DC fault performance and cost analysis of DC grids for connecting multiple offshore wind farms

2015 IEEE Power &Amp; Energy Society General Meeting

Taherbaneh

Taisne

et al. 2015

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Abstract-This article presents a topology for DC grids which enables very robust DC fault protection with moderate costs, good operating flexibility and simple controls. It is postulated that radial DC systems are best suited for limited-size local DC grids. Radial topology enables robust and fast protection selectivity using only local signals and exploiting the advantages of hybrid DC circuit breakers. To enable flexible expansion options to national/international systems, it is suggested to interconnect star points of radial systems using DC/DC converters. DC/DC converters enable inherent isolation of DC faults and provide firewall between radial DC grids. Each interconnecting cable is protected by a DC/DC at one end and a hybrid Circuit Breaker at the other end. The control options for DC/DC converter and the radial grids are analysed. A detailed simulation model of 6 terminal DC grid with 2-star points is presented. The PSCAD simulation results confirm DC fault isolation and good control performance of the proposed topology for a range of DC fault contingencies.

Section: A Topology and Protectionmentioning

confidence: 99%

“…The use of DC/DC converter as a DC circuit breaker has been proposed [7]- [9]. DC/DC converters enable ideal isolation of two DC systems since they will not propagate DC faults.…”

Section: Introductionmentioning

confidence: 99%

Offshore DC grids as an interconnection of radial systems: Protection and control aspects

2015 IEEE Power &Amp; Energy Society General Meeting

Taherbaneh

Taisne

et al. 2015

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“…It will be very difficult to connect two DC transmission systems from different vendors by using only DC CBs. To solve the above mentioned challenges, the use of DC/DC converter has been proposed [6]. DC/DC converters enable isolation of two DC systems since they will not propagate DC faults.…”

Section: Introductionmentioning

confidence: 99%

“…Reference [6] compares costs of simple DC grids with DC CBs versus grids with DC/DC converters. It is concluded that overall costs are similar since large number of DC CBs will perform similarly as small number of strategically located DC/DC converters.…”

Section: Introductionmentioning

confidence: 99%

Developing regional, radial DC grids and their interconnection into large DC grids

2014 IEEE PES General Meeting | Conference &Amp; Exposition

Taherbaneh

Taisne³

et al. 2014

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The development of future DC grids has high importance for future EU energy policy, but the technologies and DC grid topology are still uncertain. This article studies the concept of building large DC grids as an interconnection of regional radial DC systems. The radial topology enables very simple and robust DC system protection. It is not feasible to directly connect radial systems using DC cables because of requirements for protection system communication and associated delays. DC/DC converters offer possibility to interconnect two regional DC systems avoiding protection issues. Simulation tests are performed on detailed model of 2, 3-terminal radial DC grids interconnected using DC/DC converter. A fault on any radial cable is isolated using a local DC CB. A fault on interconnecting cable is isolated using DC/DC and a DC CB, without affecting operation of the other regional DC grid. It is concluded that the proposed method could be adopted to build very large DC grids which will satisfy high power transfer security standards.

“…DC/DC converters might become crucial elements to facilitate a meshed DC grid. The downside of the DC/DC converters is they have approximately 180%-200% VSC converter costs, implying that the number of converters and their location should be critically evaluated [5].…”

Section: Introductionmentioning

confidence: 99%

Interconnecting subsea DC collection systems into a high reliability DC grid

Zhang

IEEE PES Innovative Smart Grid Technologies, Europe

2014

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This paper presents a subsea DC collection grid with robust control and protection scheme and flexible expansion capability. By virtue of the DC/DC converter, different sections of the subsea grid are functionally interconnected and in the meantime decoupled in the event of DC faults. The faults are selectively isolated and system recovery from the faulty DC intertie branch is achieved by a coordinated operation on DCDC converters and DC disconnectors (or standard AC circuit breakers). A test system is presented which consists of two 100MW renewable energy sources and DC collection/transmission grids. The simulation results confirm the N-1 security of the presented topology and good control performance over DC faults.