Towards Plug-and-Play Microgrids

Droop-controlled inverters are thought to be an excellent interface for distributed generation of future power grids. Ease of installation, fully decentralized power sharing and simple procedures for expansion/reconfiguration make this type of control attractive for practical applications, in particular for microgrids. However, such microgrids appear to exhibit instabilities severely limiting the allowed ranges of control settings. Moreover, modelling approaches based on time-scale separation, that were successfully used for decades for stability assessment of conventional power systems, appeared to be inappropriate for microgrids, calling for new methods, specific to microgrids, to be developed. In this paper, we present a method for tuning inverter control parameters (namely droop coefficients and virtual impedance) that guarantees stable operation under arbitrary interconnection of inverters to the grid. The proposed method lays the foundation for plug-and-play architectures for inverter-based microgrids.