Introduction: Offshore wind energy will become an important energy source in the near future. On the other hand, the low efficiency of gas turbines or diesel engines at offshore oil & gas installations calls for alternative power supplies. Therefore it is necessary and possible to integrate oil installations and offshore wind farms to the onshore grid by single transmission link. This poster presents an analysis and fault mitigation methods of grid integration of offshore wind farms and oil & gas installations using Voltage Source Converter (VSC) HVDC. VSC HVDC offshore transmission Offshore AC Frequency Control The fixed frequency control strategy is used. First, it enable the VSC to absorb the fast changing wind power generation and achieve bi-direction power transmission. Second, the extra power control loop is not needed, therefore, fast offshore communication systems are not necessary. Grid Integration of Large Offshore Wind Energy and Oil& Gas Installations Using VSC-HVDC Bing Liu, Department of Electric Power Engineering, NTNU [email protected] Acknowledgements: This research was presented under assistance of Statkraft Ocean Energy Research Program. References : [1] Bing Liu; Jia Xu; Torres-Olguin, R.E.; Undeland, T.; “ Faults mitigation control design for grid integration of offshore wind farms and oil & gas installations using VSC HVDC”, SPEEDAM, PP. 792 – 797, June 2010 Vvsc PI VAC* e M f* 2π s jθ PLL Voltage depen- dent limiter vq* 0 VAC Onshore grid fault: DC link over voltage and offshore AC voltage variation during onshore fault. DC link voltage control (DLVC): An offshore AC grid voltage independent limiter is implemented in the ac voltage control loop via the modulation index (M) of the VSC: Proposed DC Link Voltage Controller With DLVC controller presence, the HVDC DC voltage, offshore AC voltage and offshore AC frequency (green solid curves in upper figure a and b) peak values are smaller than the configuration without DLVC controller. Offshore AC Grid Fault Mitigation: The exact design of the Vac versus Vvsc curve in below figure is depends on the detailed VSC design and how fast the wind generation recovers from faults, in order to reach the active power balance in the offshore AC grid. Vac vs Vvsc relationship in voltage dependent limiter. Conclusions: Several faults mitigation control strategies for the offshore VSC HVDC grid integrating offshore wind farm and oil & gas installations has been proposed in this project stage, for example, the DC link voltage controller for onshore grid faults and the voltage dependent limiter for offshore AC grid faults. Simulation results in PSCAD show the satisfied performance. Currents of wind farm, offshore VSC and oil platform (with ac voltage limitation 1.5 p.u. at offshore VSC) Currents of wind farm, offshore VSC and oil platform (with ac voltage limitation 1.1 p.u. at offshore VSC)
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Introduction:Offshore wind energy will become an important energy source in the near future. On the other hand, the low efficiency of gas turbines or diesel engines at offshore oil & gas installations calls for alternative power supplies. Therefore it is necessary and possible to integrate oil installations and offshore wind farms to the onshore grid by single transmission link. This poster presents an analysis and fault mitigation methods of grid integration of offshore wind farms and oil & gas installations using Voltage Source Converter (VSC) HVDC.
VSC HVDC offshore transmission
Offshore AC Frequency Control
The fixed frequency control strategy is used. First, it enable the VSC to absorb the fast changing wind power generation and achieve bi-direction power transmission. Second, the extra power control loop is not needed, therefore, fast offshore communication systems are not necessary.
Grid Integration of Large Offshore Wind Energy and Oil& Gas Installations Using VSC-HVDC
Bing Liu, Department of Electric Power Engineering, [email protected]
Acknowledgements:This research was presented under assistance of StatkraftOcean Energy Research Program.
References :[1] Bing Liu; Jia Xu; Torres-Olguin, R.E.; Undeland, T.; “ Faults mitigation control design for grid integration of offshore wind farms and oil & gas installations using VSC HVDC”, SPEEDAM, PP. 792 – 797, June 2010
Vvsc
PIVAC*
e
M
f* 2πs
jθ
PLL
Voltage depen-dent limiter
vq*0VAC
Onshore grid fault:
DC link over voltage and offshore AC voltage variation during onshore fault.
DC link voltage control (DLVC):An offshore AC grid voltage independent limiter is implemented in the ac voltage control loop via the modulation index (M) of the VSC:
Proposed DC Link Voltage Controller
With DLVC controller presence, the HVDC DC voltage, offshore AC voltage and offshore AC frequency (green solid curves in upper figure a and b) peak values are smaller than the configuration without DLVC controller.
Offshore AC Grid Fault Mitigation:
The exact design of the Vac versus Vvsccurve in below figure is depends on the detailed VSC design and how fast the wind generation recovers from faults, in order to reach the active power balance in the offshore AC grid.
Vac vs Vvsc relationship in voltage dependent limiter.
Conclusions:Several faults mitigation control strategies for the offshore VSC HVDC grid integrating offshore wind farm and oil & gas installations has been proposed in this project stage, for example, the DC link voltage controller for onshore grid faults and the voltage dependent limiter for offshore AC grid faults. Simulation results in PSCAD show the satisfied performance.
Currents of wind farm, offshore VSC and oil platform (with ac voltage limitation 1.5 p.u. at offshore VSC)
Currents of wind farm, offshore VSC and oil platform (with ac voltage limitation 1.1 p.u. at offshore VSC)
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