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Abstract: In this paper, a practical method to design a robust controller for pressure of boiler in Mashhad Power plant using H∞ is proposed. To achieve a good performance of an industrial boiler in order to reduce fuel consumption rate and reaching higher efficiency, dynamic variables such as fuel flow, air flow and pressure of boiler must be controlled. However this dynamic model may associate with uncertainties. Uncertainties in mentioned model are caused by lack of knowledge about the dynamics of the system, pay load changes, and air flow. Thus, application of robust control methods for high precise control of pressure is inevitable. In the first step plant is identified by using experimental data by the mean of converting into a group of linear time invariant (LTI) uncertain plants. After representation of the uncertain dynamic system in general control configuration and modelling the parametric uncertainties, nominal performance, robust stability and robust performance against disturbances are analyzed by the concept of structured singular value μ. Then, using genetic algorithm an optimal controller is designed for tracking problem and disturbance rejection. This procedure gives a satisfactory controller at the presence of model perturbations. For more comparisons, quantitative feedback theory (QFT) as a well known robust control approach is also applied to the plant. Finally, nonlinear simulation has been carried out and two controllers are compared. Both optimal robust controllers guarantee robust performance of the system against the uncertainties and result in desired time responses of the output variables. By applying H∞ robust control, system tracks the desire reference inputs in a less time and with smoother time responses. [Copyright &y& Elsevier]

Abstract: A computational study to assess the performance of different gas turbine plants is presented in this paper. The work includes the effect of relative humidity, ambient inlet air temperature and types of fuels on gas turbine plants. Investigation also covers economic analysis and effect of fuels on emissions. Gas turbine frames of various ratings are used in gas turbine power plants in Saudi Arabia. 70 MWe GE-6101FA and 40 MWe GE-6561B frames are selected for the present study. GT PRO software has been used for carrying out the analysis including; net plant output and net efficiency, break even electricity price, break even fuel LHV price, carbon emissions etc., for a given location of Saudi Arabia. The relative humidity and ambient inlet air temperature have been varied from 30 to 45% and from 80 to 100° F, respectively. Fuels considered are natural gas, diesel and heavy bunker oil. Simulated gas turbine plant output from GT PRO has been validated against an existing gas turbine plant output. It has been observed the simulated plant output is less than the existing gas turbine plant output by 5%. Results show that variation of relative humidity does not affect the gas turbine performance appreciably for all types of fuels. For 70 MWe frame, for a decrease of ambient inlet air temperature by 10°F, plant net output and efficiency have been found to increase by about 5 and 2%, respectively for all fuels. More specifically, plant net output and efficiency for natural gas are higher as compare to other fuels. For given 70 and 40 MWe frames, break even fuel price and electricity price have been found to vary from 2.03 to 2.54 US$/MMBTU and from 0.021 to 0.0254 US$/kWh respectively. It has been noticed that turbines operating on natural gas emit less carbon relatively as compared to other fuels. [Copyright &y& Elsevier]