A novel control scheme for bi-directional Buck Boost converter

In this paper, the DC bus voltage fluctuation suppression in the motor drive system with bi-directional Buck / Boost converter is studied. The disadvantage that power feed-forward control scheme cannot effectively suppress bus voltage fluctuations is analyzed. A novel direct power control scheme with bus capacitor energy outer control loop and output power inner control loop for the bi-directional Buck/Boost converter is presented. Moreover, in order to improve the dynamic response of converter,a feed-forward term which reflects the changing trends of output power is added on its duty cycle calculation node. The essential difference between the above two control schemes is compared. Small-signal model analysis results and simulation and experimental results show the direct power control scheme has better performance in voltage fluctuation suppression.