Direct power ripple rejection of grid-connect inverter under harmonically distorted voltage conditions

A certain 5th and 7th harmonic voltage in the grid is allowed, which will result in 6 times output power ripple of the grid-connected inverter based on the traditional vector control. In order to enhance adaptive ability for grid-connected inverter, a direct power ripple rejection strategy based on resonant controller is proposed in this paper to achieve smooth output active power and reactive power. Another power pulsation compensation loop, with traditional voltage oriented vector control remained, is added to achieve the control of the active and reactive current and the power pulse component of the grid-connected inverter. The control system can directly suppress the output active and reactive power fluctuation and improve the system dynamic and static performance without phase decomposition of harmonic current and voltage. The adopted strategy is finally verified by simulation results.