Okinawa, Japan

The Okinawa Electric Power Company, Incorporated , OEPC or Okiden for short, is an electric utility with its exclusive operational area of Okinawa Prefecture, Japan. It is the smallest by electricity sales among Japan’s ten regional power utilities, indeed, its electricity sales is approximately 1⁄40 of that of The Tokyo Electric Power Company, though it is the largest by revenue among companies headquarterd in Okinawa. Wikipedia.


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Amano H.,Japan Central Research Institute of Electric Power Industry | Shima W.,Japan Central Research Institute of Electric Power Industry | Kawakami T.,Japan Central Research Institute of Electric Power Industry | Inoue T.,Japan Central Research Institute of Electric Power Industry | And 4 more authors.
2013 4th IEEE/PES Innovative Smart Grid Technologies Europe, ISGT Europe 2013 | Year: 2013

As one of the measures to realize large-scale renewable energy penetration, utilization of BESS (battery energy storage system) in LFC (load frequency control) is expected. In this paper, the control performance of a LFC system to make effective use of existing LFC thermal unit and BESS is verified by utilizing Miyako Island field test facility. The field test results show that the proposed LFC system can more suppress frequency deviation than LFC using only existing LFC unit and can significantly reduce the required capacity of BESS compared with LFC using only BESS. © 2013 IEEE.


Hatta H.,Japan Central Research Institute of Electric Power Industry | Shima W.,Japan Central Research Institute of Electric Power Industry | Kawakami T.,Japan Central Research Institute of Electric Power Industry | Kobayashi H.,Japan Central Research Institute of Electric Power Industry | And 4 more authors.
2013 4th IEEE/PES Innovative Smart Grid Technologies Europe, ISGT Europe 2013 | Year: 2013

The installed capacity of photovoltaic (PV) systems has been increasing in Japan. When the capacity of PV systems is increased, electricity production may exceed the demand and surplus electricity from the PV systems may become a problem in the power system. To manage the surplus electricity, the PV output may have to be reduced during the light load period. In this paper, PV output reduction methods using a battery energy storage system (BESS), which is located on both the power system side and customer side, and customer equipment are proposed. The proposed methods including both centralized control method and local control method are demonstrated by field tests at the Miyako Island field test facility. © 2013 IEEE.


Tamaki M.,Okinawa Electric Power Co. | Takagi K.,Toshiba Corporation | Shimada K.,Toshiba Corporation | Kawakami N.,MItsubishi Electric | Iijima Y.,MItsubishi Electric
15th International Power Electronics and Motion Control Conference and Exposition, EPE-PEMC 2012 ECCE Europe | Year: 2012

Population growth, global warming, depletion of fossil fuels, and ensuring nuclear power safety are serious energy issues, and solutions to these issues have been becoming increasingly important globally. One solution that has been focused on is the use of renewable energy. The introduction of photovoltaic (PV) and wind turbine (WT) systems has been accelerating around the word. However, the power generation efficiency of these renewable energy systems is low, and the power generation level is unstable. At present, therefore, the ratio occupied by renewable energy in the overall power generation system cannot be considerably increased from the viewpoint of grid stability. Nevertheless, renewable energy is one of the most important energy sources for the future, and various studies and field demonstrations are underway. This paper gives an overview of a MW PV plant equipped with a large-capacity battery system (NAS battery), together with the results of grid stability enhancement achieved with the battery system, in trials conducted by Okinawa Electric Power Company Co., at a research facility on Miyako Island. In particular, this paper reports on power stability control and frequency compensation using a power conditioning system (PCS) for energy storage. This MW PV plant and power storage system were installed in an independent power grid on Miyako Island. The total grid capacity is about 50,000 kW. The MW PV system and an existing WT system make up about 16% of the total system capacity, and the battery system makes up about 8%. Power supply instability and frequency fluctuations become larger with an increasing proportion of power generated by renewable energy. The developed PCS using the battery system showed good performance in solving this problem. © 2012 IEEE.


Yamashita K.,Japan Central Research Institute of Electric Power Industry | Sakamoto O.,Japan Central Research Institute of Electric Power Industry | Kitauchi Y.,Japan Central Research Institute of Electric Power Industry | Nanahara T.,Japan Central Research Institute of Electric Power Industry | And 3 more authors.
Electrical Engineering in Japan (English translation of Denki Gakkai Ronbunshi) | Year: 2012

Integration of wind power generation into small islands has been one of the demonstration projects in Okinawa Prefecture. Since such integration could degrade power quality including frequency in an island grid, a frequency stabilizing system using flywheels has been installed into a small island. In order to establish a proper frequency stabilizing scheme for the small island, an accurate model of a diesel generator including governor is vital. Therefore, the model was developed based on the measured values of generator dump tests. A new frequency stabilizing scheme was also developed through time-domain simulation of the island grid model, which consists of the above-mentioned diesel generator model and an equivalent load change representing wind power variation. The proper parameters of the scheme were derived considering role sharing between the diesel generators and the flywheels. The developed stabilizing scheme was applied to the flywheels in the island grid and revealed excellent performance in mitigating frequency variation. © 2012 Wiley Periodicals, Inc.


