Influence and Suppression Control Strategy of DC Voltage Ripple on Single-Phase Back-to-Back Three-level Converter

For the existing problem of large dc-link capac-itance of single-phase back-to-back converter in the co-phase power supply system, this paper proposes a control strategy to suppress the influence of dc-link voltage ripple with reduced dc-link capacitor. The proposed control strategy introduces specific-order harmonic currents control to suppress the influence of voltage ripple on the three-phase power quality based on the traditional dq decoupling control. The expression of the dc-link voltage based on the co-phase traction power supply system with YNvd transformer is derived, and the minimum value of dc-link capacitance is calculated within the acceptable ripple. The simulation results show that the proposed control strategy can reduce the dc-link capacitance by about 80% compared with the traditional control strategy under the same performance of three-phase grid.