1. Analysis of a 1.7 MVA Doubly Fed Wind-Power Induction Generator during Power Systems Disturbances Slavomir Seman, Sami Kanerva, Antero Arkkio Laboratory of Electromechanics Helsinki University of Technology Jouko Niiranen ABB Oy, Finland HELSINKI UNIVERSITY OF TECHNOLOGY Department of Electrical and Communications Engineering

2. Overview Introduction The Doubly Fed Induction Generator Frequency Converter and Control Crowbar Modeling of The Network, Transformer and Transmission Line Simulation Results Conclusions

3. The Doubly Fed Induction Generator P N 1.7 MW U N, stator (L-L) 690 V (delta) U max, rotor 2472 V (star) n N 1500 rpm f N, stator 50 Hz Transient Model of the Generator The machine equations x-y reference frame fixed with rotor Constant speed - no equation of movement included

4. Frequency Converter and Control Model of the Frequency Converter Two back-to-back connected voltage source inverters (VSI) DTC The Network Side Converter - simplification 1-st order filter transfer function PI controller U dc -level

5. The Rotor Side Converter Model of the Rotor Side Converter Modified DTC Input demanded PF or Q, T ref Voltage vector applied - optimal switching table The tangential component of the voltage vector controls the torque whereas the radial component increases or decreases the flux magnitude

6. Over-Current Protection - Crowbar Passive Crowbar over-current protection - the rotor, rotor side converter no chopper mode disconnection of the converter rotor is connected to CB CB is active until MCB disconnects stator from the network

7. Modeling of the Network, Transformer and Transmission Line Modelling of test set-up Power supply - SG or 3- phase V source with short circuit reactance and inductance Transmission line - R-L equivalent circuit Transformer - short circuit R-L and stray C, no saturation Short circuiting TR - R-L equivalent circuit

8. Simulation Results - Voltage Dip without Crowbar Matlab-Simulink, t_step = 0.5e-7, T_ref =0.5 p.u., w_ref = 1.067 p.u., Voltage dip 35% Un Voltage dip appliedMCB open

9. Simulation Results - Voltage Dip without Crowbar Voltage dip appliedMCB open

10. Simulation Results - Voltage Dip with Passive Crowbar Voltage dip appliedMCB open Matlab-Simulink, t_step = 0.5e-7, T_ref =0.5 p.u., w_ref = 1.067 p.u., Voltage dip 35% Un

11. Simulation Results - Voltage Dip with Passive Crowbar Voltage dip appliedMCB open

12. Transient behaviour of DTC controlled DFIG for wind-power applications studied. The transient simulation results with and without crowbar were compared. When the crowbar is implemented, the stator and rotor transient current decay rapidly and rotor circuit is properly protected. Transient electromagnetic torque is reduced by means of crowbar but oscillates longer than in case without crowbar. Conclusions