Nonlinear stability analysis for ac/dc voltage source converters driven by PI current-mode controllers

Voltage source converters operating under current-mode controllers perform a standard and extremely common scheme in many industrial applications. In this paper, the open problem of designing and analyzing such nonlinear systems is addressed. To this end, a novel passivity-based stability analysis is developed that takes into account the accurate entire nonlinear model of the system with the proposed current-mode proportional-integral (PI) controllers selected to be independent from the system parameters. In particular, a new sequential method is developed that provides the suitable Lyapunov function for the entire closed-loop system. Using this Lyapunov storage function input-to-state stability is proven; moreover, exploiting some new advanced nonlinear methods, it is shown that convergence of the closed-loop system states to the desired unique equilibrium is guaranteed. Simulation results verify the theoretical analysis providing a very good transient response and convergence to the desired steady state.