Optimization and Tradeoff of DC Bus Voltage Ripple and DAB Current Stress in Two-Stage Single-Phase Converter by Double-Line-Frequency Power Control

With consideration of double-line-frequency instantaneous power in two-stage single-phase system, a double-line-frequency power control method is proposed in this article to achieve optimization and tradeoff control between the current stress of dual-active-bridge (DAB) dc/dc converter and the dc bus voltage ripples in both sides. Different double-line-frequency powers in DAB will lead to different values of DAB current stress and dc bus voltage ripples in both sides. To find out the best double-line-frequency power in DAB, the optimal control trajectory (OCT) is proposed in this article so that the current stress of DAB can be minimized under any certain voltage ripple. An approximate analytical calculation method is derived to solve the optimal double-line-frequency power in OCT. The comparative analysis indicates that the approximate OCT has similar optimization effects as OCT. Based on the OCT, two tradeoff control methods for the DAB current stress and the dc bus voltage ripples are presented so that the current stress and the voltage ripples can be flexibly adjusted to adapt various load conditions. The initial phase of the single-phase ac load is also optimized to maximize the adjustable range of voltage ripple. The experimental results verify the feasibility and effectiveness of the proposed OCT and control methods.