Optimal operation of an industrial boilerturbine system is obtained with properly control of drum pressure, drum water level and the output load (MW) parameters. In boiler system, multi loop (decentralized) proportional-integral (PI) control is used because of its implementational advantages. PI controller under normal conditions of boiler has suitable performance but by changing this normal conditions, retuning is required. An useful method to overcome this problems is using multivariable robust control. This method of designing, causes to pole zero cancelation between plant and controller at all the stable poles of the uncompensated plant, and any unstable open-loop poles reappear in the closed-loop reflected in the imaginary axis. In this paper for reaching to proper performance and robustness in boiler control system and overcome mentioned problem; bilinear transformation and H
Synthesis is used that in comparison by using common multivariable robust control, settling and rise time and damping of system is improved. In fact by using bilinear transformation, the performance of system in significant parameter control improves remarkably1.

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