Presented at rd IEEE PES ISGT Europe, Berlin, Germany, October 14-17, 2012

Transcription

1 Presented at rd IEEE PES ISGT Europe, Berlin, Germany, October 14-17, 2012 Power-electronic asset characteristic for converter-dominated offshore grids Dr.-Ing. Carsten Heising, Dipl.-Ing. Daniel Meyer and Dipl.-Ing. R. Bartelt (Avasition GmbH) Dr.-Ing. M. Koochack Zadeh, Dr.-Ing. T.J. Lebioda and Dr.-Ing. J. Jung (TenneT Offshore) Content General aspects Objectives and expectations Typical configurations and characteristics of offshore grids Stability-aspect overview and demonstrative example Motivation Example: Proposed asset characteristic for dynamic power balancing especially for future extension stage of the offshore grids e.g. parallel connection of two or more HVDC links and for certain operating scenarios e.g. overload scenario Conclusion 2

2 Presented at rd IEEE PES ISGT Europe, Berlin, Germany, October 14-17, 2012 Content General aspects Objectives and expectations Typical configurations and characteristics of offshore grids Stability-aspect overview and demonstrative example Motivation Example: Proposed asset characteristic for dynamic power balancing especially for future extension stage of the offshore grids e.g. parallel connection of two or more HVDC links and for certain operating scenarios e.g. overload scenario Conclusion 3 Objectives and expectations Expected installed capacity offshore ,000 MW (dena II) 10,000 MW (German Federal Government ) ,000 MW At the moment 140 MW Currently approved OWF North Sea 24 in EEZ* plus 2 in territorial waters 7,800 MW in EEZ Currently planned OWF North Sea Over 50 in EEZ (for approval by BSH) source: BSH *) EEZ Exclusive Economic Zone 4

3 Presented at rd IEEE PES ISGT Europe, Berlin, Germany, October 14-17, 2012 Offshore grid connections north sea SylWin1 (alpha) BorWin2 (beta) BorWin1 (alpha) Riffgat HelWin2 (beta) HelWin1 (alpha) alpha ventus DolWin1 (alpha) DolWin2 (beta) DolWin3 (gamma) Nordergründe UW Hagermarsch UW Büttel UW Emden Borssum UW Inhausen UW Diele UW Dörpen West State: 09/2011 (alpha), (beta), (gamma): platform names 5 Project interfaces AC und DC concepts OWP OWP see platform OWP Tennet Offshore OWP (n) OWP see platform OWP Tennet Offshore HVAC cable offshore HVDC converter HVDC cable Tennet TSO onshore HVDC converter Tennet Offshore Tennet TSO 6

4 Presented at rd IEEE PES ISGT Europe, Berlin, Germany, October 14-17, 2012 Typical structure of OWF and their connection systems Offshore Wind Farms Characteristics HVDC Connection Systems (single or parallel connection) Sea Cable Land Cable Converter Offshore, Filter, Compensation, etc. Converter Onshore, Filter, Compensation, etc. Cable grid with various number of power-electronic devices Interaction of power-electronic devices not neglectable due to very limited short-circuit power Rated power of HVDC in the same range of the rated power of connected OWF Onshore Netw ork Infinite possible configurations 7 Challenges in Offshore Grid OWF short-circuit power low, converter control affects local grid voltage considerably Stability assessment: additional requirements especially for future extension stage of the offshore grids e.g. parallel connection of two or more HVDC links and for certain operating scenarios e.g. overload scenario 8

5 Presented at rd IEEE PES ISGT Europe, Berlin, Germany, October 14-17, 2012 Stability-aspect overview Comprehensive and transferable experiences in other applications (e.g. Railway) High-frequency stability (not accessible by control) Critical aspects: interaction of filters and cables design issue Cable grids: Weak damping / resonant points frequency domain simulation is reasonable Medium-frequency stability (result of control and control interaction) Critical aspects: interaction of control, filters and cables Time domain vs. frequency domain Low-frequency stability (result of control and control interaction) Critical aspects: interaction of control Occur in case of multiple converters in weak grids and converter grids Time domain simulation necessary and reasonable 9 Demonstrative example: low-frequency stability Simulation properties Test cases with generic wind park and generic converter control simulated Interval-based simulation used (software environment Avasition VIAvento ) Results 24 wind-energy plants with dq control unstable 24 wind-energy plants with pole-restraining control stable Lessons learned High impact of converter control on low-frequency stability 10

6 Presented at rd IEEE PES ISGT Europe, Berlin, Germany, October 14-17, Wind-energy plants dq controlled 5 u dc i AC,WKA Wind-energy plants PR controlled 5 u dc i AC,WKA High impact of converter control on low-frequency stability 12

7 Presented at rd IEEE PES ISGT Europe, Berlin, Germany, October 14-17, 2012 Content General aspects Objectives and expectations Typical configurations and characteristics of offshore grids Stability-aspect overview and demonstrative example Motivation Example: Proposed asset characteristic for dynamic power balancing especially for future extension stage of the offshore grids e.g. parallel connection of two or more HVDC links and for certain operating scenarios e.g. overload scenario Conclusion 13 Proposal for dynamic power balancing in converter dominated offshore grids Major differences between conventional and power-electronic (PE) assets. No coherence between frequency and power Additional requirement: no master-slave approach (Essential for high availability in complex multi-terminal configurations) Proposed solution (based on absolute time signal) Operating grid frequency is defined as constant Grid angle is used for grid-state communication P Consequence Much faster grid-state communication Allows for overshot prevention in overload situations 14

8 Presented at rd IEEE PES ISGT Europe, Berlin, Germany, October 14-17, 2012 Simulation of overload scenario (overview) Consumer (HVDC) Consumer (HVDC) Supplier (wind farms) Supplier (wind farms) Reference point t[s] Action Description 0.02 Enableconverter14 Acceleratingtobalancedoperation 0.5 Enable converter 5 Overload HVDC 1.0 Disable converter 4 and 5 Overload wind farm(load rejection) 1.5 Enable converter 4 Balanced operation 15 Simulation of overload scenario (zoom) Consumer (HVDC) Supplier (wind farms) Consumer (HVDC) Reference point Supplier (wind farms) P 16

9 Presented at rd IEEE PES ISGT Europe, Berlin, Germany, October 14-17, 2012 Content General aspects Objectives and expectations Typical configurations and characteristics of offshore grids Stability-aspect overview and demonstrative example Motivation Example: Proposed asset characteristic for dynamic power balancing especially for future extension stage of the offshore grids e.g. parallel connection of two or more HVDC links and for certain operating scenarios e.g. overload scenario Conclusion 17 Conclusion Characteristics of the offshore grids as converter dominated grids converter control interaction: low-frequency stability Proposed asset characteristic for dynamic power balancing especially for future extension stage of the offshore grids e.g. parallel connection of two or more HVDC links and for certain operating scenarios e.g. overload scenario 18

10 Presented at rd IEEE PES ISGT Europe, Berlin, Germany, October 14-17, 2012 Thank you for your attention! 19