A comparison between model reduction and controller reduction: application to a PWR nuclear plant

In our previous paper (1998), we compared model reduction, in both open and closed loops, with closed-loop identification of a low-order model. Both methods were applied to the design of a controller for the secondary circuit of a nuclear pressurized water reactor (PWR), leading to the conclusions that system identification is a viable alternative to model reduction, and that the key feature for a successful control design is not so much the choice between order reduction or identification, but between open-loop and closed-loop techniques. In the present paper, we go further in this study and we compare model reduction with controller reduction for the same PWR system. We show that closed-loop techniques are more powerful than open-loop ones, and that controller reduction gives better results than model reduction when appropriate frequency weighting are chosen.