Robustness enhancement of PID cluster for a nonlinear power plant model with time delay

Shu Zhang, Joseph Bentsman, Cyrus W. Taft

Research output: Chapter in Book/Report/Conference proceedingConference contribution


Proportional-integral-derivative (PID) controllers have been widely utilized in power plant system as dominant control strategy for the past decades. 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 that through closed-loop linearization the closed-loop robustness performance of the original model under the standard PID cluster around operating points is rather poor. This 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 this paper, A consistent robustness enhancement procedure is proposed to correct the main structural deficiencies of the existing cluster by introducing into it additional control elements, for example - off-diagonal proportional links, based on full-rank linear H controller design, to approximate the robustness performance of the latter. The simplest nonlinear PID cluster robustification is presented. This type of PID cluster redesign could be easily implemented using the existing software/hardware control equipment. The closed-loop system consisting of the original and the robustified PID clusters with the original plant model is simulated respectively. The simulation results have shown that the closed-loop performance of the original model with standard PID cluster significantly degrades under a typical plant model perturbation, while the latter has much smaller effect on the performance of the closed loop with the original model and the robustified PID cluster.

Original languageEnglish (US)
Title of host publication55th ISA POWID Symposium 2012
Number of pages21
StatePublished - 2012
Event55th ISA POWID Symposium 2012 - Austin, TX, United States
Duration: Jun 3 2012Jun 8 2012


Other55th ISA POWID Symposium 2012
Country/TerritoryUnited States
CityAustin, TX

ASJC Scopus subject areas

  • Energy Engineering and Power Technology


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