Prediction-based feedforward control of superheated steam temperature of a power plant

Abstract

Abstract A novel feedforward-feedback control scheme for superheater steam temperature in accordance with industrial requirements is proposed. The novelty lies in the design of the feedforward compensator (FFC), of which the performance relies on accurately predicting the values of disturbance variables. The heat influx from the flue gas and the superheater inlet steam temperature were identified as two major disturbances, in addition to the change in the power load. Two FFCs were designed to accommodate the individual disturbances. Because the flue gas state is difficult to measure, the superheater pipe temperature was chosen as a new variable to represent the flue gas state and estimated using steam temperature measurements. Both FFCs computed the feedforward inputs based on the predicted values of the disturbance variables. The prediction accuracies of the FFCs were assessed separately using field-test data, and the performance of the resulting feedforward-feedback controller was investigated through numerical simulations. As a consequence, the IAE (integrated absolute error) under the proposed control scheme was observed to be decreased by 25–38% for three load change scenarios compared to that under the existing feedback controller.