Research challenges for offshore HVDC grids and its components Torbjörn Thiringer Dep. of Energy and Environment Chalmers University of technology Göteborg, Sweden NTNU, SINTEF, Trondheim Chalmers, Göteborg HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 1(30)
Why offshore HVDC grid ( in the North Sea )? Economical benefit to make power transfer and to balance power variations in different parts of Europe with the Baltic and North Sea in-between To long distances for AC ( could perhaps work with 15 Hz AC ) HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 2(30)
Why offshore HVDC grid with wind turbines? Interest for installing wind energy in Sea areas space and wind speed issues 20-20-20 Kyoto protocol Peak Oil HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 3(30)
SW corner of North Sea HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 4(30)
The supergrid HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 5(30)
HVDC system with offshore wind farm HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 6(30)
Research challenges System: overall operation stability - connection to external ac-grids - cable and grid component dimensioning - grid code insulation level protection current interuption meshed vs nonmeshed sequential building strategy dc switchgear station DC-transformer design operation extra functionality WEC system high efficiency robust direct drive? converter-voltage levels- HVDC out HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 7(30)
Some thoughts/ideas/aspects HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 8(30)
Step-wise building HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 9(30)
Converter topologies 2-level n-level 3-level HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 10(30)
Series connected dc wind farm I stack,1 I stack,2 I stack,m WT 1,1 + V WT,1,1 - WT 1,2 + V WT,1,2 - WT 1,m + V WT,1,m - WT 2,1 + V WT,2,1 - WT 2,2 + V WT,2,2 - WT 2,m + V WT,2,m - + I dc dc ac PCC WT n,1 + V WT,n,1 - WT n,2 + V WT,n,2 - WT n,m + V dc V WT,n,m - - HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 11(30)
No 50 Hz transformers HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 12(30)
Grid Code Line-to-line U voltage U N Required additional reactive current I I N B reactive current rated current -50% Fault occured Time in ms m=2-100% Voltage drop U U N HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 13(30)
DC breaking HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 14(30)
DC breaker current HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 15(30)
Some research examples HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 16(30)
Example of system study Geographical locations For hourly average wind speed data in the North Sea region Vector ARIMA(6,0,0) HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 17(30)
Existing HVDC transmission Real exchange power Exchange Power [MW] 1000 500 0-500 NL=>NO -1000 0 20 40 60 80 100 Duration [%] System dimensions HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 18(30)
Adding a wind farm of 1700 MW WF 1 capacity=1700 MW Branch power Uncontrolled Branch Power [pu] Uncontrolled Branch Power [pu] 3 2 1 0-1 -2 NO->WF 1 NL->WF 1-3 0 10 20 30 40 50 Time [hour] 3 2 1 0-1 -2 NO->WF 1 NL->WF 1 (84%,1) -3 0 20 40 60 80 100 Duration [%] Over loaded for about 15% of the year HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 19(30)
Multiterminal with added wind farms [WF1 WF2] capacity=[1700 2700] MW Exchange power Uncontrolled Branch Power [pu] 3 2 1 0-1 -2-3 NO->WF 1 NL->WF 1 DE->WF 2 DK->WF 2 WF 1->WF 2-4 0 20 40 60 80 100 Duration [%] Peak >3pu >30% 1117MW HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 20(30)
Multiterminal with added wind farms Controlled Branch Power [pu] 3 2 1 0-1 -2 NO->WF 1 NL->WF 1 DE->WF 2 DK->WF 2 WF 1->WF 2-3 0 20 40 60 80 100 Duration [%] HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 21(30)
Added cost and reinforcement Reinforcing the system Added cost [M ] Added cost [M ] 400 300 200 100 0-100 0 0.34 0.68 1.02 1.36 1.7 WPP capacity [GW] 300 200 100 0 Base case Reinforce-NO->WF1 Reinforce-NL->WF1 Base case Reinforce with 216MW Reinforce with 317MW Reinforce with 490MW NPV of system added cost [M ] 600 400 200 0-200 -400 Ttariff=10 /MWh Ttariff=13 /MWh Ttariff=18 /MWh -600 0 0.34 0.68 1.02 1.36 1.7 WPP capacity [GW] -100 0 0.34 0.68 1.02 1.36 1.7 WPP capacity [GW] HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 22(30)
Collection grid of offshore wind farm Typical offshore HVAC collection grid Existing VSC-HVDC collection grid AC Cables Bulky 50 Hz transformers Bulky 50 Hz transformers Future HVDC collection grid High power density converters using HF High Power transformers DC medium voltage cables HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 23(30)
The dc-transformer Future HVDC collection grid with HF / MF transformers : Modular structure (PISO) : HF high power transformer + inductor One module with HFT : HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 24(30)
Design and Optimization (Case Study) Optimization results 600 000 combinations of free parameters HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 25(30)
HF Resistance measurement HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 26(30)
DC-link voltage selection HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 27(30)
DC-link voltage and losses HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 28(30)
Other generators - SynRG 74 % of power given the same volyme HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 29(30)
Questions? HVDC grids & its components - Torbjörn Thiringer, CTH - EERA Deep wind 2015 30(30)