Microgrids are a promising and viable solution for integrating the distributed generation resources in future power systems. Similar to large-scale power systems, microgrids are prone to a range of instability mechanisms and are naturally fragile with respect to disturbances. However, existing planning and operation practices employed in large scale transmission grids usually cannot be downscaled to small low-voltage microgrids. This talk will discuss the concept of ad-hoc microgrids that allow for arbitrary interconnection and switching with guaranteed stability. Although the problem of microgrid stability and control has received a lot of attention in the last years, vast majority of existing works assumed that the network configuration is given and fixed. Moreover, only few works have accounted for electromagnetic delays that will be shown to play a critical role in the context of stability.
The talk will introduce a new mathematical framework for characterization and certification of stability in an ad-hoc setting and derive the formal design constraints for both DC and AC networks. In the context of low-voltage DC network, the corresponding derivations will employ the Brayton-Moser potential theory and result in simple conditions on load capacitances that guarantee both small-signal and transient stability. Whereas for AC microgrids, the singular perturbation analysis will be used to derive simple relations for the droop coefficient of neighboring networks. The talk will conclude with a discussion of key open problems and challenges.