• Journal of Power Electronics
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• 제15권6호
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• pp.1609-1618
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• 2015

DC microgrids are considered as prospective systems because of their easy connection of distributed energy resources (DERs) and electric vehicles (EVs), reduction of conversion loss between dc output sources and loads, lack of reactive power issues, etc. These features make them very suitable for future industrial and commercial buildings' power systems. In addition, the bipolar-type dc system structure is more popular, because it provides two voltage levels for different power converters and loads. To keep voltage balanced in such a dc system, a bidirectional dual buck-boost voltage balancer with direct coupling is introduced based on P-cell and N-cell concepts. This results in greatly enhanced system reliability thanks to no shoot-through problems and lower switching losses with the help of power MOSFETs. In order to increase system efficiency and reliability, a novel burst-mode control strategy is proposed for the dual buck-boost voltage balancer. The basic operating principle, the current relations, and a small-signal model of the voltage balancer are analyzed under the burst-mode control scheme in detail. Finally, simulation experiments are performed and a laboratory unit with a 5kW unbalanced ability is constructed to verify the viability of the bidirectional dual buck-boost voltage balancer under the proposed burst-mode control scheme in low-voltage bipolar-type dc microgrids.

• 전력전자학회논문지
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• 제14권1호
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• pp.72-81
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• 2009

본 논문에서는 대기압 플라즈마 발생용 정현파펄스형 교류 전원 장치에 대한 연구를 진행하였다. 정현파펄스형 전원장치는 기존의 LC공진을 이용한 교류 전원장치보다 높은 dv/dt를 갖게 되므로 안정적인 플라즈마 공급이 가능하며 펄스형에 비해 고조파 노이즈가 적고, 정전류 턴온-영전압 턴오프 형태로 동작하므로 매우 높은 효율을 갖는다. 또한 플라즈마 점화 기능을 강화하고 안정적인 전압제어를 위해 3상 부스트형 컨버터를 입력단에 사용하여 입력 역률이 매우 높은 시스템을 구성할 수 있다. 실험실 수준의 10kW부하시설을 사용하여 본 연구의 결과를 입증하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2013년도 추계학술대회 논문집
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• pp.105-106
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• 2013

This paper proposes a new topology with active switched-capacitor and switched-inductor impedance network, which can obtain a high boost factor with small shoot-through time. The proposed topology uses an active switched capacitor and switched-inductor impedance network in order to couple the main circuit and input dc source for boosting the output voltage. The proposed topology contains all advantages of the classical Z-source inverter. Comparing with other topologies, the proposed topology uses lesser component and the voltage boost inversion ability significantly increases. The theoretical analysis, pulse width modulation control strategies, and a comparison with classical ZSI have been given in this paper. Both simulation and experimental results will be presented to verify the advantages of the proposed topology.

• Journal of Power Electronics
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• 제9권3호
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• pp.335-342
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• 2009

The Z-source inverter (ZSI) provides unique features such as the ability to boost dc voltage with a single stage simple structure. Although the dc capacitor voltage can be boosted by a shoot-through state, the voltage stress across the switching devices is rapidly increased, so high switching device power is required at the ZSI. In this paper, algorithms for minimizing the voltage stress are suggested. The possible operating region for obtaining a desired ac output voltage according to both the shoot-through time and active state time is investigated. The reference capacitor voltages are derived for minimizing the voltage stress at any desired ac output voltage by considering the dc input voltage. The proposed methods are carried out through the simulation studies and experiments with 32-bit DSP.

• Journal of Power Electronics
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• 제13권4호
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• pp.507-515
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• 2013

This paper presents an isolated bidirectional dc/dc converter based on primary parallel isolated boost converter (PPIBC). This topology is an efficient solution in low voltage high power applications due to its ability to handle high currents in the low voltage side. In this paper, the converter has been modeled using non-ideal components and operated without any additional circuitry for startup using a digital soft-start procedure. Simulated and measured loop gains have been compared for the validity of the model. On-the-fly current direction change has been achieved with a prototype interconnecting two battery banks. A second prototype has been constructed and tested for supercapacitor operation in constant power charge mode.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.105-107
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• 2018

This paper presents a new hybrid multilevel converter topology, which consists of a combination of the series connected switched capacitor units with boost ability, and an H-bridge with T-type bidirectional switches. The proposed converter boosts the input voltage without any bulky inductors, and has the small number of components, which can make the size and cost of a power converter greatly reduced. The output filter size and harmonics are also reduced by the high quality multilevel output. In addition, there is no need for complicated methods to balance the capacitor voltage. Simulation and experimental results with a nine-level converter system are presented to validate the proposed topology and modulation method.

