V. CONCLUSION
This paper proposes a PSO-Optimized Phase-Shift control (POPS) based on the unified phasor analysis with aim to minimize the reactive power and improve the efficiency of the bidirectional dual active bridge (DAB) converter for the whole operation range. Firstly, through building a unified mathematical model based on Fourier transform for the DAB converter, accurate complex mathematic expressions for the inductor current, the transmission power and the reactive power are obtained. Then, the unified-phasor-based PSO is adopted to directly determine the optimal phase-shift variables in minimizing the reactive power under 3-level modulated phase shift control without a cumbersome process of the optimal operation mode selection. Main analysis and experimental results are provided for different voltage conversion ratio and load conditions. Various modes, including forward mode, reverse mode, buck mode and boost mode, are also analyzed. The results show that the proposed POPS can successfully minimize the reactive power and maintain a high maximum transmission power especially in the high voltage conversion and light load condition. Furthermore, the ZVS region is extended using POPS, which can reduce switching loss. Specifically, with the proposed POPS algorithm, the measured maximum efficiency under the rated load is improved by 3% and the efficiency improvement under the light-load condition is high up to 9%. The dynamic test result under the load changing condition validate the correct operation of the output voltage closed-loop control and fast dynamic response of the proposed POPS algorithm.
