PI controller design of grid-side PWM-regulated ac/dc converters via stability analysis based on passivity

PWM-regulated ac/dc converters are of great importance in distributed power system applications since they are widely used to interface a variety of renewable power sources such as wind and photovoltaic generators with the grid. Furthermore, they provide special control possibilities of the active and reactive power. In this paper, a new stability analysis and design approach for nonlinear PI controllers for this kind of devices is proposed, based on the passivity analysis of the complete system. To this end, first the nonlinear model of the system is obtained, on which suitably modified PI controllers are incorporated. The analysis conducted provides a set of limits, rules and demands that should be satisfied in order to achieve fast, accurate and satisfactory responses. Furthermore, it is proven that, in all cases, a closed-loop system with desired damping is guaranteed while the controllers' dynamics drive the system at the reference values. The simulation results indicate the effectiveness of the controller design.