Japan International Center for the Study of East Asia Development

Fukuoka, Japan

Japan International Center for the Study of East Asia Development

Fukuoka, Japan
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Simanjorang R.,Japan National Institute of Advanced Industrial Science and Technology | Yamaguchi H.,Japan National Institute of Advanced Industrial Science and Technology | Ohashi H.,Japan National Institute of Advanced Industrial Science and Technology | Nakao K.,Nagasaki University | And 3 more authors.
Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC | Year: 2011

This paper presents the power density developments of high-power isolated dc-dc converter to be utilized in a higher voltage direct-current (HVDC) power-supply system of a data center. This technique results in a prototype of dc-dc converter unit which is smaller by factor of ten when compared with the conventional one, and the area of power-supply system becomes much smaller than before. Consequently, the cooling power for this power-supply system is saved and both the energy and the space saving are available. In order to realize a prototype of the high-power isolated dc-dc converter, the switching power devices composed of a hybrid pair of Si-CoolMOS and SiC-SBD are utilized and operated in a driving pattern of hard switching with a frequency of 200kHz. As a result, an isolated dc-dc converter with the input/output voltage of 400V/400V, a rating power of 5kW, and a high power density of 10W/cm3 has been fabricated. The experimental confirmation was reported and the surge problems due to diode recovery difficulties mentioned before was solved. © 2011 IEEE.

Yamamoto T.,Kyushu Institute of Technology | Rikitake J.,Kyushu Institute of Technology | Matsumoto S.,Kyushu Institute of Technology | Ninomiya T.,Nagasaki University | Abe S.,Japan International Center for the Study of East Asia Development
Proceedings of the International Conference on Power Electronics and Drive Systems | Year: 2013

In recent years, a power supply on chip (SoC) has been attracted attentions of many researchers because it can realize ultimate minimization of the power supply. This realizes higher electric power density and lower manufacturing cost. However, it is necessary to connect parallel at heavy loading conditions because this can handle smaller power per chip. In addition, switching frequency of more than 10 MHz is required for reducing the volume of the power supply. In such a scheme, the traditional analog based PWM will face the problems and a new control strategy is required. This paper proposes a new control strategy of the power-SoC based on parallel connections of dc-dc converters by digital control. We also report the simulation and experimental results of the proposed strategy. The results show that the proposed strategy works well and improves the efficiency over the wide range. © 2013 IEEE.

Watanabe A.,Kyushu Institute of Technology | Tsukuda M.,Kyushu Institute of Technology | Tsukuda M.,Japan International Center for the Study of East Asia Development | Omura I.,Kyushu Institute of Technology
Microelectronics Reliability | Year: 2013

A "real time" monitoring system which enables to observe internal degradation process to failure of power semiconductors under power cycling test is proposed. The system was realized by combining a scanning acoustic tomography (SAT/SAM), power stress controlling, device cooling, water jet system and chip temperature monitoring. Two contradictory problems, namely, electrically wiring for power cycling and waterproof of device for SAT imaging were compatible with each other by experimental setup with an original water tank. Self-heating of power devices was suppressed by controlling temperature of water which is couplant of ultrasonic wave for the SAT. A demonstration of this system was performed by using an IGBT module which maximum rating of collector current was 400 A (DC). © 2013 Elsevier Ltd. All rights reserved.

Sakamoto H.,Japan International Center for the Study of East Asia Development
Studies in Regional Science | Year: 2012

This paper discusses population distributions in a region that needs to solve regional income disparity problems. The targeted region was the Jiangsu Province in China where the intra regional income disparity city level and prefecture level (shows expansion with recent economic growth. First, the population population distribution) necessary for regional income disparity to completely disappear under very simple assumptions was estimated. The 'desirable' population was named the "convergence population". Differences in the real estimated population and the convergence population were compared, and the degree of the solution for income disparity was verified. Consequentially, population cannot be absorbed sufficiently in rich regions, and income disparity is far from being solved. On the other hand, it is possible to think of a population movement plan for the future by estimating the convergence population. The population and accompanying income disparity were estimated in several projections by combining the registered population with the convergence population. In this estimation, a larger adjustment rate produced a greater decrease in income disparity. © JSRSAI 2012.

