Plant-wide Control for Fuel Processor System with PEM: Control structure selection and optimal sensor location

Abstract

The synthesis and a plantwide control strategy based on the process knowledge for the fuel processor with fuel cell were detailed in chapter 9. There, the units dimensions and the equipment interconnections were defined to conform the flowsheet of the complete process at the more efficient operating point . The knowledge based plantwide control strategy was tested through the control-oriented dynamic model in chapter 10. In this chapter a new systematic and generalized procedure is applied to simultaneously solve the optimal sensor placement integrated to the plantwide control design. This methodology allows configure the loops pairing by considering the trade-off between servo and regulator behavior. It can be done thanks to define a proper function, named net load effect, accounting both set point and disturbances effects. Even though some concepts used in this approach are not new, the main contribution of this method is the selection of the adequate objective function. It is mathematically expressed in a new way, in terms of Frobeniusnorm of specific matrices related with the reduced models of the plant and very useful for evaluating the process interaction. Then, it drives the search supported by genetic algorithms (GA), which evaluates all the possible combinations of inputoutput variables. It allows to solve successfully and with less computational effort the combinatorial optimization problem, even though the high dimension usually involved in large scale chemical plants. It must be emphasized that this approach is developed for working in cases where only steady-state plant information is available.However, if a dynamicmodel is disposable too the algorithmis extended to use it. In addition, a mathematical demonstration is presented so as to understand why is possible through the proposed sequence of calculations to find a well conditioned control structure. This methodology has been successfully tested on several well known benchmark cases of chemical plants. Hence, in this chapter it is applied to the challenging and novel case of the fuel processor with fuel cell. Thus, through a set of dynamic simulations for different scenarios it can be shown the high capacityof this approach.