Phase compensation based active disturbance rejection control for high order superheated steam temperature system

With the continuous penetration of renewable energies, the control requirements for conventional thermal power unit superheated steam temperature (SST) systems are gradually increasing, to cope with more frequent and large-scale load changes. As a key parameter in the thermal power generation process, SST directly affects the safe and economic operation of the unit. However, the SST system is a typical high-order, large inertia industrial process, which poses severe difficulties to improve the control performance in practice, especially the disturbance rejection performance. To this end, this paper proposes a phase compensation (PC) based low-order active disturbance rejection control (ADRC) strategy for a class of high-order, large-inertia processes. Firstly, the working principles and control problems of SST system are illustrated, and the SST model is identified based on the open-loop step experiment data. Then, the phase compensation network model is derived in detail by low-frequency approximation. A design shift is presented, PC is adopted to compensate process dynamics and obtain reduced-order plant equivalently, which makes it also accessible to other error-based controllers. For engineering practice, its simple implementation and equivalent plant analysis for PC-ADRC control system are also given. At last, the stability and robustness of the PC-ADRC control system are carefully studied. The PC-ADRC controller parameters are determined according to the ideal dynamics and the trade-off between the performance and robustness. Both analysis and simulations show that the PC can effectively improve the robustness and fast response ability of high-order process control system. The efficacy of the proposed method is verified by simulation results based on the identified model, and a laboratory experiment shows the promise in practical applications.