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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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This article addresses the problem of estimating the potential economic and environmental gains for utility grids of shifting the electric-vehicle (EV) charging time and location. The current literature on shifting EV charging loads has been limited by real-world data availability and has typically therefore relied on simulated studies. Collaborating with a large automobile company and a major utility grid operator in California, this research used actual EV operational data and grid-operation data including locational marginal prices, marginal-grid-emission-rate data, and renewable-energy-generation ratio information. With assumptions about the future potential availability of EV charging stations, this research estimated the maximum potential gains in the economic and environmental performance of the electrical-grid operation by optimizing the time and location of EV charging. For the problem of rescheduling the charging sessions, the optimization models and objective functions were specifically designed based on the information available to the energy system operators that influence their economic and environmental performance like grid congestion, emissions, and renewable energy. The results present the maximum potential in reducing the operational costs and the marginal emissions and increasing the renewable energy use in the utility grid by rescheduling the EV charging load with respect to its time and location. The analysis showed that the objective functions of minimizing the marginal cost or the marginal emission rate performed the best overall.

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