Adaptive fuzzy finite time integral sliding mode control of the coordinated system for 350 MW supercritical once-through boiler unit to enhance flexibility

The flexible operation of supercritical once-through boiler (OTB) units must be improved to undertake more clean energy generation. First, because of the strong coupling and nonlinearity of the OTB unit, the unit model was accurately linearized using the mathematical concepts of Lie derivatives and relative orders. Subsequently, the finite time integral sliding mode control (FTISMC) strategy was developed. Notably, the maximum relative tracking errors for the main steam pressure, separator steam enthalpy, and active power at a load ramp rate of 6 % RBL/min based on the FTISMC strategy were only 0.065 %, 1.85 % and 35 % of those under the stair-like generalized predictive control (GPC) with feedforward strategy at a load ramp rate of 2.21 % RBL/min. Lastly, unlike previous work, the adaptive fuzzy finite time integral sliding mode control (AFFTISMC) strategy was employed to address both input and output disturbances, and the maximum dynamic errors of the main steam pressure, separator steam enthalpy, and active power do not exceed 1.4 %, 1 %, and 63 % of the FTISMC strategy. Therefore, the AFFTISMC strategy substantially enhances the flexible operation capability of the unit, offering valuable insights for optimizing the coordinated control system (CCS) of thermal power units to facilitate greater absorption of new energy electricity.