Takafumi Morisaki

Controller design for liquid level control of separator in an OTEC plant with Uehara cycle considering disturbances

This research deals with the design of PI controller for the liquid level control of separator in an ocean thermal energy conversion (OTEC) plant with Uehara cycle by considering some kinds of disturbances. The PI controller is designed for a liquid level model under H∞ constraint. The effectiveness of the designed PI controllers is evaluated through simulations considering disturbances.

Model construction of heat source in an OTEC pilot plant for stabilization control based on experimental data

In ocean thermal energy conversion (OTEC) plant, electricity is generated by heat energy from temperature difference between warm seawater at surface and cold seawater in depth. OTEC plants have an evaporator as one of the most important devices. Indeed, the evaporator evaporates the working fluid to rotate the turbine connected to the generator. In this research, a model of heat source system in an OTEC pilot plant for stable operation of the plant is constructed. In the OTEC pilot plant, the evaporation of the working fluid is realized by warm water from a boiler. Therefore, it is important to keep the temperature of warm water constant. Since the temperature of warm water can be changed by manipulating the valve opening, first order models to describe the relationship between the temperature and the valve opening are constructed based on experimental data. The effectiveness of the constructed models was verified through simulation.

An improvement on LQG controller for liquid level control of separator in an OTEC experimental plant using Uehara cycle

This research proposes an improved controller design methodology for liquid level control of separator in an ocean thermal energy conversion (OTEC) plant using Uehara cycle. In the previous research, the control system design for liquid level control of separator was conducted based on the LQG control theory with state estimation via stationary Kalman Filter. However, it is verified by the simulation of this research that an assumption on an integral degrades the estimation accuracy of a state variable. To cope with this problem, in this research, the reset of integration is introduced to the control system. The usefulness of the proposed method is confirmed through simulation.

Evaluation of a liquid level model of separator in an OTEC experimental plant using Uehara cycle via different experimental data

This research is concerned with the evaluation of a liquid level model of separator in an ocean thermal energy conversion (OTEC) plant using Uehara cycle. The liquid level model is described by the polynomial of valve opening and white Gaussian process. The mean and the variance of white Gaussian process are determined by two kinds of experimental data. The behavior of the liquid level model is evaluated by numerical simulations based on two kinds of experimental data. The simulation results indicate that the model construction of liquid level can ben successfully conducted even if the experimental data to be used are different.