Market-based coordinated charging of electric vehicles on the low-voltage distribution grid

This paper presents a market based coordination mechanism for charging electric vehicles. In market based coordination, a virtual market is used to match supply and demand of a commodity. The goal is to limit the impact of the electric vehicles on the low voltage distribution grid. First it is shown how, in general, the trading volume on a commodity market with a single supplier can be controlled by the shape of the bid function of the supplier. This approach is then translated to an electricity market where the transformer is the single supplier and the households and electric vehicles are the buyers of electricity. A number of test-scenarios are created with a reference distribution grid in which several vehicles are plug-in hybrid electric or fully electric. Load flow analysis shows that if no coordination takes place, the peak load exceeds the tranformer´s rating and the voltage drops below the norm. Simulations show that the market-based coordination mechanism is indeed capable of reducing the peak load to an acceptable level and keeps the under-voltage within an acceptable range.