Noda T.,Japan Central Research Institute of Electric Power Industry | Nakamatsu T.,Okinawa Electric Power Co. | Mekaru T.,Okinawa Electric Power Co.
IEEJ Transactions on Electrical and Electronic Engineering | Year: 2015

Because of the presence of large capacitance, measuring the series resistance of a cable as a voltage drop is not an easy task especially at high frequencies. Considering this fact, this letter proposes a method to extract series resistance values of a single-core cable at high frequencies from the measured frequency response of its open-ended input impedance. The proposed method has been applied to the measurement of the series resistance of an existing 66-kV underground cable, and the result is presented. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.


Yamashita K.,Japan Central Research Institute of Electric Power Industry | Sakamoto O.,Japan Central Research Institute of Electric Power Industry | Kitauchi Y.,Japan Central Research Institute of Electric Power Industry | Nanahara T.,Japan Central Research Institute of Electric Power Industry | And 3 more authors.
IFAC Proceedings Volumes (IFAC-PapersOnline) | Year: 2011

Integrating wind power generation into small islands has been one of the demonstration projects in Okinawa Prefecture, Japan. Since such integration could deteriorate power quality, including frequency, in an island grid, a frequency-stabilizing system using flywheels has been integrated into a small island. In order to establish a proper frequency-stabilizing scheme for a small island, an accurate model of a diesel generator including a governor is vital. Therefore, a model was developed through generator dump tests. A new frequency-stabilizing scheme was also developed through the time-domain simulation of the island grid model, which consists of the above mentioned diesel generator model and negative load change representing wind power variation. The developed stabilizing scheme was applied to the flywheels in the island grid and revealed great performance for mitigating frequency variation. © 2011 IFAC.


Imanaka M.,University of Tokyo | Baba J.,University of Tokyo | Kuniba Y.,Okinawa Electric Power Co. | Higa N.,Okinawa Enetech
IEEJ Transactions on Power and Energy | Year: 2015

Installation of renewable energy sources in island grids is focused on as large expense of island power generation and their power fluctuations should be conpensated. Desalination system is being focused on as a controllable load. This paper proposes a model for the desalination system, estimates controllable ranges under restrictions and evaluates the ability to suppress the power fluctuations. The model calculates the pressure, flow and power consumption. Parameters of the model are fitted by tests with an experimental system. Next, controllable ranges of power consumption under restrictions of the membrane etc. are estimated both by tests and by the model. Controllable ranges with fixed valve openness are estimated as 27 to 43 percent of its rated power. Finally, to evaluate transient response, step and ramp response tests and photovoltaic (PV) output suppression tests are conducted. Most of the fluctuations of PV output are suppressed when PV output is within the controllable range. © 2015 The Institute of Electrical Engineers of Japan.


Tamaki M.,Okinawa Electric Power Co. | Uehara S.,Okinawa Electric Power Co. | Takagi K.,Toshiba Corporation | Ichikawa T.,Toshiba Corporation
Proceedings of the IEEE Power Engineering Society Transmission and Distribution Conference | Year: 2012

The Miyako lsland Mega Solar Demonstration Research Facility has two objectives. The first objective is to examine the impact on the power system from installing large scale renewable energy such as photovoltaic power. The second objective is to study measures for power system stabilization by analyze data from PV and rechargeable battery. This pilot project will be conducted for three years (until March 2013) by the Okinawa Electric Power Company, Inc. This paper will explain the overview of the Miyako Island Mega Solar Demonstration Research Facility, then explain in detail about each device such as photovoltaic system and storage battery and end with the report of favorable demonstration results recorded from the execution of the research. © 2012 IEEE.


Patent
Okinawa Electric Power Co. | Date: 2012-02-22

Process for producing a material similar to leather, which foresees:- a step of providing a base material (1) in band form and comprising a cellulose fibre impregnated with a copolymer dispersion;- a step of impregnating the base material (1) in band form with at least one liquid product;- a step of compressing the base material (1) in band form in a duct (2), wherein the base material (1) in band form is compressed transversally in the direction of its own width sliding in a compression portion of the duct (2) having a smaller width than the width of the base material (1);- a step of spreading out the base material (1) in band form, wherein the latter opens out at least partially along its own width outside of the compression portion of the duct (2); Moreover, the process in object foresees that the compression step and the spreading out step are repeated cyclically.


Patent
Okinawa Electric Power Co. | Date: 2011-08-18

Process for producing a material similar to leather, which foresees:

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