A microgrid is an integrated system consisting of interconnected loads and distributed energy sources with a clear entity boundary, operated in either islanded mode or grid-connected mode. Among the many challenges in microgrid operation, frequency and voltage (f-V) control (or, active and reactive power [P-Q] control) is one of the most challenging tasks. Many previous works in microgrid control use the trial-and-error approach to develop the proportional-integral-derivative or proportional-integral control gains, which are critical to microgrid stability and control. However, this trial-and-error approach is very time consuming, and the control parameters for the optimal performance at a given operating point may not be effective at other operating points, such as those seen with a change in microgrid operation mode, a new solar photovoltaic (PV) installation, or a reconfiguration of the network.

With all these challenges, a model-free adaptive control (MFAC) for microgrid V-f regulation in islanded mode or P-Q regulation in utility-connected mode, in which the maximum power point and state of charge of the battery were considered. The features and advantages of the model-free adaptive control include: 1) it is based on measurement, rather than the microgrid system model. Thus, it is model-free and suitable for real-time applications, scalable to different sizes of microgrid with different numbers of devices, and portable to other microgrids. 2) The control gains are self-adjustable to track a pre-defined, desired trajectory such that a fast and smooth response can always be achieved to match the desired trajectory, regardless of external changes (load levels, distribution network, or solar PVs), designer experience for initial control gains, or any offline training studies. Therefore, it achieves the plug-and-play capability for microgrid V-f or P-Q regulation.

The performance of the MFAC algorithm for microgrids was verified. Active and reactive control (P-Q control), as well as f-V control, are two of the challenging tasks in microgrid operation. This project developed MFAC for both P-Q and f-V control in microgrids. The performance of the algorithm was verified in MATLAB-Simulink, which has been included in the control algorithm performance report. In the project Final Report, the algorithm is further validated through a hardware-in-the-loop experiment in Center for Ultrawide Area Resilient Electric Transmission Networks Hardware Testbed. Through the results from simulation and hardware test, the efficiency of the proposed MFAC algorithm is verified.

The plug-and-play characteristics of this control make the integration of distributed energy resources, battery storage, and coordinating different types of generators much easier than before. With this control approach, the U.S. military can save costs by switching its bases from diesel backup generators to more efficient microgrids with distributed renewable energy generation and storage. Moreover, the military can protect its mission critical loads, benefiting from the added resilience at a much-reduced cost. (Project Completion - 2024)