Model-Based fault current estimation for low fault-energy 380VDC distribution systems

Abstract

380 V <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DC</sup> distribution grids have reached maturity for the power supply of data centers and central offices over recent years. New developments in this field are tending towards integrating more distributed energy resources like photovoltaics and wind turbines. Also, high-capacity battery storage systems based on lithium-ion cells are on the rise to increase self-reliance and reduce operating cost. With every grid component being connected to the 380 V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DC</inf> supply bus via a DC/DC or AC/DC converter, the dynamic system behavior will be entirely dominated by the control loops and operational limits of the power electronic components. In consequence, a re-evaluation of the fault current propagation for various fault types is necessary to dimension safety devices correctly. This paper describes a modelling approach using linearized converter models to analyze the system behavior. The presented models are verified with a laboratory test grid. Finally, guidelines to properly select safety elements and setting up self-protecting mechanisms for power converters in next generation 380V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DC</inf> distribution grids are outlined.