Lyapunov Stability Analysis of Thyristor Inverter System

A single-phase bridge inverter system is analyzed. It is assumed that the inverter output voltage waveform is pulse-width modulated to control the system voltage. The system involves a closed-loop control containing a pulse modulator supplying a general filter. A feedback signal which is a function of the filter output is compared with a reference constant to deliver the error signal which determines the pulsewidth. A modified Lyapunov theorem on bounded-input bounded-output (BIBO) stability is used in the stability analysis of the discrete state equations for the system. Sufficient conditions for BIBO stability are derived. The results are verified by a digital computer simulation of the system. Systems with linear parts that have distinct or repeated eignvalues that are either real or complex may be analyzed using this method.