Planning And Operation Of Large Wind Farms In Areas With Limited Power Transfer Capacity

1. Planning And Operation Of Large Wind Farms In Areas With Limited Power Transfer Capacity by M. Korpås, J. O. Tande, K. Uhlen, E. S. Huse, T. Gjengedal magnus.korpas@sintef.no john.tande@sintef.no

2. Outline • Introduction: Wind integration in constrained grids • Case study specification • Description of simulation model • Smoothing of wind generation within a large area • Simulation results • Conclusions

3. Introduction • At many locations with excellent wind conditions the development of wind farms are hindered by grid issues. • The limit for wind power capacity is not easy to establish. • Conservative assumptions are often applied that unnecessarily limits the wind power installation. • This presentation shows that significantly more wind power can be allowed by: • taking account for the wind power characteristics • facilitating coordinated power system operation. • The combination of wind and hydro (with storage) is of particular interest, and used as a case for this presentation.

4. Case study specifications Automatic Generation Control or manual by System Operator Wind farms (115 MW - ??) AGC Load (MW) 1940 GWh/y Local loads Hydro power plants 380 MW w 760 GWh reservoir 132 kV corridor Max transfer capacity 420 MW Hydro inflow (MWh/h) 420 kV main transmission 2110 GWh/y

5. Simulation model • Simulate 30 years operation on an hour-by-hour basis • Model inputs include: • 30-year time series with inflow to hydro reservoir and wind power • Statistical variations in consumer load and electricity price from the EMPS-model (Multi-area Power-market Simulator). • Specification of the power system components, including: • hydro storage capacity • rated power of hydropower plant • thermal limits of 132 kV transmission lines • Assumed AGC strategy: • The AGC operates to avoid line overloading • Controlhydro: control the hydropower first and secondary the wind power (if needed) • Control wind: control the wind power only

6. Long-term wind and inflow variations

7. Hour by hour wind power variations

8. Hour by hour wind power variations

9. Simulation of 3x200 MW wind farms • Control wind

10. Simulation of 3x200 MW wind farms • Control hydro

11. Simulation of 3x200 MW wind farms summation of three wind farms simple scaling of wind production congested wind hydro

12. Income vs. wind capacity control hydro Year with lowest income reduction Year with highest income reduction control wind

13. Summary results from case study • Simplified and conservative assumptions allow less than 200 MW of wind power • Significantly more is possible by: • assuming coordinated control • taking account for the geographical wind smoothing effect • Installation of 600 MW of wind power results in: • no significant reduction in income from energy sales if adjusting hydro generation • only 1-5 % reduction of income if constraining wind power and leaving hydro according to schedule (all compared to the non-congested case)

14. Conclusion • Power system coordination allows for surprisingly large amounts of wind power. • It is essential to take account for the power system flexibility and the stochastic and dispersed nature of wind power. • The presented methodology facilitates this and represents a rational approach for power system integration of wind farms in areas with limited transfer capacity.