Yang S.,Kyushu University | Abe S.,Japan International Center for the Study of East Asia Development | Shoyama M.,Kyushu University
2010 International Power Electronics Conference - ECCE Asia -, IPEC 2010 | Year: 2010

Low-profile, high efficiency power supply is today's industry trend for Plasma Display Panel (PDP) application system. Transformer is the major challenge and bottleneck for achieving low-profile, high power density converter. Generally, it is necessary for low-profile converter to operate it at high switching frequency. However, it is very difficult to design converter using flat magnetic component because flat transformer temperature becomes high at high switching frequency. In this paper, the design and analysis of flat transformer in LLC resonant converter for the PDP TV is proposed to reduce temperature of the transformer. In this proposed converter, flat transformer is integrated into advanced power conversion application systems. Low-profile power module of profile of about 14mm is achieved. Temperature inside of transformer repressed to 71°C and an overall efficiency of about 96.6% was obtained. © 2010 IEEE.

Sakamoto H.,Japan International Center for the Study of East Asia Development
Studies in Regional Science | Year: 2011

This study uses the railway transportation data of China to analyze trends in provincial logistics. In particular, the railway O-D (Origin and Destination) table (formally titled "Freight Exchange of National Railway between Administration Regions") in the "Year Book of China Transportation and Communications" is the only material that supplements provincial logistics in China. First, the study calculates the shares among provinces. Second, the study estimates the future distribution by stochastic models represented by the Markov chain. Third, the study suggests a simple indicator that analyzes the changes in shares. According to this indicator, 0% shows no change in shares, whereas 100% show that share changes from one side to another. These results clearly indicate the trends and patterns in provincial logistics change slowly, resulting in less than 10% share change and stabilization of future convergence distributions. Therefore, few changes can be expected in the provincial logistics trends in China However, this study is limited by the data obtained, because it does not analyze other modes of transportation. If the trends in logistics do not change through time, it is difficult to suggest a logistic policy, especially in terms of railway transportation, to reduce regional disparity. The policy for constructing a railway logistic center in poor regions to reduce disparity is not realistic. On the other hand, the demand for railway construction based on actual demand will continue for a while. As a result, there is a possibility the logistic policy will be influenced against our expectations if the trends in logistics greatly change. Therefore, a logistic policy for economical reasons is indispensable.

Sakamoto H.,Japan International Center for the Study of East Asia Development
Studies in Regional Science | Year: 2013

This study investigated by a comparison analysis of the intra-provincial disparity between Guangxi and Yunnan using statistical data.These two provinces(autonomous region) belong to the southwest region of China, and are comparatively poor.First, this study showed the two provinces do not reach the national average in many economic indicators.Next, the intra-provincial disparity of the two provinces was verified by the prefectural data.Information on the city was deleted beforehand, and the analysis assumed to be an analysis of data from the rural area.Then, the comparison of the structure of the intra-provincial disparity in the rural area between the two provinces was statistically analyzed. A part of the factors for disparity are generally seen in the advancement of industrial structure and urbanization.Especially, data analysis at the prefectural level shows disparity, even when disparity is not found in the rural area itself.Disparity arises from the difference in the situations in the stages for developing from a rural area.Moreover, when a comparison of the kernel density function was done by using a statistical index, it was clear that the economic structure in the rural area is different between Guangxi and Yunnan. Since economic structure shows a difference, a common economic policy to both prefectures is not suitable for Guangxi and Yunnan.Obviously, each province has a separate government, so the possibility of developing a common policy is low, but it is certain that a policy suitable for the actual conditions of each province is desired.This is a future subject for more detailed analysis.

