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Okinawa, Japan

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. Source

Imanaka M.,University of Tokyo | Baba J.,University of Tokyo | Shimabuku M.,Okinawa Enetech | Tobaru C.,Okinawa Enetech | Uezu Y.,Okinawa Enetech
2015 IEEE Power and Energy Society Innovative Smart Grid Technologies Conference, ISGT 2015 | Year: 2015

Demand response of waterworks has a big possibility because waterworks consume 2 ∼ 3 % of world electricity and water is easy to store. This paper proposes a control method called 'simple dead-beat control' to suppress the two-step power consumption of pumps of waterworks occurred in the step response. Though a dead-beat control method have been proposed, the method needs a lot of parameters to determine. The simple dead-beat control needs only step-response tests to determine the parameters. In tests of this method by use of actual waterworks site, the amplitude of two-step responses is modelled as bivariate quadratic function of the present and next target of pump power consumption. The effectiveness of the suppression is evaluated by the RMS value of the difference between the target and the actual pump power of the test data. © 2015 IEEE. Source

Yoshihara T.,University of Tokyo | Yokoyama A.,University of Tokyo | Imanaka M.,University of Tokyo | Onda Y.,University of Tokyo | And 4 more authors.
IEEJ Transactions on Power and Energy | Year: 2012

Recently, more and more unstable renewable energy based generations such as photovoltaic generations and wind turbine generations have been installed into power systems. This paper focuses a small island power system operation and proposes a novel control method of power consumption of a seawater desalination plant as a controllable load in order to secure more regulating capacity of the power system considering the customer's convenience of the desalination plant. Through a frequency analysis simulation, fuel cost can be reduced and system frequency fluctuation can be suppressed for the proposed control method of seawater desalination plant. © 2012 The Institute of Electrical Engineers of Japan. Source

Sasamoto H.,University of Tokyo | Imanaka M.,University of Tokyo | Baba J.,University of Tokyo | Higa N.,Okinawa Enetech | And 2 more authors.
2013 4th IEEE/PES Innovative Smart Grid Technologies Europe, ISGT Europe 2013 | Year: 2013

The use of a pump system for water supplies as the controllable load is proposed in order to compensate power fluctuations caused by renewable energy sources (RES) in an isolated island, and a control method of pump system power consumption is discussed. The dynamic model of the pump system is proposed taking into account the two step response of the power consumption caused by the pressure surge. Then, as the way to compensate the short cycle power fluctuations of RES by use of the pump system, deadbeat control with consideration of the pressure surge is proposed. Experimental results with deadbeat control show that power consumption can be settled more quickly compared with the case without deadbeat control. This shows that by use of deadbeat control, it is possible to compensate more rapid power fluctuations of RES. © 2013 IEEE. Source

Imanaka M.,University of Tokyo | Sasamoto H.,University of Tokyo | Baba J.,University of Tokyo | Higa N.,Okinawa Enetech | And 2 more authors.
Journal of Electrical Engineering and Technology | Year: 2015

In remote islands, due to expense of existing generation systems, installation of photovoltaic cells (PVs) and wind turbines has a chance of reducing generation costs. However, in island power systems, even short-term power fluctuations change the frequency of grids because of their small inertia constant. In order to compensate power fluctuations, the authors proposed the power consumption control of pumps which send water to tanks. The power control doesn’t affect water users’ convenience as long as tanks hold water. Based on experimental characteristics of a pump system, this paper shows methods to determine reference power consumption of the system with compensation for short-term PV fluctuations while satisfying water demand. One method uses a PI controller and the other method calculates reference power consumption from water flow reference. Simulations with a PV and a pump system are carried out to find optimum parameters and to compare the methods. Results show that both PI control method and water flow calculation method are useful for satisfying the water demand constraint. The water demand constraint has a little impact to suppression of the short-term power fluctuation in this condition. © The Korean Institute of Electrical Engineers. Source

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