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
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.
Available from: Ugo Ghisla
- "We have demonstrated the feasibility of the proposed approach by a simulation-based comparison of MVDC system operation with and without the protection operation system in place. Preliminary results of this comparison were presented in . Now, we analyze the stability of a DC system during load fault and voltage transients and show that this approach leads to an increase in the system stability. "
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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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ABSTRACT: The rapid advancement of complex, compact and efficient technologies in power systems (DC breakers, power converters, superconducting fault limiters, etc.) has allowed new concepts associated with marine electrical architectures and power systems to become reality. Advances in this area will facilitate cheaper, lighter, more efficient and future-proof electrical architectures, with DC zonal systems attracting a high level of interest. Such architectures will offer far greater levels of flexibility, redundancy and survivability compared to their AC counterparts. This paper investigates the possibilities of different marine electrical system architectures that may be used in future and presents the relative advantages and potential disadvantages associated with each. Research has focussed on moving from the predominantly used AC radial distribution systems towards DC zonal distribution in order to achieve the potential benefits previously stated. The use of a DC zonal architecture on future marine power systems will be reviewed and assessed, with regards to differing layouts and protection schemes. Major issues with protection and control of such designs will be studied and current solutions that have been proposed by others will be reviewed. Future aims of the research project in terms of development, simulation and testing of feasible solutions will also be discussed.
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