A new control strategy for bi-directional DC-DC converter in electric vehicle

In order to improve the drive system efficiency, a boost/buck bi-directional DC-DC converter which can regulate the DC-link voltage according to optimal efficiency curve is added between the battery and the traditional voltage source inverters (VSI) supplying a motor. The traditional control approach for the bi-directional DC-DC converter is based on the analog control concept. However, it is not the best choice in digital control environment. In this paper, a new control strategy with a digital control concept is presented which can achieve a smooth switching between the boost and buck operation state using only one controller. The small-signal model of the controller is built and the relationship between the out power and the DC-link voltage stability is discussed. The PMSM drive system in electric vehicles (EV) is modeled using MATLAB/simulink and a operation condition in EV is simulated to verify the above theoretical analysis. The simulation and theoretical analysis results match with good agreement.