Robust state feedback control applied to a UPS system

This paper addresses the problem of robust control design for a single-phase uninterruptible power supply by means of state feedback. Sufficient conditions are given for the existence of a robust stabilizing control gain that assures: a) the closed-loop system pole location inside a circle on the left-hand of the complex plane if the load is considered as an uncertain time-invariant or slow time-varying parameter; b) at least the stability of the closed-loop system if the load is considered as an arbitrary time-varying parameter. The robust control conditions are formulated in terms of a set of linear matrix inequalities easily solved using specialized softwares. Design examples and simulation results illustrate the method proposed.