Abstract:

The distortion of background harmonic voltage is inevitable in grid-connected system, which would result in serious low-order harmonics in the injected grid current. The low-order harmonics can be suppressed by increasing the switching frequency, while it also brings many high-order harmonics. Based on PR+HC-based current controller, the effects of the current controller parameters on steady-state error, phase margin and gain margin in LCL-type grid-connected inverter are investigated. A method is given to obtain the controller parameters’ region that meets the requirements, and the optimal parameters could be obtained on the basis of analysis in system stability. Simulation results verify the proposed control scheme and parameters design method.

Key words: grid-connected inverter; proportional-resonant control; harmonic compensation; LCL filter