Robust controller design for simultaneous control of throttle pressure and megawatt output in a power plant unit

Abstract

SUMMARYThis paper presents an application of H and -synthesis controller design methods to a coal-"red power generation unit and compares the closed-loop performance and robustness of H and -synthesis control laws with those of an H control law. The model which relates "ring rate and turbine valve position inputs to throttle pressure and megawatt outputs presented by Ollat and Smoak in an earlier work is modi"ed to match the test data from a Tennessee Valley Authority (TVA) power generation unit. All three controller synthesis procedures are applied to a two-input two-output plant model which has time delay, di!erential part, colored noise output disturbance, and sensor noise disturbance. Application of the procedures to the model shows that when the shape of the closed loop control signals of all three designs is closely matched, in the low-frequency range the -synthesis and H control laws have robustness much better than that of H control law, while providing adequate robustness in the high-frequency range. H control law gives the best performance, and H } the worst of the three designs, exhibiting the largest overshoot. The balancing procedure permits signi"cant reduction of the order of the controllers without degradation in performance and robustness. The comparative evaluation of three designs shows that in power plant control problem H and -synthesis designs provide much more consistent and convenient performance/robustness trade-o! than H design.

Optimal control of coal-fired power plants using a LMI formulation

“…Similar to the work by [8] and [9], a linear model has been obtained using black-box identification applied to input-output signals obtained from a nonlinear simulator of a 125 MW coal-fired power plant with natural circulation drum boiler. This model reflects the behavior of the plant around the usual operating point (load = 122 MW, steam pressure = 136 bar).…”

Robustified optimal control of a coal-fired power plant

“…Besides inserted this way, the Q parameter does not modify the initial Input/Output (I/O) transfer but it modifies the sensitivity function offering a possibility to increase the robustness of the initial controller. As Q belongs to an infinite space, a sub-optimal solution is to use a polynomial or a FIR (Finite Impulse Response) filter [7], [11] in the state-space formulation (5).…”

“…1 A high-level model of the plant, with coal flow and turbine valve opening as inputs and load and steam pressure as outputs is considered (this assumes that all other local control loops are in place). Similar to [4] and [5], a linear model has been obtained using black-box identification applied to input-output signals obtained from a nonlinear simulator of a 125 MW coal-fired power plant with natural circulation drum boiler. This model reflects the behavior of the plant around the usual operating point (load = 122 MW, steam pressure = 136 bar).…”

Optimal switching control of burner setting for a compact marine boiler design

“…Especially for control of the continuous parts of the dynamics many advanced methods have been proposed-see e.g. Mortensen, Mølbak, Andersen, and Pedersen (1998), Zhao, Li, Taft, and Bentsman (1999), Lee, Kwon, and Kwon (2000), Kothare, Mettler, Morari, Bendotti, and Falinower (2000), and Rossiter, Neal, and Yao (2002).…”