Breaker technologies for DC power grids: research seeks a solid-state solution

July 01, 2014 // By Graham Prophet
In a joint announcement from the partners in the “NEST-DC”research project – Airbus Group, E-T-A Elektrotechnische Apparate, Infineon, Siemens, and University of Bremen – the research objectives of the project are set out as developing an innovative electronic circuit breaker for renewable energy and on-board grids

According to a statement released by Infineon, Direct current offers many advantages compared to the conventional alternating current used today: For example, losses in power grids and electric devices are a total of 5 to 7% smaller than with alternating current. Direct current also makes it possible to more efficiently feed electric energy from regenerative sources into power grids and energy storage and to improve grid stability; with direct current it would be possible to build much more compact electric devices.

In the past the lack of efficient and cost-effective circuit breaker technologies has made it impossible to fully exploit the potentials of direct current, e.g. in distribution grids in data centres, photovoltaics and telecommunication systems or in on-board grids for aviation and shipping, electric vehicles and railway technology. The only electromechanical circuit breakers available today carry the risk of arcing when switching direct current and voltages; furthermore they are slow to react, heavy, unwieldy and expensive.

Funded by the German Federal Ministry of Education and Research (BMBF), the “NEST-DC” research project aims to investigate the foundations of an innovative semiconductor-based and completely electronic circuit breaker for DC power grids and applications. The new circuit breaker should be able to switch direct current on, and most importantly switch it off, as quickly and safely as possible at voltages of up to 1,500V. Among other things NEST-DC will explore innovative semiconductor components such as the Over Current Blocking Field Effect Transistor (OCB-FET). New structure and connection technologies and switching topologies for the circuit breakers that will use OCB-FETs are to be formulated and tested. There will be demonstrators for the project results in the areas of on-board aviation grids, electromobility and photovoltaics, as well as for direct current distribution networks.

NEST-DC research partners represent the complete value creation chain from the semiconductor chip all the way to the DC power grid system. The team includes the University of Bremen's Institute for