Controllability analysis of IPM generator connected through LCL filter to the grid

The components of renewable energy systems including interfacing filters are first selected to ensure steady optimum performance operation, after which controllers are designed and implemented to ensure stability, high dynamic performance and robustness to disturbance and parameter variations. Sometimes, the component selection made, such as the structure and values of the elements of the filter may adversely affect or limit controller performance. In order to prevent or to be aware of this possibility, the controllability analysis of the open-loop system which reveals the inherent characteristics of the system is desirable. In this paper the controllability analysis of an interior permanent magnet (IPM) wind turbine generator connected to the grid through a filter interface is studied. The stability of the nonlinear system and the study of the zero dynamics provide insights into potential constraints on controller structure and dynamics. It is revealed, for the selected controlled variables that the LCL filter makes the system to have unstable zero dynamics, which pose a limitation on controller structure that can be used and its dynamic performance.