Control oriented low order modelling of a complex PWR plant: a comparison between open loop and closed loop methods

The classical way of obtaining a low order model-based controller for a high order system is to apply closed loop reduction techniques to an accurate high order model or controller of the plant. The recent literature on identification for control has promoted the idea that an alternative way is to directly identify a low order model using a control-oriented identification criterion, and to compute a controller from this model. In this paper we illustrate the validity of this alternative route for the design of a controller for the secondary circuit of a nuclear pressurized water reactor. In passing, this application also shows that the key feature for a successful control design is not so much the choice between order reduction or identification methods, but between open loop and closed loop techniques.