On the observability of the flying capacitor converter

This paper addresses the continuous state estimation of a class of switched systems having modes in which the state is not fully observable. Using a suitable LaSalle principle for switched systems, we give a characterization of invariant sets and associated switching laws for which the state cannot be estimated. This result is applied to a flying capacitor converter in order to prove the convergence of the estimation error under a wide class of switching laws. The characterization of invariant sets is also used to explain why the convergence rate of the estimation error decreases as the switching frequency increases.