Voltage balancing control of a series-resonant DAB converter with a virtual line shaft

A multilevel series-resonant dual-active bridge (SRDAB) converter is widely used in high-voltage and high-power systems to reduce the voltage stress of inverter switches. However, an imbalance in the DC-link voltage between the DAB converters can cause system failure because inverter switches can be destroyed by voltage and current stress. In this study, a virtual line shaft (VLS) control is proposed to achieve output voltage and power balance between SRDAB converter modules. The gains of the controllers are selected using the frequency responses of the controllers. The disturbance rejection performance of the virtual line shaft and cross-coupling controller is compared. To evaluate the performance of the controllers, the time-domain responses of the VLS and cross-coupling controllers are compared. The simulated and experimental results show that the output voltages of the SRDAB modules are well balanced. The proposed voltage controller regulates the output voltage of an SRDAB module within 20 ms. The output voltages of the SRDAB modules are synchronized well even under asynchronous load changes.