In the previous work, several procedures for simultaneous tuning of PID gains have been applied to an industry-standard nonlinear six PID-type controllers cluster in the closed loop. The cluster was controlling 4-input-7-output nonlinear power plant model with time-delay representing sufficiently well a typical coal-fired boiler/turbine system. Although satisfactory time domain performance was achieved, it was discovered through closed-loop linearization that the closed-loop performance robustness of the original model under the standard PID cluster around operating points is rather poor and can be only marginally affected through tuning, implying that a well-tuned cluster would require retuning under not very significant changes in plant parameters to maintain adequate performance. In order to investigate whether the power plant model used admits the closed-loop performance that is more robust to changes in plant dynamics, an applicability of full-rank linear∞ controller design for this system is assessed. For this purpose, the system is linearized, the time delay elements are replaced by their 4th order Pade approximations, and the controllability and the observability of the resulting linear plant model approximation are established, showing the full-rank linear H∞ controller design to be applicable to this system. The details of the latter design for the linearized system are presented, and the closed loop with the resulting controller and the linearized plant model is shown to attain an order of magnitude higher robust performance measure than that attained under the linearized standard PID cluster. The time domain performance of the closed-loop system with this H ∞ controller and the original plant model is simulated as well and is found to be satisfactory in a wide range of load changes. It is also shown by simulation that the closed-loop performance of the original model with the PID cluster significantly degrades under a typical plant model perturbation, while the latter virtually has no effect on the performance of the closed loop with the original model and the H∞ controller.