Model-free estimation of available power using deep learning

Abstract. In order to assess the level of power reserves during down-regulation, the available power of a wind turbine needs to be estimated. The current practice in available power estimation is heavily dependent on the pre-defined performance parameters of the turbine and the curtailment strategy followed. This paper proposes a model-free approach for a single input, dynamic estimation of the available power using recurrent neural networks. The unsteady patterns in the turbulent flow are represented via Long Short-Term Memory (LSTM) neurons which are trained during a period of normal operation. The model-free approach requires only 1-Hz wind speed measurements as the input and generates 1-Hz available power estimation as the output. The neural network is trained, tested and validated using the DTU 10 MW reference wind turbine HAWC2 model under realistic atmospheric conditions. The adaptability of the network to changing inflow conditions is ensured via transfer learning, where the last LSTM layer is updated using new measurements. It is seen that the sensitivity of the networks to changing wind speed is much higher than that of turbulence, and the updates are to be implemented solely based on the altering inflow velocity. The validation of the trained LSTM networks on time series with 7, 9 and 11 m/s mean wind speeds demonstrates high accuracy (less than 1 % bias) and capability of transfer-learning. Including highly turbulent inflow cases, the networks have shown to easily comply with the most recent grid codes, which require the quality of the available power estimations to be evaluated with high accuracy (less than 3.3 % standard deviation of the error) at 1-min intervals.