The invention relates to the technical field of grid-connected 
inverter control, and relates to a fractional 
phase compensation control method and device for an LCL grid-connected 
inverter under a weak 
power grid. The method comprises the steps: 1, respectively obtaining a 
voltage signal and a grid-connected current 
signal; 2, extracting 
voltage phase angle information; and generating a grid-connected current reference 
signal in the 
control system; 3, dividing the obtained grid-connected current signal into two paths, feeding back an inherent 
harmonic peak of an active damping suppression LCL grid-connected 
inverter through the grid-connected current, obtaining an 
error signal by subtracting the other path from the grid-connected current reference signal, and transmitting the 
error signal to a current controller for modulation; 4, after the 
error signal is modulated by a current controller, subtracting the error signal from a grid-connected current feedback active damping signal to obtain a modulated wave signal; and 5, comparing to obtain a 
control signal. The current controller structure is a proportional 
resonance parallel 
repetitive control structure with a fractional 
phase compensation function, the design is simple, and flexible fractional 
phase compensation can be provided under a weak 
power grid.