• IMMUNE NETWORK
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• 제5권1호
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• pp.1-10
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• 2005

Background: Chronic infection with hepatitis B virus (HBV) affects about 350 million people worldwide, which have a high risk of development of cirrhosis and hepatocellular carcinoma. Treatment of chronic HBV infection relies on IFN-${\alpha}$ or lamivudine. However, interferon-${\alpha}$ is effective in only about 30% of patients. Also, the occurrence of escape mutations limits the usage of lamivudine. Therefore, the development and evaluation of new compounds or approaches are urgent. Methods: We comparatively evaluated DNA and adenoviral vaccines expressing HBV antigens, either alone or in combined regimens, for their ability to elicit Th1-type immune responses in Balb / c mice which are believed to be suited to resolve HBV infection. The vaccines were tested with or without a genetically engineered IL-12 (mIL-12 N220L) which was shown to enhance sustained Th1-type immune responses in HCV E2 DNA vaccine. Results: Considering the Th1-type cytokine secretion and the IgG2a titers, the strongest Th1-type immune response was elicited by the DNA prime-adenovirus boost regimen in the presence of mIL-12 N220L. In addition, the codelivery of mIL-12 N220L modulated differentially the immune responses by different vaccination regimens. Conclusion: Our results suggest that the DNA prime-adenovirus boost regimen in the presence of mIL-12 N220L may be the best candidate for HBV vaccine therapy of the regimens tested in this study and will be worthwhile being evaluated in chronic HBV patients.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.10-13
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• 2000

This paper proposes the virtual implementation of solar cell(VISC) for photovoltaic system. It is required to make operation condition of solar cell arrays where is the limit of time and space, The main advantage of the simulator is its ability to simulate different types and sizes of arrays considering V-I characteristics of data sheet. The VISC with buch-boost converter can be used to study the short-term and long-term performances of PV cells. The simulator is a far more cost effective and reliable replacement for field and filight testing.

• 한국정보시스템학회지:정보시스템연구
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• 제14권2호
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• pp.293-317
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• 2005

Female customers form a major customer group for Internet shopping and their trust on Internet stores seems to be significantly related with their transactions. This paper focuses on female customers' trust on Internet stores, hypothesizing that online service quality has a positive impact on trust and that trust, in turn, together with service quality has a positive effect on loyalty. We investigate trust from three dimensions(benevolence, integrity, and ability) and at the same time, unlike existing research, treat service quality to have five dimensions (intangibles, reliability, responsiveness, assurance, and empathy) as known in SERVQUAL(Parasuraman et al., 1988). Survey data is obtained from the female college student sample. Our research model is justified in terms of construct validity, internal consistency, and goodness of fit. Research hypotheses are tested using SEM(Structural Equation Modeling). The results are as follows: First, assurance and empathy dimensions of service quality have significant impacts on benevolence/integrity dimension of trust. Second, out of the five service quality dimensions, only assurance has a positive effect on ability dimension of trust. Third, assurance dimension of service quality and ability dimension of trust are positively related with customer loyalty. The most important factors for female customers' loyalty are found to be assurance(service quality) and ability(trust). The significance of assurance is in line with findings from existing research. But its relationship with the trust dimensions is uncovered in this research, and the only dimension that impacts on ability is assurance. We find that female customers build trust about internet stores based on their ability rather than on their benevolence/integrity and that the female customers' perception on the internet stores' ability can be improved by higher service quality from the aspect of assurance. Importantly enough, these findings offer practical guidelines to Internet stores to boost female customers' loyalty.

• Journal of Power Electronics
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• 제12권1호
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• pp.201-207
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• 2012

This paper presents the results and gained experiences from the Project Based Learning (PBL) of magnetic component design within a Power Electronics Course. PBL was applied during the laboratory exercises through a design-project task based on a boost converter test board. The students were asked to calculate the main boost converter's circuit parameters' capacitor C and inductor L, and then additionally required to design and build-up the inductor L, in order to meet the project's goals. The whole PBL process relied on ideas from the CDIO (Conceive, Design, Implement, Operate), where the students are encouraged to consider the whole system's process, in order to obtain hands-on experience. PBL is known to be a motivating and problem-centered teaching method that gives students the ability to transfer their acquired scientific knowledge into industrial practice. It has the potential to help students cope with demanding complexities in the field, and those problems they will face in their future careers.