Hariya A.,Nagasaki University | Ishizuka Y.,Nagasaki University | Matsuura K.,TDK Corp | Yanagi H.,TDK Corp | And 2 more authors.
Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC | Year: 2014

In this paper, a proposed pulse width modulation (PWM) control method for the isolated current-mode resonant DC-DC converter with MHz level switching frequency is presented. The circuit topology is same as a conventional resonant converter with synchronous rectification and without any additional components. The control technique for the output voltage regulation is proposed with the unique PWM control for synchronously-rectifying switches. By using the transformer's leakage inductance and the PWM control, the boost conversion can be realized. In addition, to achieve the zero-voltage switching (ZVS) operation, phase-shift between primary and secondary-side switches is adapted. The ZVS operation can maintain for primary-side switches. In this paper, proposed technique for achieving stable ZVS operation has been discussed. Some experiments have been done with 5MHz isolated DC-DC converter which has Gallium Nitride field effect transistor (GaN-FET), and the total volume of the circuit is 16.14cm3. The data show that the maximum power efficiency is 89.4%. © 2014 IEEE.

Yang S.,Kyushu University | Abe S.,Japan International Center for the Study of East Asia Development | Shoyama M.,Kyushu University
Proceedings of EPE-PEMC 2010 - 14th International Power Electronics and Motion Control Conference | Year: 2010

This paper presents the design of two flat transformers in LLC resonant converter. The trend toward high power density, high efficiency, and low profile in power supplies has exposed a number of limitations in the use of magnetic component structures. In the LLC resonant converter, the switching loss is reduced by soft-switching. Therefore, LLC resonant converter can be operated at high switching frequency with high efficiency. However, transformer loss becomes problems at high switching frequency. As a result, flat transformers temperature becomes high in proportion to the transformer loss. Therefore, it is necessary to reduce the transformer temperature by analyzing the loss. In this paper, design for reduction transformer temperature is presented. © 2010 IEEE.

Imai K.,Japan International Center for the Study of East Asia Development | Palit D.,Tata Energy Research Institute
International Journal of Environmental Sustainability | Year: 2014

For India, it is crucial to promote rural electrification to raise the well-being of the people since electrification provides a wide range of opportunities for people to change the social, economic, and environmental aspects of their lives for the better. In its rural areas, which have a larger number of households and higher populations than its urban areas, two types of electrification are in progress. One is electrification by connecting to the conventional grid. The other is electrification with renewable energies such as solar, biomass, hydro, and so on. Many studies show positive socio-economic impacts of electrification with renewable energies in rural areas of developing countries including India. However, are there any significant socio-economic impacts of the electrification with renewable energies? This study is particularly interested in its impacts on local economies such as the creation of new businesses and jobs, agricultural and other productive activities, and household income. The study investigated quantitatively and qualitatively the impacts of two types of electrification on local economies for comparison by conducting the interview survey in two grid connected villages and also two solar mini-grid villages in Sundarbans, State of West Bengal, India, and then compared those results from two types of villages in terms of electrification technologies used to identify significant characteristics in the impacts on local economies in solar mini-grid villages compared to grid connected villages. The study found that: first the share of the households whose primary occupation is small business is significantly larger in solar mini-grid villages than in grid connected villages; second the use of electricity is not allowed for agriculture in solar mini-grid villages because of the limited capacity of solar power plants; and third the increase of household income after electrification is significant both in solar minigrid villages and in grid connected villages. However, further study is necessary to ascertain whether these impacts on local economies in sample solar mini-grid villages can be generally found in rural electrification with renewable energies. The study also found that while the share of households without access to electricity even after their village was electrified is much larger in solar mini-grid villages than grid connected villages, most of these unelectrified households in the solar mini-grid villages have been covered through solar home systems. The study concludes that solar energy is also able to provide the required energy for development of the local economy in the form of markets, powering the schools, health centers, etc. Thus, it could be an alternative means of electrification that compliments grid electrification to enhance the rural electrification in the developing countries rich with solar resources. © Common Ground, Kenichi Imai, Debajit Palit, All Rights Reserved.

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