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.

-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.

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