Advanced control of power electronic systems

Abstract

Power electronic systems (PESs) are nonlinear hybrid dynamical systems [1]. The instability in such switching systems, owing to their discontinuity, can evolve on slow and on fast scales [2]. Conventional analyses of PESs and their subsystems are based on averaged models, which ignore the fast-scale instability and analyze the stability on a reduced-order manifold [1-3]. As such, validity of the averaged models varies with the switching frequency even for the same topological structure. The prevalent procedure for analyzing the stability of standalone and networked PESs is based on linearized averaged (small-signal) models that require a smooth averaged model. Yet there are systems (in active use) that yield a non-smooth averaged model. Even for systems for which smooth averaged model is realizable, small-signal analyses of the nominal solution/orbit do not provide anything about three important characteristics: region of attraction of the nominal solution, dependence of the converter dynamics on the initial conditions of the states, and the post-instability dynamics. As such, conventional linear controllers for PESs, designed based on small-signal analyses, may be conservative and may not be robust and optimal.