Life-extending control of fossil fuel power plants

Abstract

The objective of life-extending control is to achieve a trade-off between structural durability and dynamic performance. This paper focuses on structural durability of the main steam header under load following to illustrate how the life-extending control of fossil fuel power plants can be achieved via feedforward/feedback. This concept is potentially applicable to both new and aging power plants under a variety of operational modes such as hot start-up, scheduled shutdown, and load following where the plant power is rapidly maneuvered to meet the varying load demand. The feedforward control policy is synthesized via nonlinear optimization of a multi-objective cost functional of dynamic performance and service life under the constraints of actuator saturation, operational limitations, and allowable structural damage, including thermomechanical fatigue and plastic deformation. A linear robust feedback control law that is superimposed on the feedforward sequence is synthesized based on induced L 2-norm techniques. The results of simulation experiments are presented to demonstrate that the proposed feedforward/feedback control policy is potentially capable of ramping the plant power up at a rate of 10% of the full load per minute while maintaining the specified performance and satisfying the damage constraints.