Grid Code Testing of Wind Turbines by VSC-based Test Equipment

Transcription

1 Grid Code Testing of Wind Turbines by VSC-based Test Equipment Nicolás Espinoza, PhD Student CHALMERS VÄRLDENS UNIVERSITY SKILLNAD OF TECHNOLOGY Gothenburg, Sweden. 1 of 32

2 Project Description Aim of the project To develop methods for grid code testing of wind turbines using VSC-based test system. Activities Grid code analysis for interconnection of wind parks. Control theory of WT and VSC. Mathematical model for stability analysis. Results Simulation of the WT and the VSC-based test equipment (TE). Laboratory experiment at Power System Lab in Chalmers. Field test of full power 4 MW WT with 8 MW HV system in Göteborg harbor has started! 2 of 15

3 Wind Power Increase World total installed capacity is 318 GW (117 GW are inside EU) 40 GW per year in the last 5 years, approximately. GW installed Year 3 of 15

4 Grid code development Regulates the interconnection of the generating plant. Special requirements for wind parks. Steady state: voltage, power and frequency ranges. Dynamic: LVRT and reactive current injection (if allowed). Grid code harmonization: ENSTO, Nordic. 4 of 15

5 Low Voltage Ride Through (LVRT) Voltage dip representation at the connection point System Voltage [pu] E.ON (Germany) National Grid (U.K.) Red Eléctrica España (Spain) EirGrid (Ireland) Energnet.dk (Denmark) Svenska Kraftnät (Sweden) Nordel Time [s] 5 of 15

6 Wind Turbine Topologies Full-size converter WT Grid synchronization Current during fault is fully controlled. LVRT control. Wind turbine Gearbox/ Gearless Generator G Full Power Converter Protection by crowbar Control system Coupling inductor and filters Output transfomer Grid DFIG WT Stator connected to the grid. High transient current during fault. VSC rated in 1/3 P nominal. Poor LVRT capability. Wind turbine Gearbox DFIG 1/3 Power Converter Coupling inductor and filters Protection by crowbar Output transfomer Grid Protection by crowbar Control system 6 of 15

7 Wind Turbine Modelling Assumptions Physical decoupling between Generator and grid. Mechanical transients are slow compare to electromagnetic transients. Wind turbine Gearbox/ Gearless Generator G Full Power Converter Protection by crowbar Control system Coupling inductor and filters Output transfomer Grid si P GEN i, w C w, u w, WT-VSC uw i t, w R f, w L f, w e w C f, w TW To Test equipment e wg, i w, g sw crb R crb 7 of 15

8 Grid Code Testing Equipment Impedance-based Impedance-based Test equipment Z series Grid impendace VSC-based Z fault Test Equipment: VSC in back-to-back Coupling transfomer PCC Interface impedance voltage control for LVRT voltage control Interface impedance Coupling trasnformer Grid 8 of 15

9 Stability Analysis Analytical model based on physical equations and control equations. Study of interactions between WT and Test Equipment WT-VSC Interface impedance PCC Collector-VSC i, w u, w uw i t, w e w i g e i t u i s C, w R f, w L f, w C f, w R eq Leq Cf L f R f Well damped area CL vs OL voltage CTRL Blue: P-based controller Red: PI-based controller Black: Open-loop 9 of 15

10 Laboratory Setup Placed at the Power System Lab. at Chalmers University of Technology. Consisting of 2 -sourced VSC interfaced by an -link. 200 V, 10 kva. grid, 400 V, 50 Hz R l Wind Turbine Model C, w u w, u t, w i t, w P, Q wt wt L f R,, 2 f,2 -link C f e L f R,, 1 f,1 i t Grid Emulator u u machine 360 V C voltage control for LVRT R crb DS1103 DS of 15

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13 Field Test Results 13 of 15

14 Flexible VSC-based Testing Equipment Turbine VSC Grid VSC Utility Grid 14 of 15

15 Conclusions and Future Work Conclusions Need for regulations for renewable energy sources. VSC-based T.E. is flexible Development of PCC voltage control and control algorithms. Future Work To develop control strategies for testing of: Voltage control Power oscillation damping Frequency control Characterization of wind turbines To include wind turbine mechanical system 15 of 15

16 Thanks for your attention Nicolás Espinoza, PhD Student CHALMERS UNIVERSITY OF TECHNOLOGY Gothenburg, Sweden. 16 of 15