Masaki Imanaka

A new method for securing regulating capacity for load frequency control using seawater desalination plant in small island power system

In this paper, a novel control method using seawater desalination plant instead of battery energy storage system as a controllable load, to suppress the frequency fluctuation is proposed. A high pressure pump is usually installed for reverse osmosis method in the desalination plant. In this research, it is assumed that the power consumption of the high pressure pump can be changed continuously and rapidly through the control of inverter. Since every seawater desalination plant has a storage tank of the produced fresh water, the power consumption of motor can be changed without affecting its daily production. The new method is proposed in this paper for securing regulating capacity while taking into account customers convenience. A linearized power system model was used to calculate the system frequency or regulating capacity. The results of the study indicate that the fluctuation of the system frequency can be suppressed by the control of power consumed by seawater desalination plant.

Fundamental study on stabilization of isolated island power system by use of pump system

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.

A simple control method of waterworks pump power consumption for demand response

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.

Compensation for Photovoltaic Generation Fluctuation by Use of Pump System with Consideration for Water Demand

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.

Feasibility Study on Compensation of Power Fluctuation Caused by Renewable Energy Source Using Desalination System in Island Power System

In this paper, the use of a seawater desalination system as a controllable load is proposed to compensate the power fluctuation of renewable energy sources and control methods are discussed. On/Off control tests were conducted with the actual desalination system without a power converter and variable pump speed tests were conducted with a experimental desalination system with a power converter. The On/Off control turned out to be not so useful for power quality enhancement. With a power converter, the power consumption of the system can be controlled with enough accuracy and response speed for the suppression of the power fluctuations caused by wind turbines and photovoltaic cells.

Feasibility study on power consumption control of desalination plant with mechanical restrictions

It is proposed that the seawater desalination system as a controllable load for compensating the power fluctuation caused by renewable energy in small island power system. For controlling the power consumption of the system, the system modeling is needed. In this paper, the high pressure pump and the RO membrane are modeled, and the accuracy of that model is discussed. In addition, it is necessary to make it clear the boundary condition of the upper and lower limitation of the power consumption of the system. The boundary condition derived from the mechanical restriction of using RO membranes is discussed through modeling and experiment.