The complex Hurwitz test for the stability analysis of induction generators

The paper proposes a new approach for the analysis of stability of induction generators. A PI-controlled doubly-fed induction generator is considered. The new method is based on a Hurwitz test for polynomials with complex coefficients. Using the test, stability of the PI controller is found to be guaranteed if a simple quadratic inequality relating the proportional and integral gains of the controller is satisfied. The application of the complex Hurwitz test is also demonstrated on another example. The method provides a new, systematic procedure for stability assessment and control design in induction machine problems.