Cascade IMC-PID Control of Superheated Steam Temperature based on Closed-loop Identification in the Frequency Domain

This paper proposes an IMC-PID Cascade Control of Superheated Steam Temperature based on closed-loop identification in the frequency domain. The process models of superheated steam temperature are firstly identified with set-point change tests in the inner and outer control loops. The process frequency responses are estimated, and then transform functions are obtained by least square method in both amplitude and phase. The IMC-PID controllers of the Steam Temperature Cascade Control loop (SST) is designed by using the internal model control (IMC) and improved Skogestad-IMC (SIMC) method based on the obtained model. It is shown that this control strategy achieves better control performance and minimizes the effects of external and internal disturbances.