This work investigates the performance of a Neural Network based
hourly load forecasting system. Tests are made varying the
forecasting leading time from 1 to 744 hours ahead. Forecasting
electric load for long periods ahead (Le, over 24 hours) requires
the Neural Network to feed itself with predicted load values
(multii-step prediction) in order to forecast the next period. The
results obtained in these tests are very good when compared with
single-step prediction, which uses only the actual load values
available for the next prediction. This feature is a key result to
power systems operation since it allows accurate prediction with
large leading times.
In the experiments we use real load data from the Electric State
Company of Minas Gerais (CEMIG) and predict load for a whole
year (from March/1993 to Februasyll994). The results are
evalucxted using three error figures: WE (Mean Absolute
Percentage Error), FWSE (Root Mean Squared Error) and Theil's U
(rate between the FWSE of the actual forecasting system and the
RMSE of a naive forecasting system). In many cases, results
exhibit a MAPE below 2%. Temperature and other weather data
are not considered in these predictions.
kewords : Neural Networks, Load Forecasting, multi-step,
Backpropagation, auto correlation