Study On Induction Machine VBR Model In Wind Generator Short Circuit Calculation

Various induction machine models are introduced in this thesis, especially the Voltage-Behind-Reactance (VBR) model. The major improvement of VBR model, is that the induction machine stator is represented as current controlled voltage source, and flux linkage is used as state variables, comparing with classic dq model which represent the stator as voltage controlled current source.The VBR model of squirrel cage induction machine is studied first, and its comparison with the induction machine model in popular power system simulation software, Simpower System and PSCAD is presented. The VBR model performance is validated against with classic dq model in the induction machine transient simulation, such as start up and load torque step change. Then the induction machine model including magnetizing saturation is investigated. The magnetizing current is no longer proportional with the magnetizing flux linkage during saturation. An induction machine model including saturation is proposed, which uses flux linkage as state variables. Comparing with traditional dq model, the numerical accuracy and the computational efficiency of the proposed model are improved, which is verified by the induction machine including saturation short circuit transient simulation, and the conclusion that the proposed model is more advanced in induction machine fault simulation is drawn from the comparison simulation. Finally, the induction machine model including deep bar effect is studied. The double cage VBR model is proposed to represent the induction machine deep bar effect. The advantage of the proposed model in simulation efficiency and accuracy is validated against with the induction machine short circuit transient simulation using larger time step, and the conclusion that the double cage induction machine model has better accuracy performance is verified.The main work of this thesis includes the study of squirrel cage induction machine literature, the derivation of the VBR model formula, and the realization of the VBR model on MATLAB-Simulink. The induction machine VBR model is expanded to the induction machine including saturation and deep bar effect, and the induction machine model including saturation using flux linkage as state variables and the double cage VBR induction machine model are proposed. The principle of the proposed VBR model is elaborated in detail, and the induction machine short circuit transient simulation is conducted on MATLAB-Simulink. The improvement of the proposed model on the numerical accuracy and computational efficiency is validated against with the comparison simulation. The major contribution of the above work is proposing a more advanced model for multiple machine short circuit calculation and fault simulation of wind farm, which decreases the simulation time and improves the model accuracy.