A Study of Dynamic Equivalence Using the Similarity Degree of the Equivalent Power Angle in Doubly Fed Induction Generator Wind Farms

This paper presents a study of dynamic equivalence for doubly fed wind farms (DFWFs) in large power systems. The core idea is to find an attribute representing the critical characteristics of a doubly fed induction generator (DFIG) and use it for clustering in the equivalent modeling process. Using the voltage and flux linkage equations of DFIGs, we derived an electromagnetic power expression. Similar to the power angle concept for synchronous generators, an equivalent power angle (EPA) is proposed and shown to represent the dynamic characteristics of a DFIG in the test system. We introduce the similarity degree of the EPA based on similarity theory and construct a similarity index of the EPA for clustering a DFWF. A practical algorithm was developed for parameter aggregation of the equivalent model. In addition, a simulation of DFWFs in Yunnan, China, was conducted to show the feasibility and high precision of the proposed method.