Analysis and control of a cascaded doubly-fed induction generator

Due to the recent interest in renewable energy systems (windmills, small-scale hydropower) and embedded applications (more electric aircraft and vehicle), control of variable speed constant frequency (VSCF) generators has become a very important research topic. Among the possible types of VSCF generators, a good candidate is the cascaded doubly-fed induction generator (CDFIG). This brushless robust structure is also driven by a low power converter in comparison to the power provided to the grid. However, because of its inherent complexity, an efficient control design methodology is needed. The presented paper proposes to establish a rigorous design methodology based on the inversion of the dynamical model of the system. It also uses an original representation of the system called dynamical equivalent circuit. This method has been successfully applied to two cases: a CDFIG connected to a utility grid and a CDFIG connected to an isolated grid in the presence of a significant amount of nonlinear load.