In recent years, the concept of nano- and micro-grids with DC-distribution networks has flourished, and it has become a common research area for power electronics and power systems. The DC grid can reduce the requirement of energy converting stages and cabling mass which has a positive impact on infrastructure cost and efficiency. Therefore, more often, the DC distribution grid is sought as a replacement for the typical AC distribution in high power data centres and IT systems, and it is finding the way into more electric transportation systems, e.g., maritime and aerospace sectors. Additionally, DC grids have great performance for the integration of different energy sources and large-scale energy storage, including rechargeable batteries and regenerative fuel-cell technologies. The reliability issues of the operation of DC grids due to faults is rapidly being mitigated, because the technology of solid-state circuit breakers is becoming mature and more efficient. However, power losses are still far from ideal, especially in high power grids where bipolar semiconductors are used. Guidelines and standardization for the transportation sector with respect to DC grids are still in its infancy and need strong synergies between the players from the field. In low-capacity DC distribution grids, it becomes challenging to solve the stability issues created by the multiple connections of power electronics systems where each one has unknown control settings.
The development of analytical and computational models for the grid and small-signal modelling are hot topics today, e.g., black-box modelling, digital twins, etc. Mitigation solutions for de-coupling of the interactions of the components such as the incorporation of short-capacity energy storage systems (as super-capacitors), and the proposal of non-linear control strategies are important topics of research. For the power electronics point of view, new design requirements for AC/DC converters for the energy generation, DC/AC for the electrical (or hybrid) propulsion, DC/DC converters for battery chargers, solar generation, and fuel-cell energy storage, among others, will affect the way we derive these systems. Their designs should feature circuit modularity and fault-tolerances, but light weights and power efficiency are particularly important to minimize the overall energy demand. Safety, reliability, and system integrations into the DC-distribution will impose strict regulations on how to select, control and design each subsystem. Therefore, the needed growth of more electric transportation introduces several new challenges, but through incorporation of smart components will enable digitalization techniques that can simplify maintenance and increase availability, and above all it creates new opportunities for research and entrepreneurship. The multitude of new power subsystems that need to be developed for E-transportation, requires a deep understanding of systems interactions. These new elements will play an important role on the quality (safety, weight, and cost) of the transport vessels, and the need time-to-market.
All in all, overcoming safety and economical challenges of more electric transportation has a great opportunity for the R&D of power electronics, electromagnetic compatibility, control methodologies, protection and power system integration in general.
Thiago Batista Soeiro, Universiteit Twente