Introduction CONTENT Future of offshore wind energy in Europe Offshore wind energy in Spain Alternatives to the transmission system to the grid Compar

Transcription

1 OFFSHORE WIND FARM CONNECTIONS TO THE GRID Energy to Quality S.L. Santiago Arnaltes Gómez

2 Introduction CONTENT Future of offshore wind energy in Europe Offshore wind energy in Spain Alternatives to the transmission system to the grid Comparison between different technologies to transmit the energy to the shore. Conclusions

3 INTRODUCTION Offshore wind farms (vs on shore) More powerful wind turbines Higher foundation costs 30% of total project cost vs 5% Length increase of electric connections inside the farm and to the grid Different grid connection systems (AC or DC) New problems to fulfill network requirements Overall cost increase of wind farm electric system

4 FUTURE OF OFFSHORE WIND ENERGY IN EUROPE Objectives in Europe - offshore wind power: Germany: 25 GW offshore wind power in 2030 United Kingdom: 33 GW forecasted, in different development phases Sweden: 2,5 3 GW, increasing it by a factor of 25 in 2020 Denmark: Leader in offshore wind power Investment in transmission system and grid connection Financial limitations delay in offshore developments

5 FUTURE OF OFFSHORE WIND ENERGY IN EUROPE Copenhagen Strategy 2005, from EWEA Development of the sector, R+D with private and public funding Creation of grid access infrastructures Elaboration and coordination of environmental studies

6 OFFSHORE WIND ENERGY IN SPAIN High wind energy resources available in the Spanish coastline. Objective: 4 GW in Administration: Administrative authorizations. Environmental impact. 43% of the coastline allows offshore installations. Present: pre-applications for over 30 installations adding up more than 7 GW.

7 ALTERNATIVES TO TRANSMISSION SYSTEM Electric transmission system - 30 % of total project budget. Design criteria: Compact and maintenance free Redundance in critical points Corrosion resistance Existing offshore wind farms: km from the coast and <160 MW - HVAC transmission From km and more powerful wind farms - HVDC transmission

8 High Voltage Alternate Current (HVAC) Lower investment and greater experience that HVDC Low to medium distances to the coast and farm installed power Q in cables necessary to install external compensation systems (STATCOM or SVC).

9 High Voltage Direct Current transmission system (HVDC) LCC based High distances to the coast and high power. No reactive power production. Possibility of variable frequency inside the wind farm High initial budgets and lack of experience

10 High Voltage Direct Current transmission system (HVDC) LCC based Q compensation at both AC sides converter consumption Harmonic filters required Space needed for offshore and onshore converting stations AC-DC DC-AC conversion efficiency around %

11 High Voltage Direct Current transmission system (HVDC) VSC based Better stability. Q control at each side of the net Independent control of active and reactive power. No external compensation systems Better harmonic distortion - no filters needed.

12 High Voltage Direct Current transmission system (HVDC) VSC based High initial budgets and no experience Limitation in power transmission (< 400 MW) High conversion frequency - losses AC-DC DC-AC conversion efficiency around 94 %

13 Transmission capacity TECHNOLOGIES COMPARISON SYSTEM AC WIRE DC WIRE ISOLATION XLPE OIL OIL IMPREGNATED PAPER XLPE MAX VOLTAGE 400 kv 500 kv 600 kv 500 kv 150 kv MAX POWER 1200 MVA 1500 MVA 2400 MW 2000 MW 500 MW MAX LENGTH (km) No limit No limit

14 Load losses TECHNOLOGIES COMPARISON

15 TECHNOLOGIES COMPARISON Marine stations size HVAC systems < HVDC systems Connection to external land grid HVAC and HVDC-LCC are not indicated to connect to weak grids Control of active and reactive power, voltage level, etc: better with HVDC-VSCVSC

16 Installations costs TECHNOLOGIES COMPARISON POWER LENGTH BETTER SOLUTION UNTIL 200 MW l<100 km 250<l>100 km HVAC (Vmax= 170kV) HVDC-VSC HVDC-LCC l>250 km HVDC-VSC MW l<100 km HVDC l>100 km HVDC-VSC MW Not determinant HVDC-LCC MW Not determinant HVDC-LCC HVDC-VSC > 900 MW Not determinant HVDC-LCC

17 CONCLUSSIONS Specific problems from offshore connection to the grid Transmission systems sizing Reactive power compensation systems and filters The need to have specific Grid Codes and verify procedures Importance of experience and low cost in AC systems Voltage and power control capacity in HVDC systems

18 ABOUT E2Q Electrical services company and test laboratory Experience in both direct testing and generator and wind farms model validation Portable voltage dips generator

19 ABOUT E2Q LVRT test - experience in main international grid codes Power quality Grid integration studies Accredited to ISO Member of MEASNET

20 Thanks for your attention Energy to Quality S.L. Pº Castellana 114, Madrid - Spain Mail: amolina@energytoquality.com