Damage modeling and life extending control of a boiler-turbine system

The main idea in life extending control (LEC), also known as damage mitigating control, is to redesign the controller in order to achieve a better tradeoff between structural durability and dynamic performance in a system. This task involves both damage dynamics modeling and LEC design. In this paper, we propose a new hierarchical LEC structure and apply it to a typical boiler system. There are two damage models in this structure: Model I is for online LEC and Model II is for online life prediction for critical components of the system. For Model I, we incorporate the improved rainflow cycle counting method and a continuous-time damage modeling approach. While for Model II, we choose a method based on the P-K theory which involves the mean stress effect. Finally, an optimal LEC scheme is proposed and simulation results show that the designed LEC substantially reduces the accumulated damage with a minimum loss of dynamic performance.