Research On Multi-port Converter Based Infrustructure For Integration Of Electric Vehicle (EV) Into Grid

Vigorously developing the clean-energy vehicles, especially Electric Vehicles(EVs), has become a strategic option all over the world to alleviate the energy crisis and environmental pollution.The duality as "Load" and "Source" makes the EV be an essential part in establishing the Energy Internet in the near future. On the one hand, the large-scale usage of EVs will bring the congestion problem to the utility because of the rapid increase and uncertainty of charging loads, while on the other hand, the large-scale EV fleets can be considered as mobile energy storage systems (MESS) by virtue of the on-board batteries the EVs equipped and the MESS may provide some ancillary service, such as spinning reserve, voltage/frequency support or fault ride-through capability for the utility. However, the advantages the EVs depends on the high-efficiency grid-integration ways of EVs, though the charger topologies are various, the main grid-integration infrustructure of the EVs are those integrating the EVs to the AC or DC bus in parallel via the chargers in the present application. But these infrustructure have the following disadvantages: 1) Each charger can only charge one EV at the same time, which makes the land utilization efficiency of the charging station be low and extra chargers need to be installed with the EVs increases; 2) Communication units need to be equipped to control the EVs charging/discharging in coordination; 3) There are many power conversion stages and switches in the integration system and individual control system is needed for each EV charger, which makes the construct cost of the charging station be high.The motivation of this thesis is to study multi-port converter based infrustructure for integration of electric vehicle into grid which has advantages including compact structure, less power conversion stages, allow multi EVs charging/discharging using one charger, and enables integration of renewable energy power generation units into grid efficiently, bi-directional power flow between the EVs and the utility along with centralized control to provide an alternative novel EV integration structure, and the detail context of this thesis is organized as follows:1. A detailed overview on the EVs integration into utility is present with the perspectives of research background, EV charger topologies, the existing EV integration structures and the interaction techniques research between EVs and the utility. In addition, the multi-port converter topologies in the presented literature are classified and some application is introduced as well as the general control method is analyzed.2. The detail analysis on the three types of present EV integration infrustructure are carried out and their respective characteristics are summarized. Then the DC-bus based integration infrustructure is taken as the example, its concrete structure, control objectives and control strategy in detail are introduced respectively, then the simulation is performed in Matlab/Simulink to present it more intuitive.3. A novel EV integration proposal based on the multi-port converter is proposed in this thesis. Two specific MPC-based EV integration topologies are studied, one is non-isolated MPC based on bi-directional Buck-Boost converter, the other one is isolated MPC based on magnetic coupling. The topology structures, operating principle and control strategies of the two integration topologies are both introduced taking the three-port topology as the example. Simulation models are established in Matlab/Simulink and the results verify the feasibility and effectiveness of the proposed integration topology.