Novel Voltage Balancing Control Strategy for Dual-Active-Bridge Input-Series-Output-Parallel DC-DC Converters

This paper proposes a novel input voltage balancing control strategy for dual-active-bridge (DAB) input-series-output-parallel (ISOP) DC-DC converters. The proposed strategy not only aims at balancing the input voltage among modules but also at eliminating the coupling effect between input voltage sharing regulators (IVSR) and output voltage regulators (OVR). Specifically, this paper reveals it is too complicated to design a decoupling control structure that can eliminate the dynamic interference of IVSRs to OVRs by using traditional control strategies. Thus, an intermediate control variable, which was adjusted by the IVSR and OVR to simplify the decoupling control structure design, was introduced to calculate the phase-shift ratio. Furthermore, a new control law was derived, and an expression for the intermediate control variable modification was proposed to achieve decoupling control. Moreover, to complete the discussion, the main transfer functions were deduced and the design procedure was illustrated. Based on the novel control strategy, the interference of an IVSR to an OVR was eliminated, so the two controllers can be independently designed. Finally, both the simulation and experimental results were used to verify the performance of the novel control strategy.