Study on linear dynamic model and analysis of operating characteristics of high-power VSCF wind energy conversion system

This paper presents a global linear dynamic model and analysis of operating characteristics for a wind power system. Which uses a variable speed wind turbine (VSWT) driving a squirrel-cage induction generator (SCIG) connected to a grid. The fifth-order precise model including wind speed, wind turbine, SCIG, drive train system, power converter and grid is obtained through segmentation method firstly. Then the third-order simplified model using the voltage of stator winding and the wind speed as control variables is established in the rotating coordinate system of stator rotating magnetic field. The reduced-order model is obtained by employing singular perturbation method. Finally, linearization, eigenvalue analysis and simulation are conducted in MATLAB/SIMULINK. The comparison of transient behaviors of the state variables in response to wind speed step changes and the stator voltage (q component) step changes is made for the third-order simplified model vs. the fifth-order precise model in detail. The results prove that the proposed model has good accuracy. Moreover, the third-order simplified model can be used to replace the fifth-order precise one for the high-power wind energy conversion system based on SCIG. Thus, not only the design of control system for wind power generation system can be realized more effectively, but also the analysis of operating mode in a variety of dynamic behavior can be made more easily.