Performance Improvement of DFIG Wind Turbine Using Series Grid-Side Converter under Unbalanced Grid Voltage and Voltage Sag Conditions

Under unbalanced grid voltage conditions, the doubly fed induction generator (DFIG) stator voltage, in addition to positive sequence component has negative sequence component. The negative sequence component causes oscillations in the output power, electromagnetic torque and DC link voltage at twice the supply frequency. This paper presents a modified configuration of DFIG with series grid-side converter (SGSC) and its control system, which is suitable not only for unbalanced grid voltage conditions, but also for small voltage sags. The proposed configuration improves all the DFIG signals under unbalanced grid voltage and small voltage sag conditions without needing additional DC link capacitor or energy storage unlike other methods. The control system includes negative and positive sequence controllers which make the stator voltage balanced and keep it constant at the nominal value. Matlab/Simulink is used for simulation of a 1.5-MW DFIG and the results demonstrate the good efficiency of the proposed scheme. Keywords—doubly fed induction generator (DFIG);unbalanced voltage; voltage sag; series grid-side converter (SGSC)

[1]  Adel Nasiri,et al.  Digital control of three-phase series converter for DFIG wind turbine low voltage ride-through solution , 2011, 2011 Twenty-Sixth Annual IEEE Applied Power Electronics Conference and Exposition (APEC).

[2]  B. G. Fernandes,et al.  New direct torque control of DFIG under balanced and unbalanced grid voltage , 2010, TENCON 2010 - 2010 IEEE Region 10 Conference.

[3]  Kyo-Beum Lee,et al.  Performance improvement of a DFIG in a wind turbine under an unbalanced grid-voltage condition , 2010, 2010 IEEE International Symposium on Industrial Electronics.

[4]  G. Abad,et al.  Direct Power Control of Doubly-Fed-Induction-Generator-Based Wind Turbines Under Unbalanced Grid Voltage , 2010, IEEE Transactions on Power Electronics.

[5]  Lie Xu,et al.  Coordinated Control of DFIG and FSIG-Based Wind Farms Under Unbalanced Grid Conditions , 2010, IEEE Transactions on Power Delivery.

[6]  Eugene Coyle,et al.  The integrated control of the rotor side and grid side converters in a DFIG to reduce both power and torque pulsations during network voltage unbalance conditions , 2009, 2009 44th International Universities Power Engineering Conference (UPEC).

[7]  Barry W. Williams,et al.  Compensation of network voltage unbalance using doubly fed induction generator-based wind farms , 2009 .

[8]  J.A. Ferreira,et al.  Operation of Grid-Connected DFIG Under Unbalanced Grid Voltage Condition , 2009, IEEE Transactions on Energy Conversion.

[9]  Giri Venkataramanan,et al.  Unbalanced Voltage Sag Ride-Through of a Doubly Fed Induction Generator Wind Turbine With Series Grid-Side Converter , 2009, IEEE Transactions on Industry Applications.

[10]  Lie Xu,et al.  Control of DFIG-based wind farms for network unbalance compensation , 2008, 2008 IEEE Power Electronics Specialists Conference.