The paper presents a feedback control of Linear Quadratic Regulator (LQR) scheme for Selective Catalytic Reduction (SCR) process in combined-cycle (CC) power plants. The SCR process is to reduce NOx emission at the CC power plants, prior to venting into the atmosphere by decomposing process using Ammonia (NH3) at the SCR catalysts. This process can be considered as a nonlinear with time delay system. To improve the process efficiency, we are proposing cascade structure of feedback control system which consists of NOx control and NH3 control that are designed with LQR scheme. A multi-rate sampling system is adopted in the cascade design to cope with a slow SCR process, and a fast NH3 injection system characteristic. Furthermore, the structures of the controllers are designed to be implemented in the power plants control system. Simulation results on actual power plants conditions shows a satisfied control performance and design practicability.
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