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All over the world the reduction of greenhouse gas (GHG) emissions, especially in the transportation sector, becomes more and more important. Electric vehicles will be one of the key factors to mitigate GHG emissions due to their higher efficiency in contrast to internal combustion engine vehicles. On the other hand, uncoordinated charging will put more strain on electrical distribution grids and possible congestions in the grid become more likely. In this paper, we analyze the impact of uncoordinated charging, as well as optimization-based coordination strategies on the voltage stability and phase unbalances of a representative European semi-urban low voltage grid. Therefore, we model the low voltage grid as a three-phase system and take realistic arrival and departure times of the electric vehicle fleet into account. Subsequently, we compare different coordinated charging strategies with regard to their optimization objectives, e.g., cost reduction or GHG emissions reduction. Results show that possible congestion problems can be solved by coordinated charging. Additionally, depending on the objective, the costs can be reduced by more than 50% and the GHG emissions by around 40%.

The offshore wind resource is very large in many coastal regions, over 80,000 MW capacity in the region studied here. However, the resource cannot be utilized unless distant offshore wind generation can be effectively collected and brought to shore. Based on extensive oceanographic, environmental, and shipping data, a realistic wind energy deployment layout is designed with 160 wind power plants each 500 MW. The power collection and transmission infrastructure required to bring this power to shore and connect it to the electricity grid is designed and analyzed. Three types of connection to shore are compared; high voltage AC to the nearest onshore point of interconnection (POI), high voltage DC with voltage-source converter (HVDC-VSC) to the nearest onshore POI, and connecting to an offshore HVDC backbone running parallel to shore that interconnects multiple wind power plants and multiple POIs ashore. The electrical transmission losses are estimated step by step from the wind turbines to the POI. The results show that such a large system can be built with existing technology in near-load resources, and that losses in the HVDC-VSC systems are approximately 1%-2% lower than that in the AC system for a distance about 120 km from shore. INDEX TERMS Power system interconnection, transmission losses, high-voltage alternating current (HVAC), high-voltage direct current (HVDC), offshore wind power, transmission design.

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