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

摘要

This paper presents an application of H _(infinity) and μ-synthesis controller design methods to a coal-fired power generation unit and compares the closed-loop performance and robustness of H _(infinity)and μ-synthesis control laws with those of an H_2 control law. The model which relates firing rate and turbine valve position inputs to throttle pressure and megawatt outputs presented by Ollat and Smoak in an earlier work is modified 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, differential 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 μ-synthesis and H _(infinity) control laws have robustness much better than that of H_2 control law, while providing adequate robustness in the high-frequency range. H _(infinity) control law gives the best performance, and H_2 - the worst of the three designs, exhibiting the largest overshoot. The balancing procedure permits significant 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 _(infinity) and μ-synthesis designs provide much more consistent and convenient performance/robustness trade-off than H_2 design.