Multiple model disturbance rejection predictive control of main steam temperature

There are many factors affecting the stability of the main steam temperature (MST) in thermal power plant operation due to its complex structure. Variations of the main steam flow and boiler combustion condition are all possible disturbances affecting the stability of the MST, and further threatening the safety and economy of the entire power plant. Conventional model predictive control (MPC), because of its lack of disturbances modeling, often fails to reject unknown disturbances caused by uncertain disturbances such as coal quality variations in the fuel gas side. To solve this problem, this paper proposed a multiple disturbance model predictive control (MDMPC) for the MST system. An analytical superheater model was first established, and then a local state space model was derived at the rated load and was used in simulations. It proves that MDMPC is equivalent to the conventional MPC when no active disturbances exist. Simulation results also demonstrate the MDMPC's successful rejection of unknown disturbances entering the MST system, which further improves the control quality of the MST system. © 2014 Chin. Soc. for Elec. Eng.