Decoupling Control of Triple Active Bridge-Power Flow Controller in Meshed Bipolar DC Distribution Grids

Due to the lack of freedom in power flow (PF) control of the meshed bipolar dc distribution grid, the PF of some lines becomes uncontrollable. Besides, there is a coupling between the poles due to the unbalanced current and line resistance, which may deteriorate the dynamic performance of the control system. To solve the above problems, this article proposes an unbalanced PF regulation methodology based on a triple active bridge-power flow controller (TAB-PFC) and studies the decoupling control of TAB-PFC. This article analyzes the influence of receiving-end voltage on positive and negative PF and line losses. The expressions of output voltage and line current of TAB-PFC under constant power control are also derived, and the small-signal model of a meshed bipolar dc distribution grid with TAB-PFC is established. On this basis, the decoupling matrix is introduced between the positive and negative control loops to improve the dynamic performance of the control system. A simulation model of meshed bipolar dc distribution grid with TAB-PFC is established in MATLAB/Simulink, and an experimental platform is built. The simulation and experimental results verify the effectiveness of TAB-PFC in restraining unbalanced PF and the effectiveness of the decoupling matrix.