Sequential Distributed Development of Multiple Retrofit Controllers: Independence of Identification, Design, and Operation

Abstract

This paper is concerned with sequential distributed development of multiple retrofit controllers that are managed by respective controller designers. Retrofit control is a modular control approach for stable network systems whose subsystems are controlled by their corresponding local controllers. From the standpoint of a single controller designer, the subsystems managed by all other designers can be regarded as an unknown environment, an approximate model of which is supposed to be accessible in local controller design. This paper shows that, for the identification of approximate environment models, each of all environments for controller designers are invariant with respective to all design parameters in retrofit controllers. Furthermore, it is also shown that, for the entire feedback system, control performance regarding a local evaluation in response to a local disturbance is improved as improving the accuracy of a corresponding approximate environment model, while control performance regarding a global evaluation is not in general. The significance of the theoretical results is verified through an example of power systems control.