In order to ensure multivariable industrial processes operating in a safe and economic mode, a method for control performance assessment of hierarchical control systems was proposed. The three-layer structure of a hierarchical control system: direct control layer, constraint control layer and real-time optimization layer, was analyzed to formulate the control objective functions of three aspects: suppressing disturbances, keeping constraints and maximizing process profits, respectively. A control performance assessment benchmark called “best to worst performance range” was established to monitor the economic performance of industrial processes, and to evaluate how much potential would be improved. To avoid the degradation of control performance due to model-plant mismatch, a method to compute generalized object model through open loop model and regulatory parameters was presented. The reliability and efficacy of the proposed performance assessment technique is demonstrated on a case study on Shell heavy oil fractionator control problem.
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