4th Meeting,, 26-27 April 2007 Comparative Study of Forecasts Eng. Ana RosaTrancoso (IST) Eng. Rui Pestana (REN) Prof. José Delgado Domingos (IST) ana.rosa.maretec@ist.utl.pt Goal Eolic Power Forecast for TSO (Transmission System Operator) Load scheduling strategy (daily basis) Dispatching decisions (hourly basis) Motivation MM5 runs 4 times per day (00,06,12,18) with 72h forecasts, 23 vertical levels and GFS 80km. Best prediction? WRF 80km? WFR 40km? 2
Transmission System Operator (TSO) Wind Speed Forecast 3 IST-MM5 http://meteo.ist.utl.pt Operacional desde 2000. Online desde 2001. 82x55 dx = 9 km 40x50 dx = 81 km 55x40 dx = 27 km 4
REN Power Forecast Persistence: 13 online parks (700 MW) Improves short time scales Correct NWP initial forecast Outages: Wind farm outages REN lines outages EDP-Distribuição lines outages http://www.ren.pt/sections/exploracao/dpe/default.asp 5 Forecasts with MM5 ID MM5_00 MM5_12 REN Reg Coef Coef.Reg Description MM5 D3 (9km) with GFS 80km, start at 00Z. MM5 D3 (9km) with GFS 80km, start at 12Z (uses upper air soundings data in Portugal) Combination of MM5 most recent forecasts. Stepwise regression with the 11 available forecasts for each hour. Weigthed regression of REN forecast with observed data, every 6 hours Weigthed regression of Coef forecast with observed data, every 6 hours 6
Stepwise Regression 1:00 6:00 7:00 12:00 18d1 18d2 00d0 1.0 0.5 0.0 00d1 00d2 ACD ADI AGM AHF 18d1 18d2 00d0 1.0 0.5 0.0 00d1 00d2-0.5 AIL AIT -0.5 18d0-1.0 06d0 18d0 AIV -1.0 06d0 12d2 18d1 12d1 18d2 0.5 0.0-0.5 12H 06d2 Nov Dez 2006 12d0 00d0 1.0 00d1 06d1 00d2 ANM APO APZ 12d2 ATD 13:00 18:00 19:00 0:00 ATE AZM ACD ADI AGM AHF 18d1 AIL AIT 12d1 18d2 0.5 0.0-0.5 18H 06d2 Nov Dez 2006 12d0 00d0 1.0 00d1 06d1 00d2 ACD ADI AGM AHF AIL AIT AIV ANM APO APZ ATD ATE AZM 18d0-1.0 06d0 18d0 AIV ANM -1.0 06d0 APO 12d2 06d1 APZ 12d2 ATD 06d1 12d1 12d0 06d2 ATE AZM 12d1 12d0 06d2 7 Stepwise Regression 1 NovDez 2006 R 2 of Regressions R^2 0.9 0.8 0.7 0.6 0.5 0.4 0.3 00H 06H 12H 18H Reg from 13:00-18:00 is the one with higher correlation 0.2 0.1 0 AIV AZM ATE APZ AIL ATD ACD AIT AHF ADI ANM AGM APO Parque Park Positive Coefficients Frequency Contributions of each forecast in the regressions 16% 14% 12% 10% 8% 6% 4% 2% d0 d1 d2 0% s00 s06 s12 s18 8
Cumulative Square Error Jan, Fev, Mar 2007 for 13 parks MM5_00 MM5_12 REN Reg Coef.Reg time Coef Increase in wind velocity! 9 Increase 24-Jan-2007 25-Jan-2007 26-Jan-2007 10
Decrease 12-Jan-2007 14-Jan-2007 GOOD forecast BAD persistence BAD forecast GOOD persistence 11 Antecipated Increase 21-Jan-2007 22-Jan-2007 Predicted at 18h... Ocurred at 03h 12
Error Decomposition 2 2 2 2 2 rmse = bias + sde = bias + sdbias + disp 2 ε = rmse = bias = ε x prd x obs 2 ε sde = σ (ε ) sdbias = σ ( x prd ) σ ( xobs ) Error Root Mean Square Error Bias Standard Deviation of Error Variability Error disp = 2σ ( x ) σ ( x )(1 r) prd obs Dispersion (phase error) Lange M. (2005). On the Uncertainty of Wind Power Predictions Analysis of the Forecast Accuracy and Statistical Distribution of Errors. Journal of Solar Energy Engineering. Vol. 127:177-184. 13 Error Decomposition RMSE MAE RMSE BIAS SDE SDBIAS DISP Bias > 0 : underestimation RMSE ~ SDE ~ DISP : Phase Errors Hours RMSE of coef prediction increases steeply. Try to reduce with regression Decrease in RMSE near end of day (18h) higher winds 14
Improvement Relative to coef Relative to reg Relative to REN Coef is the best prediction Coef.reg improves sligtly (except for 13-18h) NWP forecasts better than reg at daynight transitions MM5_12 best than REN at 1-6h (which is MM5_18) MM5_00 best than REN at 13-18h (which is MM5_06) REN could be combination of MM5_00 and MM5_12. 15 Compare MM5 & WRF MM5_00 WRF_MM5_00 WRF_00 REN Coef MM5 D3 (9km) with GFS 80km, start at 00Z. WRF same conditions as MM5_00 WRF with GFS 40km Combination of MM5 most recent forecasts. Weigthed regression of REN forecast with observed data, every 6 hours 16
WRF & MM5 Wind Speed 10m LISBOA PORTO Top 3 LISBOA: 1º coef 2º WRF_00 3º MM5 Top 3 PORTO: 1º coef 2º WRF_MM5 3º WRF_00 17 WRF & MM5 Temperature 2m LISBOA PORTO Top 3 LISBOA: 1º coef 2º MM5 3º WRF_MM5 Top 3 PORTO: 1º coef 2º MM5 3º WRF_00 18
Conclusions Caution: Studied only 1st trimester of 2007 MM5 Eolic: The best prediction is clearly coef (RMSE = 45 MW (6% total)) However, if real-time observed data is not available, multi-regressing the 11 available predictions for each hour is the second best choice (reg) (RMSE=72 MW (10% total)) A small improvement of REN is verified at day-night transitions, where all pure numeric forecasts behave best. This suggests diurnal corrections. REN could be combination of only MM5_00 and MM5_12 (which have improved boundary conditions from GFS) WRF & MM5: WRF 80 km < MM5 80 km < WRF 40 km MM5 is best for temperature because is more tunned to the site. 19