An MPC-controlled Bidirectional Battery Charger with DC-DC and Three-level F-type Converters

This paper proposes a single-phase bidirectional battery charger which comprises a three-level F-type converter and a bidirectional dc-dc converter. The proposed charger is suitable for electric vehicles and battery energy storage systems. The bidirectional dc-dc converter is integrated into the system to prevent the charge current oscillations caused by double-line frequency voltage ripples of the F-type converter when operates as a single-phase rectifier. The F-type converter operates as rectifier and inverter during charging and discharging modes, respectively. The power flow of the battery is controlled with a bidirectional dc-dc converter. The current control of both F-type and bidirectional dc-dc converters is achieved by the model predictive control (MPC) method. The control strategy is designed by considering the power balance theory. For this purpose, the voltage of the common connection point of both converters (dc-link) is regulated. The grid current reference of the F-type converter is obtained by using a proportional-integral (PI) controller whose input is the dc-link voltage error. Thus, bidirectional power flow control is achieved. The effectiveness of the proposed power converter structure as well as the control strategy is investigated by simulation studies performed on MATLAB/Simulink environments. The results show that the proposed system is capable of controlling the grid and battery currents in both power directions.