Mechanical Analogous Model of Wind Turbine Generators for Grid Connection Studies

Mechanical analogous model of Conventional Synchronous Generator (CSG), Fixed-Speed Induction Generator (FSIG) and Doubly-Fed Induction Generator (DFIG) are developed to investigate and compare the oscillatory behaviour of respective wind turbine-generators subjected to various disturbances. In this way, torque-to-current analogy and concept of mechanical impedance are employed to achieve the equations of motion. The significance of detailed representation of the various parts of the DFIG oscillatory system containing the turbine, the generator and the power electronics converters is discussed and compared with simple FSIG system by means of analyzing the governing equations. Finally, calculating the eigenvlaues of the equivalent mechanical system, the system oscillatory stability is assessed.