MoMeWEC – Modular Megawatt-range Wireless EV Charging Infrastructure Providing Smart Grid Services

 

MoMeWEC proposes a compact solution for large-scale electric vehicle (EV) charging based on modular multilevel converter (MMC) and inductive power transfer (IPT) charging technologies.

 

Compact solution for large EV charging facilities in space-constrained areas

Electric vehicles are gaining global acceptance thanks to the increasing public awareness and ambitious environmental goals. Some developed countries have already achieved significant EV adoption rates. For example, it is reported that more than half of all purchased vehicles in Norway in 2018 were plug-in EVs. This trend is expected to diffuse across the world in the next years.

Increasing number of EVs will increase the demand for large-scale EV charging facilities to charge numerous cars simultaneously especially in space-constrained urban areas. A megawatt level charging facility typically requires connection to medium voltage (MV) grid through several transformers. Also dimensioning low voltage (LV) cables for very high currents results in heavy, space-consuming and expensive cabling. Innovative solutions will be needed to minimize the electrical equipment costs and space requirement in megawatt range charging infrastructures.

MoMeWEC aims at developing a compact solution for high-power charging stations with minimum space requirements. The system configuration proposed is based on MMC technology that eliminates the requirement of a MV/LV transformer and reduces cabling complexity. This configuration would offer the dual advantages of saving space and reducing installation and equipment costs significantly. Furthermore, the application of wireless IPT-based charging units in the proposed topology assures inherent galvanic isolation between the vehicle and the power conversion system.

International Research Cooperation

MoMeWEC is a joint project with partner organizations from countries that have complementary needs and opportunities in the field of electric vehicles. Germany and Japan have leading automotive industry that made significant progress in EV technologies. Japan is a unique case that necessitates compact EV charging solutions due to the extreme population density in its urban areas. With highest adoption rate in electric cars, Norway represents an ideal test-bench for real-world deployment of innovative charging solutions. Furthermore, each involved group has expertise in different but complementary fields.

• SINTEF Energi AS, Norway (Coordinator): Advanced grid connection techniques for high-power converters
• University of Tokyo, Japan: Wireless power transfer to EVs
• Nagaoka University of Technology, Japan: Multilevel converter design and control
• RWTH Aachen University, Germany: Optimization for energy management and real time simulation

Technical challenge

MMC based configuration would be the optimal solution for big EV charging parks if it assures grid stability. In effect, the MMC system must behave as a three-phase balanced load for a stable grid operation. However, due to the heterogeneous presence of EVs and different individual charging needs, the loading on MMC cells will often present an uneven distribution, which will lead to unbalanced three phase currents at the grid interface unless the power flows within the MMC arms are controlled.

   

Role of Institute for Automation of Complex Power Systems (ACS)

Smart car allocation in the charging park and scheduling for EV charging are essential to minimize the power control challenges and consequently maximize the benefits of MMC based charging infrastructure. ACS will transfer its expertise in optimization algorithms for energy management applications to MoMeWEC with the goal of developing a car allocation and charging strategy that assures optimal loading distribution on MMC units throughout the charging period of cars. Furthermore, ACS will validate the developed charging strategy and MMC control approach through real-time simulation and control-hardware-in-the-loop technique.

Acknowledgment

MoMeWEC is a research project that is funded under the international joint initiative EIG CONCERT - Japan. Grateful acknowledgement is made to BMBF (German Federal Ministry of Education and Research) for providing financial support.

     

Announcements

An article on "Optimal Management for Megawatt Level Electric Vehicle Charging Stations with a Grid Interface Based on Modular Multilevel Converter" has been published in "IEEE Access". The article is available for open access.

 

An article on „Optimal load management strategy for large electric vehicle charging stations with undersized charger clusters” has been published in “IET Electrical Systems in Transportation”. This work is the main output of the joint research conducted by SINTEF Energy Research and ACS under MoMeWEC project. The article is available for open access at the link.