Feedforward compensated multiloop control of a power plant

Most control systems for fossil-fuel power plants basically consist of multiloop configurations of PID-based feedback control loops complemented with many feedforward compensations, which have been added to minimize the effects of interaction among the control loops due to the coupled process dynamics. Many configurations have been developed after various decades of research and practical experience. Currently, the required feedforward compensations are not designed in a systematic way, but heavily depending on the designer's experience. This paper presents a first evaluation of a multiloop control scheme with a feedforward-equivalent compensator, which can be designed from input-output process data. Placed between the controllers and the process, the purpose of the compensator is to reduce the control loop interaction effects to a degree manageable by the controllers. The compensator is built in such a way that the direct control loop paths are preserved: interaction compensation factors are added among the control signals. The compensation factors are determined from steady-state input-output process data; neither a dynamic model of the process, nor the solution of an optimization problem are required to design the compensator. Analysis and simulation experiments show that the proposed compensation is numerically well-conditioned, and effectively handles control loop interaction.