control algorithm, experiments have been carried out.

• 한국연소학회:학술대회논문집
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• 2003.12a
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• pp.231-236
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• 2003

HCCI(Homogeneous Charge Compression Ignition) combustion is an advanced combustion process explained as a homogeneously premixed charge of a fuel where air is admitted into the cylinder and compression ignited. It has possibility to reduce NOx by spontaneous auto-ignition at multiple points that allows very lean combustion resulting in low combustion temperatures. Particulate matters (PM) could be also reduced by the homogeneous combustion and no fuel-rich zones. Injection timing is extremely advanced to achieve homogeneous charge where a diesel fuel could not be vaporized sufficiently due to low pressure and low temperature condition. Also the over-penetration could be a severe problem. The small injection angle and multi-hole injectors were applied to solve these problems. Dimethyl ether (DME) as an altenative fuel was also applied to relive the bad vaporization problem associated with early injection of diesel fuel. Neat DME has a very high cetane rating and high vapor pressure. Contained oxygen reduces soot during the combustion. Experimental result shows DME can be easily operated in an HCCI engine. PM shows almost zero value and NOx is reduced more than 90% compared to direct-injection diesel engine operating mode but problem of early ignition needs more investigation.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.11
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• pp.563-571
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• 2003

In this paper, the control algorithm and control method for a combined system of shunt passive filter and series active filter in 3-phase 4-wire system are discussed. Moreover, the three-phase four-wire system is widely employed in distributing electric energy to several office building and manufacturing plants. In such systems, the third harmonic and its 3th harmonics are termed as triple and zero sequence components that do not cancel each other in the system neutral. Consequently, the triple harmonics add together creating a primary source of excessive neutral current. Regarding this concern, this paper presents a new control algorithm for a series hybrid active system, whereas the control approach it adopts may directly influence its compensation characteristics. Hence, the advantage of this control algorithm is direct extraction of compensation voltage reference and the required rating of the series active filter is much smaller than that of a conventional shunt active filter. Some experiments were executed and experimental results from a prototype active power filter confirm the suitability of the proposed approach.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1096-1098
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• 2003

In this paper, the control algorithm and control methods for a combined system of shunt passive filter and series active filter in 3-phase 4-wire system are discussed. Moreover, the 3-phase 4-wire system is widely employed in distributing electric energy to several office building and manufacturing plants. In such systems, the third harmonic and odd multiples of $3^{rd}$($9^{th}$, $15^{th}$, etc.) are termed as triple and zero sequence components that do not cancel each other in the system neutral. As a result, the triple harmonics add together creating a primary source of excessive neutral current. Regarding this concern, this paper presents a new control scheme for a series hybrid active system. This series active power filter acts not only as a harmonic compensator but also as a harmonic isolator. Hence the required rating of the series active filter is much smaller than that of a conventional shunt active filter. However, the performance of the combined system is greatly influenced by the filtering algorithm employed in the active power filter. This paper proposes a series active power filter scheme based on performance function. Some experiments was executed and experimental results from a prototype active power filter confirm the suitability of the proposed approach.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.3
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• pp.234-240
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• 2007

In this paper, a novel multi-level inverter for low cost high speed switched reluctance(SR) drive is proposed. The proposed multi-level converter has reduced number of power switches and diodes than that of a conventional asymmetric converter for SRM and smaller voltage rating of the dump capacitor comparing with energy efficient c-dump converter. It can supply five operating modes that is boosted, DC-link, zero, negative bias and negative boosted voltage. The proposed multi-level converter has fast excitation and demagnetization modes of phase current, so dynamic response can be achieved. The proposed multi-level converter is verified by computer simulation and experimental results.