Abstract

Batteries of Electric Vehicles (EVs) and Plug-in Hybrid Electric Vehicles (PHEVs) have a large potential not only to provide energy for the locomotion of these vehicles, but also to interact, in dynamic way, with the power grid. Thereby, through the energy stored in the batteries, these vehicles can be used to regulate the active and the reactive power, as local Energy Storage Systems. This way, EVs can contribute to help the power grid to regulate the active and reactive power flow in order to stabilize the production and consumption of energy. For this propose should be defined usage profiles, controlled by a collaborative broker, taking into account the requirements of the power grid and the conveniences of the vehicle user. Besides, the interface between the power grid and the EVs, instead of using typical power converters that only work on unidirectional mode, need to use bidirectional power converters to charge the batteries (G2V - Grid-to-Vehicle mode) and to deliver part of the stored energy in the batteries back to the power grid (V2G - Vehicle-to-Grid mode). With the bidirectional power converter topology presented in this paper, the consumed current is sinusoidal and it is possible to regulate the power factor to control the reactive power, aiming to contribute to mitigate power quality problems in the power grid. To assess the behavior of the presented bidirectional power converter under different scenarios, are presented some computer simulations and experimental results obtained with a prototype that was developed to be integrated in an Electric Vehicle. Fundação para a Ciência e a Tecnologia (FCT) - FCOMP-01-0124-FEDER-022674, PTDC/EEAEEL/ 104569/2008, MIT-PT/EDAM-SMS/0030/2008. FEDER Funds, through the Operational Programme for Competitiveness Factors (COMPETE)

Abstract

This paper proposes a multi-control vehicle-to-grid charger with bi-directional power capability. The proposed charger can perform vehicle battery charging and discharging operations, as well as power grid support such as reactive power compensation, power factor correction, and grid voltage regulation. The performances of the charger controls were examined under various power grid scenarios. Results revealed that the vehicle-to-grid charger attained the highest charger efficiency when operating at unity power factor mode. Nevertheless, vehicle charging at unity power factor introduced a significant grid voltage drop which may violate the grid voltage limits. This problem was solved by using the voltage control, which injected reactive power to the power grid for accurate voltage regulation. This paper also proposed an autonomous multi-control selection algorithm to intelligently switch between the multiple charger controls in response to the power grid condition. Results showed that the proposed algorithm effectively instructed the charger to work in efficient control modes if the grid voltage was within the permissible voltage limits. Whenever the grid voltage exceeded the limits, the charger automatically switched to grid voltage control for power grid voltage regulation.