Bidirectional Power Transfer between Grid and Electric Vehicle Batteries

Abstract

In the last decades, the significant growth of electric vehicle (EV) is promising an alternative to solve the concern about fossil fuel and global warming. However, as the number of EVs increasing significantly, it can cause overload in the existing distribution network of the power system. The vehicleto-grid (V2G) technology is recognized as the best alternative to mitigate the stress in the electric grid by providing ancillary service and power balancing in the power system. The tasks covered in this thesis are: Different effective ways of EV charging are reviewed, and their advantage and disadvantages are addressed. A literature review of common bidirectional AC-DC and DC-DC converters are carried out. Several converter topologies can be used to implement the bidirectional EV chargers. It is found that the two-level three-phase AC-DC converter and either half-bridge buck/boost for a non-isolated converter or a dual active bridge for an isolated converter in DC-DC converter are leading topologies. For safe and reliable power transfer between EV and the grid bidirectionally, the available bidirectional charging standard is investigated. Right now, the only bidirectional charger accepted as standard is the CHAdeMO with DC charging. Finally, a two-stage bidirectional EV charger with and without galvanic isolation is developed and simulated in MATLAB/Simulink. The first stage is a three-phase AC-DC converter, and the second stage is modeled with both half-bridge non-isolated DC-DC converter and dual active bridge isolated DC-DC converter. All the converters transfer power bidirectionally. The simulation results showed that the two-way power transfer with the proposed bidirectional EV charging station models is feasible.