RT22 | Control Design for V2G-enable DC charging station with controller-hardware-in-loop (C-HIL)

In this study, a control design for the usage of electric vehicles in vehicle-to-grid (V2G)-enabled DC charging stations is proposed. The V2G-enabled DC fast charging station is equipped with bidirectional DC/DC converters for each electric vehicle charge and the installed energy storage system, and a three-phase two-level voltage source converter for connecting to the low voltage grid. The proposed control design uses each EV battery's energy capacity, state-of-charge, and current limits when allocating power among electric vehicles in V2G mode and the energy storage system to limit the power from the grid. In the proposed controller, the electric vehicles' energy capacities and state of charges are the allocation factors, and the current limits are the limiting boundaries. The proposed control design ensures a safe operating range for electric vehicles while using electric vehicles efficiently. The proposed state-of-charge balancing algorithm integrated into the proposed controller ensures the efficient usage of electric vehicles in V2G mode. Offline simulation and controller-hardware-in-loop (C-HIL) evaluate the performance of the proposed controller for validation. The C-HIL implementation provides cost-effective, safe, and fast validation results of the primary controller of the V2G enable-DC charging station on real-world industrial hardware. In the C-HIL, a digital signal controller (DSC), a TMS320F28379D DSP controller is the controller hardware, and a real-time simulator, OPAL-RT OP5600 simulates the DC charging station model in real-time. Modeling the charging station in the OPAL-RT prevents violating the electric vehicle batteries' safe operating zone during validation studies, which could cause hazards and safety issues. The DSC and real-time simulator communicate through Digital and analog input/outputs. The DSC sends the control signals via digital outputs, and the real-time simulator sends the voltage and current measurement signals via analog outputs. The C-HIL case studies include three case scenarios. The first case scenario studies the steady-state performance of the proposed V2G controller when the grid power is limited and can change during the simulation time. The second case scenario focuses on the transient response of the proposed controller when changing the EV battery current limit due to specific battery conditions. Finally, the third case scenario discusses the performance of the proposed controller to the mode changing of an electric vehicle from the V2G mode to the fast charging mode. In all case scenarios, the offline simulation and C-HIL results match closely and validate the robust and efficient performance of the proposed controller