A New Grid Side Inertia Support Control Method for Cascaded Power Converters in Bi-directional EV Chargers

In order to provide extra power when grid frequency fluctuates, the bidirectional EV charger has used the virtual synchronous generator (VSG) control in its grid-side DC/AC converter. However, the existing VSG control cannot actually realize the inertia support due to the limitations of the existing cascaded power converters control structure of the EV charger. This paper proposes a power feedforward control to instantaneously track the inertial supporting surge power by DC/DC so as to stabilize the DC bus voltage. Meanwhile, the droop coefficient based power feedback is also fed forward to DC/DC controls to support grid frequency control with larger time scale. Finally, the advantages of the proposed control structure over the conventional one were verified via simulation models.