An equivalents study on perturbation stability model in wind power grid based on optimal combination theory

With the improvement of the capacity of largescale wind power grid and single wind turbine, the problem of perturbation stability in wind power grid is getting more significant. A mathematical model has been deduced from the dynamic characteristics of the wind turbine, which can be used in perturbation stability analysis of doubly-fed units, including shafting model, pitch angle model, the doubly-fed machine model. The proposed Model Equivalents Method is based on the optimal linear combination theory, which can reduce the original order of the system. This method can also demonstrate the accuracy of the equivalent model according to the goodness of fit of state quantities´ dynamic characteristics before and after the order reduction.