Pietro Cairoli, Debrup Das, Luca Raciti, and Antonello Antoniazzi
All-electric commercial ships are becoming more popular and DC is the onboard power distribution system of choice thanks to its ability to handle large power flows in a confined space with high system efficiency and low life cycle cost [1].
Commercial vessels with an onboard DC grid have been proven to operate at the highest energy efficiency level while minimizing emissions. This enables significant power savings and lower operational cost for marine applications from cargo to cruise ships [2]. Figure 1 Illustrates an example of a DC distribution system for commercial vessels.
The power requirements and performance of the DC system are predicated on very fast fault protection to provide protection selectivity, high survivability and reconfigurability after a fault event. Fault protection and isolation is in fact one of the remaining challenges of shipboard DC distribution systems [3].
Solid state DC circuit breakers (SS DCCB) can provide very short reaction time and fast current interruption up to 1000 times faster than electromechanical circuit breakers thanks to the properties of power semiconductor devices. ABB developed a solid state DC circuit breaker with extremely low conduction losses, high power density and ultra-fast reaction time that meets the challenging requirements of protection for shipboard DC distribution systems.
The solution is based on the parallel connection of Si reverse blocking IGCT (RB-IGCT), which is a custom semiconductor device that was optimized for low-losses, developed by Corporate Research and ABB Semiconductors in Lenzburg, and optimized metal oxide varistor (MOV). The RB-IGCT is 1000 times faster than any electromechanical contact and has been optimized for low conduction losses [4]. The optimized MOV enables dissipation of high system inductive energy with fast current interruption and isolation time.
The high current solid state DC circuit breaker has revolutionized system protection for safe, arc-less, high-efficiency DC systems. The developed platform targets system voltage up to 1000 Vdc and nominal currents with a range from 1000 A to 5000 A. The technology features efficiency as high as 99.8% compared to 99.5% found in solutions that are based on Si IGBT technology. The solid state breaker can be cooled both with water for supreme power density and with advanced two-phase cooling, which delivers the simplicity of air cooling and performance close to liquid cooling, ensures low installation and maintenance costs and long asset life.
Benefits of the new technology are impressive and will enhance performance of electrical transportation, renewable energy solutions, and industrial battery storage [5].
Power losses are 70 percent lower than comparable solutions, enabling savings of up to $200,000 in a ferry and up to $1 million in a cruise liner over a ten-year period. The new breaker can also be used in numerous other applications such as grid-connected battery energy storage systems, data centers and electric vehicle charging infrastructure. In fact, ABB won project funding from the US Department of Energy to develop DC breakers for EV charging applications. The solid state circuit breaker will make electrical distribution systems more reliable and efficient and will drive down maintenance costs while meeting the durability demands of next-generation electrical grids.
ABB plans to introduce the first commercial application of the DC breaker in 2020.
References
[1] ABB. (2013). ABB Delivers First Onboard DC Grid System. [Online]. Available: http://www.abb.com/cawp/seitp202/7199db5e8cd3924e85257b3b00491f07.aspx
[2] ABB. (2014). Test Confirm Up to 27% Fuel Savings on Ships from Onboard DC Grid. [Online]. Available: http://www.abb.com/cawp/seitp202/6f0d5472c16d3fc4c1257cf9002661ed.aspx
[3] P. Cairoli, R. A. Dougal, “New Horizons in DC Shipboard Power Systems: New fault protection strategies are essential to the adoption of dc power systems”, IEEE Electrification Magazine, Vol. 1, No. 2, pp. 38-45, December 2013
[4] U. Vemulapati, M. Arnold, M. Rahimo, A. Antoniazzi, “2.5kV RB-IGCT Optimized for Solid State Circuit Breaker Applications,” in Proc. 2014 International Seminar on Power Semiconductors, Prague, Czech.
[5] ABB reinvents the circuit breaker - https://new.abb.com/news/detail/18499/abb-reinvents-the-circuit-breaker-breakthrough-digital-technology-for-renewables-and-next-gen-power-grids
