Minimax Model Predictive Operation Control of Microgrids

Worldwide, the amount of decentralized renewable energy production is growing. The power infeed of many of these distributed sources fluctuates, depending on weather conditions. One way to cope with the changed, distributed structure and the increasing amount of fluctuations is to partition the grid into small electrical networks, called microgrids. To increase the reliability of supply, microgrids can be operated electrically isolated (i.e. islanded) from the grid, for example if problems within the transmission network occur. One of the main questions in this operation mode is: How to provide an optimal operation control scheme for microgrids with a high share of renewable energy sources (RES) that is robust to perturbations in load and RES infeed? To answer this question, an optimal control problem (OPC) that provides this properties in the presence of uncertain loads and RES infeed is presented. Assuming that the uncertainty is within a lower and upper bound along a given forecast, the problem is posed as a worst-case or minimax hybrid OPC, where the RES output can be curtailed. The OCP is formulated as a mixed-integer linear program that is solved online and applied in a receding horizon fashion. To compare the approach with a mean certainty-equivalent solution, a numerical case study is presented.