Soft Start Algorithm for a Droop Controlled dc Nanogrid

Abstract

Droop control with the dc bus signaling is a well-known and widely studied decentralized control method for dc nanogrids but there are only few papers addressing the startup process of the dc nanogrid. The main challenge here is to safely manage big amount of capacitance available on the dc bus of the nanogrid. During startup the capacitors are uncharged and provide low impedance path for the startup current. This leads to dangerous overcurrents that could damage semiconductor switches and reduce the lifespan of the dc-link capacitors. Therefore, it is important to limit the inrush current. Since there are only few papers describing this issue, the goal of this paper was to fill this gap. Moreover, this work provides an overview of possible soft start scenarios suitable for the droop-controlled dc nanogrid. Computer models and simulations will be used to analyze hard start problems and verify a proposed soft start strategy.