Short term wind speed forecasting using ARIMA model
The massive integration of wind power into the power system increasingly calls for better short term wind speed forecasting which helps transmission system operators to balance the power systems with less reserve capacities. The time series analysis methods are often used to analyze the wind speed variability. The time series are defined as a sequence of observations ordered in time. Statistical methods described in this paper are based on the prediction of future wind speed data depending on the historical observations. This allows us to find a sufficiently good model for the wind speed prediction. The paper addresses a short term wind speed forecasting ARIMA (Autoregressive Integrated Moving Average) model. This method was applied for a number of different prediction problems, including the short term wind speed forecasts. It is seen as an early time series methodology with well known limitations in wind speed forecasting, mainly because of insufficient accuracies of the hourly forecasts for the second half of the day ahead forecasting period. The authors attempt to find the maximum effectiveness of the model aiming to find: (1) how the identification of the optimal model structure improves the forecasting results and (2) what accuracy increase can be gained by reidentification of the structure for a new wind weather season. Both historical and synthetic wind speed data representing the sample locality in the Baltic region were used to run the model. The model structure is defined by rows p, d, q and length of retrospective data period. The structure parameters p (Autoregressive component, AR) and q (Moving Average component, MA) were determined by the Partial Auto Correlation Function (PACF) and Auto Correlation Function (ACF) respectively. The model's forecasting accuracy is based on the root mean square error (RMSE) mean absolute percentage error (MAPE) and mean absolute error (MAE) The results allowed to establish the optimal model structure and the length of the input/retrospective period. The quantitative study revealed that identification of the optimal model structure gives significant accuracy improvement against casual structures for 6 8 h forecast lead time, but a season specific structure is not appropriate for the entire year period. Based on the conducted calculations, we propose to couple the ARIMA model with any more effective method into a hybrid model.