Mathematical Representation of WECC Composite Load Model

Composite load model of Western Electricity Coordinating Council(WECC)is a newly developed load model that has drawn great interest from the industry.To analyze its dynamic characteristics with both mathematical and engineering rigors,a detailed mathematical model is needed.Although composite load model of WECC is available in commercial software as a module and its detailed block diagrams can be found in several public reports,there is no complete mathematical representation of the full model in literature.This paper addresses a challenging problem of deriving detailed mathematical representation of composite load model of WECC from its block diagrams.In particular,we have derived the mathematical representation of the new DERA model.The developed mathematical model is verified using both MATLAB and PSS/E to show its effectiveness in representing composite load model of WECC.The derived mathematical representation serves as an important foundation for parameter identification,order reduction and other dynamic analysis.