• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.786-794
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• 2015

In this paper, a new power control strategy for the bipolar-type low voltage direct current (LVDC) distribution system is being proposed. The dc distribution system is considered as an innovative system according to the increase of dc loads and dc output type distribution energy resources (DERs) such as photovoltaic (PV) systems and energy storage systems (ESS). Since the dc distribution system has many advantages such as feasible connection of DERs, reduction of conversion losses between dc output sources and loads, no reactive power issues, it is very suitable solution for new type buildings and residences interfaced with DERs and ESSs. In the bipolar-type, if it has each grid-interfaced converter, both sides (upper, lower-side) can be operated individually or collectively. A complementary power control strategy using two ESSs in both sides for effective and reliable operation is proposed in this paper. Detailed power control methods of the host controller and local controllers are described. To verify the performances of the proposed control strategy, simulation analysis using PSCAD/EMTDC is being performed where the results show that the proposed strategy provides efficient operations and can be applied to the bipolar-type dc distribution system.

• New & Renewable Energy
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• v.4 no.1
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• pp.5-10
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• 2008

Hydrogen fuel cell is clean and efficient technology along with high energy densities. While there are many different types of fuel cells, the proton exchange membrane fuel cell stands out as one of the most promising for transportation and small stationary applications. This paper focuses on design of bipolar plate for proton exchange membrane fuel cell. The bipolar plate model is realistically and accurately simulated velocity distribution, current density distribution and its effect on the PEMFC system using CFD tool FLUENT.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.82.2-82.2
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• 2010

The development of bipolar plate having high efficiency and chemical properties has a major impact on fuel cell applications commercialization. Even though graphite bipolar plate has high electric conductivity and chemical resistance, it has demerits about mass production and brittle property for commercialization. Hence, metallic bipolar plate can be substitute for fuel cell bipolar plate. Although its inadequate corrosion behavior under PEMFC environment lead to a deterioration of membrane by dissolved metal ions, metallic bipolar plate for PEMFC is more suitable for automotive and residential power generation system because of its high mechanical strength, low gas permeability and applicability to mass production. Therefore, several types of coating has been applied to prevent corrosion and oxide film growth and to achieve more high durability. This work presents durability of coated metal bipolar plate for low temperature PEMFC which made for fuel cell vehicle. This results showed surface treatment increase long-term durability, even electric conductivity and corrosion resistance.

• ETRI Journal
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• v.26 no.1
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• pp.13-20
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• 2004

We propose a new optical code division multiple access (OCDMA) scheme for reducing multiple access interference (MAI) and enhancing performance for optical subscriber access networks using modified pseudorandom noise (PN)-coded fiber Bragg gratings with bipolar OCDMA decoders. Through the bipolar OCDMA decoder and the modified PN codes, MAI among users is effectively depressed. As the data are encoded either by a unipolar signature sequence of the modified PN code or its complement according to whether the data bit is 1 or 0, the bit error ratio (BER) can be more improved with the same signal to interference plus noise ratio over the conventional on-off shift keying-based OCDMA system. We prove by numerical analysis that the BER of the proposed bipolar OCDMA system is better than the conventional unipolar OCDMA system. We also analyze the spectral power distortion effects of the broadband light source.

• Korean Journal of Biological Psychiatry
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• v.1 no.1
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• pp.79-87
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• 1994

For the purpose of evaluating the human leukocyte antigen(HLA) disease-association with bipolar disorder, HLA class I and class II allelic frequencies were assessed in 37 bipolar patients and were compared to the data from normal population. HLA class 1 typing was performed with microlymphocytotoxicity method while class II(DRB1) genotyping with reverse dot blot hybridization and sandwich method. Statistical analysis consisted of relative risk, Haldane's modified relative risk, Fisher's exact test and Bonferoni's corrected P. The results were as follows : 1) Bipolar patients showed increased allelic frequency of HLA A3 which has statistical significance. 2) Allelic frequencies of HLA B7, B14 and B54 were higher, while those of B51 and B55 were lower in bipolar patients, but they were not statistically significant. 3) Both of increased frequencies of DR2 in bipolar patients and DR15 in normal controls had statistical significance. The results of the present study suggested that some of HLA allelic types might be associated with bipolar disorder. To clarify the genetic influence of HLA to bipolar disorder, we should do consecutive study of bipolar disorder with new information about HLA system including alleles.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.3
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• pp.409-414
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• 2011

