Control and modulation of a family of bidirectional AC-DC converters with active power compensation

In a single-phase grid-connected nanogrid system, a bidirectional AC-DC converter is usually required to transfer energy between the AC grid and a DC bus. However, a ripple power at twice the grid frequency may be injected from the AC grid into the DC bus if the ripple power is not properly compensated. In this paper, a family of bidirectional single-phase AC-DC three-phase-leg PWM converters for use in the nanogrid system is analyzed. The averaged DC power and the second-order AC power of the AC grid are actively decoupled. A proper AC voltage reference for AC power compensation is analyzed and selected for the charge storage capacitor for better efficiency. A generalized control structure is proposed for the family of converters. Applying modulation with extra zero-sequence voltage injection derived from the three-phase-leg PWM voltages, a significant reduction of the AC storage capacitance is achieved and the converter efficiency is also improved. Finally, the analysis is verified by simulations and experimental measurements.Department of Electronic and Information EngineeringRefereed conference pape