1. 1 GENERATORS AND CONVERTERS IN LOW AND MEDIUM VOLTAGE WIND ENERGY CONVERSION SYSTEMS Dr. Josep Bordonau (Technical University of Catalonia, Barcelona, Spain) Iñigo Garin (IKERLAN, Arrasate, Spain) Dr. Salvador Alepuz (EUPMT-UPC, Mataró, Spain)

2. 2 Outline Introduction Wind Generation Systems Technologies Generators Power Electronics Converters Future trends Conclusions

3. 3 Introduction Wind Generation Systems Technologies Generators Power Electronics Converters Future trends Conclusions

4. 4 Introduction Total wind power installed in the world (MW) Average size of installed wind generators (kW) Comparison of the current trend with the White Paper objectives (MW)

5. 5 Introduction Wind Generation Systems Technologies Generators Power Electronics Converters Future trends Conclusions

6. 6 Generators Constant Speed Systems Squirrel Cage Asynchronous Generator Cheap & Simple Torque variations not compensated Flicker Capacitors to compensate reactive power

7. 7 Variable Speed Systems Squirrel Cage Asynchronous Generator Optimum power control 100% speed variability Converter size Expensive Generators

8. 8 Variable Speed Systems Optimum power control 100% speed variability Without Gearbox Converter size Generator complexity Very expensive Permanent Magnet Synchronous Generator Generators

9. 9 Variable Speed Systems Doubly Fed Wounded Rotor Asynchronous Generator Optimum power control Converter size Restricted speed variability Expensive Generators

10. 10 Introduction Wind Generation Systems Technologies Generators Power Electronics Converters Future trends Conclusions

11. 11 Converters Traditionally: Two level structure + transformer (New) High Power Semiconductors New Topologies Mature technology in wind industry High availability Grid decoupling Commutation losses Filters Intrinsic LV operation

12. 12 Tandem Converter Resonant Converter Matrix Converter Higher efficiency Better dynamic properties Cost & Complexity Filter Oversized Without Passive components Less filter requirements No availability of bidirectional switches Coupling grid and generator Complex protection Need for auxiliary circuits Ride-through Less commutation losses Complex Hardware & Control High energy flux in resonant circuit Converters

13. 13 Multilevel Converters Cascaded H bridges Need for isolated DC-links Flying capacitors, Multicell Reduced availability Diode clamped, DCM, NPC High voltage capacity Reduced commutation losses Small harmonic content Reduced filters, faster response Reduced common-mode voltage Capacitor voltage balancing Conduction losses More components Converters

14. 14 Introduction Wind Generation Systems Technologies Generators Power Electronics Converters Future trends Conclusions

15. 15 Future trends Progress in Power Electronics: –High Voltage devices –New materials (SiC): reduced losses and faster response –New converters: multilevel converters Practical results with multilevel technology: –MV feasible w/o step-up transformer –Benefits in Cupper losses –Benefits in Cupper reduction –Benefits in filter size –Benfits in common-mode voltage reduction (good for the bearings) –Benefits in faster response –Slight overcost compared with conventional 2-level converters (about 10 %)

16. 16 Introduction Wind Generation Systems Technologies Generators Power Electronics Converters Future trends Conclusions

17. 17 Conclusions

18. 18 Conclusions

19. 19 Practical results with multilevel technology: –MV feasible w/o step-up transformer –Benefits in efficiency (Cupper loss reduction) –Benefits in electrical cost (Cupper reduction) –Benefits in filter size –Benfits in common-mode voltage reduction (good for the bearings) –Benefits in faster response (grid connection) –Slight overcost compared with conventional 2-level converters (about 10 %)

20. 20 Thank you for your Attention Introduction Wind Generation Systems Technologies Generators Power Electronics Converters Future trends Conclusions Introduction Wind Generation Systems Technologies Generators Power Electronics Converters Future trends Conclusions