Dynamic analysis of PI controllers applied on AC/DC grid-side converters used in wind power generation

The control features of the ac/dc grid-side converters used to connect wind power systems with the grid are of significant importance for the overall grid performance. In this paper, the conventional PI controllers used in cascaded structure to regulate the dc voltage and the system power factor are analysed by using the well-known linear control theory. An alternative analysis, namely a nonlinear passivity based analysis, is conducted that results in some significant innovations for the controllers´ design. These innovations lead to a simpler controllers´ form than the conventional one since as it is proven, exact cancellation of the cross-coupling terms of the system as well as cancellation of the grid voltage component through the controllers´ design are not required. The simulation results verify the proposed design approach since it enhances the system robustness and response.