Line-Independent Plug-and-Play Controllers for Voltage Stabilization in DC Microgrids

We consider the problem of stabilizing voltages in Direct Current (DC) microgrids given by the interconnection of Distributed Generation Units (DGUs), power lines, and loads. We propose a decentralized control architecture where the primary controller of each DGU can be designed in a plug-and-play fashion, allowing the seamless addition of new DGUs. Differently from several other approaches to primary control, local design is independent of the parameters of power lines and the only global quantity used in the synthesis algorithm is a scalar parameter. Moreover, differently from the plug-and-play control scheme in [1], the plug-in of a DGU does not require to update the controllers of neighboring DGUs. Local control design is cast into a linear matrix inequality problem that, if infeasible, allows one to deny plug-in requests that might be dangerous for microgrid stability. The proof of closed-loop stability of voltages exploits structured Lyapunov functions, the LaSalle invariance theorem and the properties of graph Laplacians. Theoretical results are backed up by simulations in PSCAD.