Robust wide-range control of electric power plants

Automatic control plays a key role in the continuous search for enhanced safety and operational performance of electric power plant operations. Currently, daily cycling of large generating units that were designed for baseload operation is an economic necessity. Consequently, the power plant control system is required to have high maneuverability.; In this dissertation, a methodology for synthesizing the integrated feedforward-feedback control (FF/FBC) strategy is proposed for wide range robust control of commercial scale steam-electric power plants. In the proposed method, the feedforward control (FFC) law is generated via nonlinear programming for simultaneous optimization of all control inputs; the feedback control (FBC) law is synthesized by the H{dollar}sbinfty{dollar}-based structured singular value ({dollar}mu){dollar} approach to achieve the desired stability and performance robustness. To exemplify the proposed methodology, an FF/FBC system is synthesized for a 525 MWe fossil-fueled electric power plant. The synthesis of the FFC policy is identified as an optimization problem where the performance is characterized by rapid change of electric power while maintaining the throttle steam temperature and pressure, and the hot reheat steam temperature within small ranges of variation. The FBC synthesis is posed as a multivariable control problem where the objective is to achieve robust stability and robust performance under specified performance criteria and uncertainty bounds which represent errors due to linearization of the nonlinear plant model, unmodeled dynamics, and inaccuracy of the plant model parameters.; The efficacy of this control synthesis methodology was investigated by simulation experiments in which the synthesized FF/FBC law was applied to control the nonlinear model of the power plant. Simulated disturbances, representing modeling error and parametric uncertainties, were injected into the control system to investigate the robustness properties. The simulation results suggest that the FBC is capable of rejecting the anticipated disturbances such that the plant would closely follow the optimal trajectory determined by the FFC law.