Integrated operation design and control of Organic Rankine Cycle systems with disturbances

Traditionally, the control design of Organic Rankine Cycle (ORC) is sequential. The operating condition is obtained first by steady-state optimization, and then the controller is designed around the operating condition. Since the fluctuating nature of the heat source is not considered in the design of operating conditions, it is easy to violate the constraints of the ORC system during the operation. It is, therefore, of paramount importance to integrate the closed-loop dynamic performance analysis into the design of operating conditions to make sure the dynamic feasibility. An integrated design and control approach of the ORC system is proposed based on the mechanistic nonlinear model of the ORC system. It maximizes the waste heat recovery and guarantees the safe operation in the presence of disturbances. The optimal operating conditions and the controller parameters are obtained simultaneously through a nonlinear constrained optimization problem. The performance comparison between the integrated design and control approach and the sequential control design reflects the advantages of the proposed integrated approach. Its results with different control strategies (PI controllers with static feed-forward and PI controllers without static feed-forward) show that a well-behaved controller can improve heat recovery and the effectiveness of the proposed method.