Research on an Extended Phase-Shift Control Strategy of an Electric Vehicle Auxiliary Power Module with an Equalization Function

In the field of new-energy electric vehicles, lithium battery cells need to be connected in series and parallel to meet the requirements of high voltage and high power. Aiming at the high cost of traditional active equalizer, a half/full-bridge converter is developed, which integrates lithium battery equalization technology into the auxiliary power module of an electric vehicle. The asymmetric modulation strategy is realized by introducing DC duty ratio adjustment at the half-bridge side to improve the balancing speed. In order to suppress the backflow power of the whole bridge side, an extended phase-shift control strategy is proposed based on the single-phase-shift control strategy. The working principle and mode of the half/full-bridge converter under the proposed control strategy are analyzed, and the mathematical models of transmission power and reflux power of the converter under the two control strategies are compared. The experiments show that the modular half/full-bridge converter functions using lithium battery equalization and an auxiliary power module; they also verify the correctness of the proposed extended phase-shift control strategy.