Hybrid Fuel Impact Reconciliation Method: An integral tool for thermoeconomic diagnosis

This paper proposes a method of thermoeconomic diagnosis based on the concepts of the fuel impact formula and the analytical reconciliation method. Such a method is able to detect, isolate and quantify individually the causes in terms of the additional fuel consumption, when internal malfunctions or control deviations occur. Commonly, any diagnosis method requires the definition of a Test State Condition (TEC), a Reference State Condition (REC), and a comparison technique. In the proposed method the technique is based on the reconciliation procedure, however the common factor consists in maintaining the overall production of a steady operating plant. This will determine the term-by-term fuel impact due to each malfunction. The results obtained allow a comparison between the methods mentioned earlier. The keys of the proposed method are the modification of the reference state, the integration of a modified fuel impact formula and the introduction of a filtering technique for the effects induced by the control and regulation system. In order to validate the mathematical model, this is applied to a combined cycle power plant. Comparisons between the proposed model and the results from the other two methods are studied. The diagnosis error was less than 0.2%.