Conference Paper

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

Dept. of Electr. Eng., Univ. of South Carolina, Columbia, SC, USA
DOI: 10.1109/SECON.2010.5453874 Conference: IEEE SoutheastCon 2010 (SoutheastCon), Proceedings of the
Source: IEEE Xplore

ABSTRACT 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.

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    ABSTRACT: We present a new approach for protecting DC power distribution circuits against faults and negative incremental impedance instabilities. Like a circuit breaker, the device is passive until a fault occurs. Unlike a circuit breaker, the device operates in current limiting mode or in impedance transformation mode, according to the system requirements, and it can serve as a power buffer during transient upstream disruptions. The approach permits coordination between hierarchical levels of protection, it enables system reconfiguration, and it increases system stability. All three types of protection are achieved automatically by the controller based solely on local current and voltage measurements. The efficacy of this solution has been demonstrated through simulation. System stability with and without the proposed protection system has been analyzed according to the Brayton-Moser mixed potential criterion. The approach is proven to increase the stability of the systems in all configurations.
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