Control Strategy for Bidirectional DC-DC Converter Based on Cascade Connection of LC Filter and DAB Converter

The dual active bridge (DAB) DC-DC converter has broad prospects for use, for example, energy-storage systems, electric vehicles, and DC distribution network. To improve the quality of bus current, researchers often cascade filter inductors to the DC port of DAB converter. If so, the system may be instable and oscillate because the converter is turned into a cascaded structure of LC filter and DAB converter. In addition, it is found that the output current is used as the feedback variable for closed-loop control in bidirectional transmission, which will increase the number of sensors. And, the current of the energy storage unit (ESU) cannot be directly controlled when the ESU discharges. To solve these problem, this paper proposes a control strategy based on notch filter (NF) regulator. Regardless of whether power flows in the forward or reverse direction, the filter inductor current is always regarded as control objectives. For this purpose, NF regulator is introduced into the forward path of the current loop to suppress the oscillation of the LC filter inductor current. Finally, the effectiveness of the theoretical analysis and proposed strategy are verified by simulations and experiments.