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Fault-Tolerant Control Strategy Based on Reliability and Cost Analysis in Heat Recovery Steam Generator Plant

Heat recovery steam generator (HRSG) is an equipment part of the combined cycle power plant (CCPP), which consists of the gas turbine, HRSG, and steam turbine. HRSG performs a significant role in defining the efficiency of the CCPP. The fault condition at a subsystem or component of HRSG could cause failure in entire CCPP systems. Therefore, the fault potential should be identified, and the failure should be mitigated once it occurs. The objective of this study is to determine the alternative control structure which can be applied in the HRSG system in case of major fault and to determine which the most optimum alternative control structure based on reliability and cost analysis. First, the fault is determined and ranked based on the severity of the effect. Restructuration will be done for any major fault with severity rank 8 and above. The alternative control structure will be determined, then reliability and cost analysis will be applied to those structures to choose the most optimum alternative structure which will be applied in the system. Modeling and simulation will be done using MATLAB Simulink. Closing the blowdown valve, reducing the opening of the steam outlet control valve, and the combination of the previous two structures are the alternative structures that can be applied in HRSG systems in case of complete loss in the economizer outlet control valve. The third structure is the most optimum alternative structure based on a reliability and a cost analysis. It has reliability rate of 3.99 and cost of $12,078.87. The third structure also has the longest retention time of 436 s.