Cost-efficient integration of electric vehicles with the power grid by means of smart charging strategies and integrated on-board chargers

Electric vehicles (EVs) are new type of additional load on the power grid. The change of the load profile depends on the penetration level of EVs as well as on the used charging strategies. State-of-the-art charging strategies such as dumb charging and dual tariff charging are not the appropriate solutions for charging EVs. Both strategies causes peak demands which could induce violations of the power grid constrains. Hence, smart charging is necessary to reduce peak demands and to realise valley-filling. Furthermore smart charging in many cases is based on a novel smart power grid infrastructure. The major objectives of smart charging are the minimisation of the electricity costs of consumers and the cost-efficient update of the power grid infrastructure. In addition, all EVs have to be equipped with a bidirectional on-board charger which enables vehicle-to-grid (V2G) capability. This type of charger consists of a combined AC/DC rectifier and DC/AC inverter. The most efficient solution is to integrate the charger in the already existing propulsion machine inverter. The major objectives of an integrated on-board charger are the minimisations of manufacturing costs, maintenance costs and weight of the EV. In this paper several smart charging strategies as well as charger topologies are presented and assessed.