Low-dimensional space- and time-coupled power system control policies driven by high-dimensional ensemble weather forecasts

Many predictive control problems can be solved at lower cost if the practitioner is able to make use of a high-dimensional forecast of exogenous uncertain quantities. For example, power system operators must accommodate significant short-term uncertainty in renewable energy infeeds. These are predicted using sophisticated numerical weather models, which produce an ensemble of scenarios for the evolution of atmospheric conditions. We describe a means of incorporating such forecasts into a multistage optimization framework able to make use of spatial and temporal correlation information. We derive an optimal procedure for reducing the size of the look-ahead problem by generating a low-dimensional representation of the uncertainty, while still retaining as much information as possible from the raw forecast data. We then demonstrate application of this technique to a model of the Great Britain grid in 2030, driven by the raw output of a real-world high-dimensional weather forecast from the U.K. Met Office. We also discuss applications of the approach beyond power systems

Machine learning and robust MPC for frequency regulation with heat pumps

With the increased amount of volatile renewable energy sources connected to the electricity grid, there is an increased need for frequency regulation. On the demand side, frequency regulation services can be offered by buildings that are equipped with electric heating or cooling systems, by exploiting the thermal inertia of the building. Existing approaches for tapping into this potential typically rely on a first-principles building model, which in practice can be expensive to obtain and maintain. Here, we use the thermal inertia of a buffer storage instead, reducing the model of the building to a demand forecast. By combining a control scheme based on robust Model Predictive Control, with heating demand forecasting based on Artificial Neural Networks and online correction methods, we offer frequency regulation reserves and maintain user comfort with a system comprising a heat pump and a storage tank. We improve the exploitation of the small thermal capacity of buffer storage by using affine policies on uncertain variables. These are chosen optimally in advance, and modify the planned control sequence as the values of uncertain variables are discovered. In a three day experiment with a real multi-use building we show that the scheme is able to offer reserves and track a regulation signal while meeting the heating demand of the building. In additional numerical studies, we demonstrate that using affine policies significantly decreases the cost function and increases the amount of offered reserves and we investigate the suboptimality in comparison to an omniscient control system.Comment: 13 pages, 12 figures, 1 table, submitted to IEEE Transactions on Control Systems Technolog