Protection of medium voltage DC power systems against ground faults and negative incremental impedances

Widespread concern about how to protect DC power distribution systems against high fault currents, and how to compensate for instabilities brought on by constant power load characteristics, has prompted us to develop a new approach for protecting these systems. Our approach employs a compact multiple switching topology converter, which fulfills three functions: it limits the line current to a predetermined value (which could be dynamically set); it works as buffer during short-duration faults on the power bus; and it compensates load instabilities that could arise due to the constant power characteristic of a load. The structure of the protection circuit, its positioning in the distribution network, its possible configurations, control strategies, and parameters selection will all be shown. Analysis of the performances and feasibility of the approach will be presented.