(640c) Supervisory Predictive Control of An Integrated Wind/Solar Energy Generation and Water Desalination System: A Two-Time-Scale Approach

Renewable energy sources, for example wind and solar energy, are attractive choices for providing energy to reverse osmosis (RO) desalination systems for small communities in remote areas and isolated islands that have access to sea or brackish-water. Many studies have been done on the integration of renewable energy generation systems with RO desalination systems including wind-powered and solar-powered desalination systems.

However, the combination of renewable energy sources and water desalination systems requires addressing challenges in the operation of the integrated systems. Specifically, unexpected drops in energy production of a solar or wind energy system may require quick start units to cover the shortfall while unexpected increases require the ability to absorb the unscheduled generation. One way to deal with the variable output of wind and solar energy generation systems is through the use of integrated energy generation systems using both wind and photovoltaic energy, which are also tightly integrated with distributed energy storage systems (batteries) and controllable energy loads like; for example, a water desalination system that operates at controllable time intervals to meet specific demand.

In our previous work [1], we proposed a supervisory predictive control method for stand-alone wind-solar energy generation systems in which the supervisory control system was designed via model predictive control (MPC) to take into account optimal allocation of generation assignment between the two subsystems. However, little attention has been given to the optimal operation and control of integrated wind-solar energy generation and RO water desalination systems.

In the present work, we re-design the supervisory MPC in [1] to satisfy specific requirements for the control of a stand-alone hybrid wind-solar energy generation system which provides power to a RO membrane water desalination system. The primary control objective is to coordinate the wind and solar subsystems as well as a battery bank to provide enough energy to the RO system to satisfy the power demand of the scheduled water production. In the supervisory MPC, a specific cost function is designed to take into account the desired control objective. Simulations are carried out to illustrate the applicability and effectiveness of the proposed design.

[1] W. Qi, J. Liu, X. Chen, and P. D. Christofides, "Supervisor predictive control of stand-alone wind-solar energy generation systems," IEEE Trans. Contr. Syst. Techn., in press.