Primary frequency control by wind turbines

Transcription

1 Presented at 22 3rd IEEE PES ISGT Europe, Berlin, Germany, October 4 7, 22 Primary frequency control by wind turbines DiplIng Michael Wilch Prof DrIng István Erlich Institute of Electrical Power Systems University DuisburgEssen Germany Problem description Modern, convertercontrolled wind turbines do not provide inherent frequency response Replacement of synchronous generation by wind turbines lead to reduction of system inertia or 2

2 Presented at 22 3rd IEEE PES ISGT Europe, Berlin, Germany, October 4 7, 22 Grid Behavior Grid Loads Dependency Primary Control Secondary Control 5 Hz f min Seconds Minutes s 55 s 3 s 6 s Time 3 Contribution of WT to Grid Control Approaches: Standby Power by keeping Pitch Reserve Capacity Consequences and requirements: Less power generation Additional Grid Control Loop on Pitch Pitch drive has to meet dynamic frequency control requirements Utilizing Kinetic Energy of WT rotating mass Consequences and requirements: Discharge of energy to the grid is only for a short period available; after that accelerating power is taken from the grid Security limitations on rotor speed Additional Kinetic Energy Control Loop on electronic speed controller 4

3 Presented at 22 3rd IEEE PES ISGT Europe, Berlin, Germany, October 4 7, 22 Test Grid 7 MW Thermal ~ 5 km 3 MW Hydro primary controlled 6 MW Thermal 5 km ~ 38 kv km ~ L L2 WG DFIG Wind Farm 4 MW 4x25 km 33 kv Cables 35 MW Wind 2x 7 km, 5 kv Submarine Cable L PCC Load Switching 43+j5 MVA A dditional Load PCC 38 kv 5 Pitch Control and Wind Converter Model WT power p WT Rotor speed R ref Speed control thru Power V T st p max T WT ref power (to current controller) p WT_ref p TH Wind speed max std st V Pitch compensator max max v W st W R Turbine power and torque R_nom V st Speed control thru Pitch ref T A min s Pitch actuator min p m 3 ArotCP(, ) vw 2 Power conversion R t m 6

4 Presented at 22 3rd IEEE PES ISGT Europe, Berlin, Germany, October 4 7, 22 Speed Control Characteristic 7 Support by Pitch Control f Grid f Grid_ref +st K DP st VP K=f(P ) R R_ref : corresponds to P reserve capacity Only a Pcontroller is used in simulation 8

5 Presented at 22 3rd IEEE PES ISGT Europe, Berlin, Germany, October 4 7, 22 FSPC: Simulation Results mechanical turbine power in pu frequency in Hz FSPC without frequency support time in s 9 Kinetic Energy Control I p WT WT power p WT ref Speed control thru Power p max V T st T WT ref power (to current controller) p WT_ref Rotor speed R K +st D st V st W stw Grid Frequenc y p TH max std st V Pitch compensator During the KEC sequence gain V T is controlled KEC is limited to a specific R_min / R_max range max max Wind speed v W st W R Turbine power and torque R_nom V st Speed control thru Pitch ref T A min s Pitch actuator min p m 3 ArotCP(, ) vw 2 Power conversion R t m

6 Presented at 22 3rd IEEE PES ISGT Europe, Berlin, Germany, October 4 7, 22 KEC I: Simulation Results p in pu f in Hz 77 Supplied power by WT 5 76 Decelerating Energy 498 Grid WT drive power Accelerating Energy 72 drop recovery t in s New approach: Kinetic Energy Control II Grid without KEC II Phase 2 with KEC II Phase f min Phase 3 Time T s 5 5 s 3 s 6 s 2

7 Presented at 22 3rd IEEE PES ISGT Europe, Berlin, Germany, October 4 7, 22 Kinetic Energy Control II Speed control thru Power p additional p WT + power command Rotor speed R ref p max VT stt WT ref Power p WT_ref K +st D st V st st W Grid R_nom ma V st p TH Speed control thru Pitch Pitch std compensator stv st W Turbine R power and ma ma torque ref The only difference to KEC I: Plus sign instead of minus Different parameters T A mi s mi Pitch actuator Wind vw 3 AroCP(, ) vw 2 pm Power conversion R tm 3 KEC II: Simulation Results 8 p/pu Supplied power by WT Decelerating Energy WT drive power drop Accelerating Energy Grid 52 f/hz recovery drop t/s 49 4

8 Presented at 22 3rd IEEE PES ISGT Europe, Berlin, Germany, October 4 7, 22 Comparison of Results f in Hz No Control Control by Pitch KEC KEC t in s Conclusion Different options for wind turbines to support frequency possible: FSPC proves to be straightforward, actually increasing primary reserves KEC I: brake immediately at frequency drop, reaccelerate afterwards KEC II: gain speed during decrease, brake just before frequency minimum 6

9 Presented at 22 3rd IEEE PES ISGT Europe, Berlin, Germany, October 4 7, 22 Thank you for your attention! 7