Bidirectional embedded battery charger with V2G capabilities

Overview & Synopsis

Electric Vehicles (EV) are growing at a rapid pace in transport sectors because of increasing concerns on environment. Successful and rapid integration of EVs potentially reduce CO2 emissions. However, due to high penetration in the transport sector, EVs also represent substantial challenges for the Distribution System Operator (DSO). More specifically, the low-voltage grid operation becomes challenging due to sudden demand of energy as uncontrolled EV charging may coincides with the peak load demand. Thus, it results a severe voltage deviation, if energy systems are not managed in an organized way.Vehicle-to-Grid (V2G) is a technology, where EVs discharge their stored energy and inject that onto the grid during peak load period. Thus, it should not only be considered as passive loads but also energy sources while being in idle state. V2G technology also holds potential for providing ancillary services in energy sectors, such as, voltage regulation, voltage shaving, reactive power compensation and distributed generation. If managed properly, EV becomes an attractive asset for DSO. Thus, the battery charger of EVs should provide below functionalities:1. Charging of battery (Primary function): In this case, power is transferred from grid to vehicle, called G2V operation.2. Discharging of battery (Secondary function): In this case, storage unit of EV, i.e., battery is considered as energy source and power is transferred from vehicle to grid.3. Network balancing capability (Tertiary function): EVs can provide ancillary services to the grid, such as, reactive power or unbalance current consumption/injection for helping to balance and sustain the network without additional battery cycling.The first two functionalities had already been addressed by previous researchers (also in G2ELab by Dr. Mounir Marzouk). This thesis focuses on the mentioned third functionality that can be provided by EVs.These three functionalities necessitate the bidirectional battery charger for EV, which is capable of sinking or sourcing real and reactive power. Power Electronics part of the EV battery charger should combines AC/DC converter for maintaining near unity power factor of the grid and DC/DC converter for regulating battery current and voltage. One of the main objectives of the thesis is to compensate and mitigate unbalance active and reactive powers exchange between supplies of the 3-phases with the help of bidirectional EV battery charger. As the charger should also be onboard type, constraints are weight and volume for developing this type of charger.In this thesis, Neutral Point Clamp (NPC) converter and Triple Active Bridge (TAB) have been proposed and analyzed for AC/DC and DC/DC converter respectively. Objectives of this thesis have been analyzed and verified by the help of Matlab/Simulink results and Hardware-in-the-Loop (HIL) simulation results.