Stability of the Small-Scale Interconnected DC Grids via Output-Feedback Control

A decentralized nonlinear model and controller is proposed to stabilize the interconnected small-scale islanded dc grids in the presence of renewable energy sources with proven stability in this paper. The dc interconnected network comprises dc sources along with resistive and constant-power loads (CPLs). Though the dc sources are photovoltaic (PV) in this paper, the proposed controller can be applied to other types of lowinertia intermittent sources as well. All sources and/or CPL loads are connected to the grid through simple dc-dc converters (DDCs) to avoid power electronic complexities. The negativeresistance CPLs can destabilize the grid in the presence of the DDC dynamical components. The decentralized nonlinear output-feedback controller mitigates rapid voltage and power oscillations caused by the disturbances and measurement noises, and stabilizes the grid. Since the proposed output-feedback controller needs only partial knowledge of the local converter states, the number of measure points reduces leading to a simple implementation. Simulation results on a small-scale dc grid are provided to show the performance of the proposed controller.