Aiming at the problem of low efficiency under port voltage mismatch and light load of triple active bridge (TAB) isolated bi-directional DC-DC converter

this paper establishes an accurate unified mathematical model of TAB based on Fourier series

and proposes a multiple phase-shifting angle closed-loop optimization control strategy that can simultaneously achieve the optimal RMS value of the inductor current and zero-voltage switching (ZVS) in the full power range. To avoid the cumbersome computational process introduced by the segmented linearization method

the multi-objective function is solved globally by the gradient descent algorithm. The optimal operating points are subjected to polynomial curve fitting to ensure that the phase shift angle and the transmission power are continuously varied and can be smoothly switched between different modes. Simulation and experimental results show that compared with other control strategies

the proposed optimization strategy can significantly reduce the conduction loss and switching loss. The light-load efficiency can reach up to 96%

and it is effective under different mismatch ratios.