To promote the industry of PEMFC, the commercialization of its parts especially bipolar plate is needed. The bipolar plate is one of key parts for PEMFC, which occupies cost portion of 5~8% in the system. To replace the bipolar plate of machined graphite highly costly, the stamped thin matal or the molded carbon composite has been developed. According to the merits and demerits of each material and its forming process, the stamped metallic plate has been considered to the bipolar plate of PEMFC for automotive, and on the other hand, the molded composite plate has been considered to one for building applications. Hankook Tire Co., Ltd. has developed the carbon composite material and the manufacturing process for the bipolar plates. The developed bipolar plates were proved to be fully applicable to PEMFC of building applications in characteristics and performance, and so government strategic project to develop the mass-production technology for bipolar plates was started and is being conducted by the company. Through the government project for obtaining both the commercialization technology and production capacity for the bipolar plates, the price and the performance of domestic PEMFCs are expected to become competitive in international market.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.144.2-144.2
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• 2010

Bipolar plate는 고분자 전해질 연료전지(PEMFC)에서 핵심 부품 중의 하나이고, 전해질 막이나 촉매 등에 비해서는 상대적으로 쉽게 접근할 수 있기 때문에 많은 연구가 수행되고 있다. Bipolar plate를 제조하는 기술은 크게 금속을 프레스 가공하는 방법, graphite 판을 직접 밀링하는 방법 및 고분자/카본계의 press molding 법 등 3가지로 분류되며, 본 연구에서는 3번째 방법에 의해서 bipolar plate를 대량 생산하는 방법에 대해 연구하였다. 고분자 매트릭스는 에폭시계 수지를 사용하였고, 카본계 재료는 graphite 분말과 carbon nanotube를 사용하였다. 이들 재료들을 일정한 비율로 혼합한 후 differential scanning calorimetry(DSC)를 사용하여 열분석 하였고, 그 결과를 Kissinger equation에 대입하여 경화반응 속도론을 연구하였다. 또한, 경화된 에폭시/탄소 복합재료의 전기전도도, 유리전이온도, 표면에너지 특성 등을 분석하였다.

• Transactions of the Korean hydrogen and new energy society
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• v.28 no.5
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• pp.481-491
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• 2017

In this study, we developed 300 W lightweight DMFC system for charging secondary battery in small unit military operation. In order to reduce the volumetric shape and weight of the system considering the environment of the individual soldier's, the arranging of system components has been optimized. A metal bipolar plates made of STS-470FC have been implemented to the DMFC stack to meet the weight demand of the system. As a result of the performance test of the stack, the target value was satisfied by outputting 561 W exceeding 24% of the stack output 450 W required to output 300 W required for the entire system. Moreover, 2,655 hours exceeding 1,000 hours also has been satisfied. To ensure good robustness of the metallic bipolar plate based DMFC stack, finite element method based simulations are conducted using a commercial ANSYS Fluent software.

• Journal of Power Electronics
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• v.18 no.4
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• pp.1223-1234
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• 2018

In this paper, a new three-port multidirectional DC-DC converter is proposed for integrating an energy storage system (ESS) to a bipolar DC microgrid (BPDCMG). The proposed converter provides a voltage-balancing function for the BPDCMG and adjusts the charge of the ESS. Thanks to the multi-functional operation of the proposed converter, the conversion stages of the system are reduced. In addition, the efficiency and weight of the system are improved. Therefore, this converter has a significant capability when it comes to use in portable BPDCMGs such as electric DC ships. The converter modes are analyzed and small-signal models of the converter in each of the independent modes are extracted. Finally, comprehensive simulation studies are carried out and a BPDCMG laboratory prototype is implemented in order to verify the performance of the proposed voltage balancer using the burst mode control scheme.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.39-42
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• 2007

Hydrogen fuel cell is clean and efficient technology along with high energy densities. While there are many different types of fuel cells, the proton exchange membrane fuel cell stands out as one of the most promising for transportation and small stationary applications. This paper focuses on design of bipolar plate for proton exchange membrane fuel cell. The bipolar plate model is realistically and accurately simulated velocity distribution, current density distribution and its effect on the PEMFC system using CFD tool FLUENT.