High-voltage DC transmission and distribution could imply major gains over the use of AC. However, major barricade to the implementation of such plan is the absence of an effective and reliable circuit-breaker function. Every high current, when being interrupted by a physical gap, will cause an arc to strike. With the polarisation reversals of AC, arcs can be extinguished.

Work reported by partners in the research project "NEST-DC" describes research for DC power grids, establishing the technological basis for high performance electronic (as opposed to electromechanical) breakers.

The German research team has explored the technological basis for reducing the energy losses in power grids and electric devices by more than half through the use of DC. The five project partners from industry and science sector investigated the foundations of a semiconductor-based and completely electronic circuit breaker that can be used for future DC power grids and applications.

Collaboration for circuit breakers

The circuit breakers will be able to switch on direct current as fast and safely as possible and in case of emergency, switch it off in the shortest possible time. They will enable efficient feeds of energy from regenerative sources into power grids and energy storage, and will develop grid stability. With direct current it will also be possible to build more compact electric devices. Infineon Technologies was the team leader and worked on the circuit breakers together with Airbus, E-T-A Elektrotechnische Apparate, Siemens and the University of Bremen’s Institute for Electrical Drives, Power Electronics and Devices (IALB). The European Centre for Power Electronics provided further support. The ECPE is headquartered in Nuremberg, Germany.

The project partners explored innovative semiconductor components such as the Over Current Blocking Field Effect Transistor (OCB-FET). Structure and connection technologies were formulated and tested as well as switching topologies. The team built demonstrators for the project results in the areas of on-board aviation grids, electromobility and photovoltaics as well as for direct current distribution networks.

The IALB handled investigation and simulation of novel semiconductor structures for use in the Over Current Blocking Field Effect Transistor, static and dynamic measurement of the developed circuit breakers and testing their thermal behaviour and destruction limits. Airbus defined the requirements from an aviation point of view and developed a solution concept which was realized and demonstrated together with the NEST-DC partners.

Research funding

Siemens concentrated on the structure and connection technologies of the circuit breakers. E-T-A Elektrotechnische Apparate defined the requirements for industrial applications and, together with the partners, validated the circuit breakers for voltage classes up to 1,500V. Infineon contributed its power semiconductor expertise and researched power semiconductors intended for use in the OCB-FETs.

NEST-DC abbreviates the German for “Innovative Electronic Direct Current Circuit Breakers for Renewable Energies and On-Board Power Networks”. The research partners invested approximately ₹32.14 crore (€4.5million) during the course of the project. The project began in October 2013 and ran for three years. The German government set itself a goal of more efficiently using power in the future through the use of innovative power electronics. The German Federal Ministry of Education and Research (BMBF) are funding multidisciplinary research and development in the context of the ICT 2020 framework program on the topic of “Power Electronics for Increasing Energy Efficiency”. NEST-DC received approximately ₹15 crore (€2.1million) in support from the BMBF.

First published by EDN Europe.