Connected to the electricity grid plug-in electric vehicles (EV) could be charged according to their user’s needs but at the same time providing benefits in the value chain of the electric power system, notably in generation, transmission and distribution. In an unbundled system with free access to liberalized energy and capacity markets, different electricity sector agents could be involved in enhancing and valuing intelligent charging alternatives of the vehicles’ storage capacity. The agents will look for their own profit maximization and if regulation is correctly designed the global optimum can be achieved. Building upon a conceptual regulatory framework that defines a set of possible scenarios in which EV could be charged; this paper shows the interactions of an existing agent, the unbundled distribution system operator (DSO) and a future new agent in electric power system, the electric vehicle aggregator. Each agent’s objectives and functions are presented for charging electric vehicles in two different deterministic schedules: dumb charging occurring coincident to peak system load and valley charging as a smart approach. First, the analysis turns to the different aspects of reselling energy by looking at three alternative pricing schemes of the aggregator to the final customer: dynamic hourly pricing, time-of-use tariff and a flat energy rate and then the DSO as a regulated entity is analysed looking to postponing network investments. In a simple case study, the benefits of charging the vehicles during low price night hours are quantified in terms of energy trading and deferring network investments. Depending on the final customer tariff chosen the annual value per vehicle of charging in valley hours amounts to 53.98 € to the aggregator, while it ranges around 55.17 € to the network operator. Therefore it can be concluded, that the value is in the same order of magnitude as the DSO being a regulated agent as it is to the aggregator being a commercial entity who is in charge of setting prices, which can be argued to be very perceptible incentives to economically sensitive demand elastic final customers. The different pricing options of the aggregator affect the benefit sharing between itself and the vehicle users. In the presented cases, the load in the local distribution system being very much correlated with the system load reflected in market prices, there are generally no conflicts of interest between the main agents involved in facilitated controlled charging to the fleet of vehicles, i.e. the electric vehicle aggregators and DSOs. It remains an interesting topic to construct such scenarios of diverging incentives and work on benefit sharing mechanisms as well as procedures to ask for load reductions by the distribution system operator.
Keywords: Distribution System Operator (DSO); Plug-in Electric Vehicle Supplier Aggregator (EVSA); Battery; Electric Vehicle; Regulation; Vehicle-to-Grid (V2G); Demand Response; Profit Optimization;
Cigrè International Symposium on The Electric Power System of the Future: Integrating Supergrids and Microgrids. Bolonia, Italia.13-15 Septiembre 2011
Published: September 2011.