Despite benefiting from AC systems for more than a century, there are applications where DC technology is preferred and is already deployed or considered. Potentials and benefits are largely unexplored in the medium voltage (MV) domain due to lack of available high-power conversion and protection technologies for DC. Project focus was on novel, compact and highly efficient power electronic conversion technologies for MVDC applications that provide benefits on the system level. System level stability studies are used to aid system design and ensure safe and reliable operation.
To enable deployment of MVDC power distribution networks, various conversion and protection technologies have to be developed from the scratch or adapted from the existing MVAC systems. While the existing MVAC distribution grids are widely spread, both in utility and industrial applications, MVDC power distribution networks are currently considered for some specific applications, such as: electric ship distribution, photovoltaic and wind plants collection grids, data centres, etc. Industry is currently at the stage of feasibility assessment, which provides great research opportunities to define and shape further developments in the area.
While the focus of the research activities in the first year of the project was mostly on development of enabling conversion technologies suitable for MVDC, the second year focus has been on performance verifications and translation of concepts towards the working prototype. In addition, system level stability studies have opened several other research directions related to active impedance/admittance shaping through control means, as well as area of real time impedance/admittance measurements for medium voltage systems. The last year has been focusing on the key activities that allow us to consider that we reach the main objectives of the project. In that sense, the format of this report has been elaborated to show, objective by objective how the milestones of the project have been achieved.
Industrially sponsored part of the project, has moved its initial focus from high power marine electrical systems, towards the more generic MVDC architectures, inspired by other industrial installations involving multiple high power sources and loads, interconnected by MVDC electrical power distribution.
SCCER-FURIES research activities related to MVDC-LVAC conversion have led to a proposal of a Galvanically Isolated Modular Converter (GIMC) characterized by single stage, galvanically isolated converter relying on the modular multilevel converter principles. Since SCCER round 1 of financing is over and considering lack of dedicated funds for hardware demonstrators, GIMC prototype has not been completely finalized. We are continuing our activities within the SCCER round 2 of financing, where platform will be finalized (largely thanks to our internal funds), and be used to support activities related to high power DC-DC conversion based on GIMC platform. SNSF NRP70 part of the research related to MVDC-LVDC conversion, resulted in development of a concept of Multiport Energy Gateway (MEG) – a modular and isolated multiport DC-DC converter that integrates distributed storage elements. Prototype is currently being assembled for the final testing and demonstration of developed principles. The SNSF project Solid State Resonant Conversion (SSRC) with focus on the high power DC-DC conversion using Integrated Gate Commutated Thyristors (IGCT), has developed high power test setup, and we are actively gathering experimental data. All these research activities require galvanic isolation by means of medium frequency transformers, and receive support from internally funded research activities in this domain.
Several research papers have been either already published or submitted, as provided in the list at the end of a report.
