In recent years several concepts and tools for modelling and simulation of nonlinear heterogeneous and multi-domain systems have been developed, speeding up to a great extent the process of an accurate analysis by simulation of increasingly complex technological systems. In parallel, for dimensioning and, above all, for control system design purposes, the need of models of reduced complexity has emerged, together with the need of tools capable of extracting, from the overall dynamic model, reduced models, representing the dominant behaviour. The paper reviews recent results in nonlinear model order reduction, originally developed with reference to computer aided analysis and design of electronic circuits, and puts them in a control syst...