Supervisory Control for Real Time Reactive Power Flow Optimization in Islanded Microgrids

A microgrid (MG) is a local energy system consisting of a number of energy sources, energy storage units and loads that operate connected to the main electrical grid or autonomously. MGs include wind, solar or other renewable energy sources. MGs provide flexibility, reduce the main electricity grid dependence and contribute to change the large centralized production paradigm to local and distributed generation. However, such energy systems require complex management, advanced control and optimization. Interest on MGs hierarchical control has increased due to the availability of cheap on-line measurements. Similarly to any process system, MG hierarchical control is divided into three levels. However, an additional control algorithm is required to manage power transmission between sources and loads, maximizing efficiency and minimizing transmission losses. This real-time optimization problem is addressed to locally readjust converters operation to attain global efficiency.
An algorithm is presented by formulating and solving the power sharing optimization problem in a two-level approach. The objective function is the sum of the apparent power transferred, whose minimization reduces total power losses and energy costs. The performance of the approach proposed is validated on a simulated case study. Different scenarios are tested and the performance of the algorithm is compared and discussed. The power losses reduction obtained with the proposed approach are compared with those obtained by standard procedures (Equal Power Sharing - EPS), showing enhanced performance.