Stable parameter-free nonlinear controller for AC/DC voltage source converters

In this paper, a novel nonlinear dynamic regulator for three-phase AC/DC voltage source converters (VSC) is presented. The proposed control design approach is fully independent from the system parameters and simultaneously achieves precise DC bus voltage regulation and unity power factor operation. A traditional PI controller is used to achieve unity power factor, while the proposed nonlinear controller is used to regulate the DC bus voltage to the desired level. Due to the structure of the proposed scheme, closed-loop system stability is proven and an appropriate mathematical analysis shows that the solution remains bounded and converges to the desired equilibrium. Simulation results verify the controller efficiency under DC bus voltage reference and load changes.