Improved Current Controller Based on SVPWM for Three-phase Grid-connected Voltage Source Inverters

Space vector pulse-width modulation (SVPWM) has been widely employed for the current control of three-phase voltage source inverters (VSI). However, in grid-connected distributed generation (DG) systems, SVPWM also brings drawbacks to current controllers, such as the compromised output current due to the grid harmonic disturbance and nonlinearity of the system, the lack of inherent over-current protection, etc. In this paper, an improved current controller has been developed for three-phase grid-connected VSIs. A grid harmonic feed-forward compensation method is employed to depress the grid disturbance. Based on a dual-timer sampling scheme, a software predictor and filter is proposed for both the current feedback loop and grid voltage feed-forward loop to eliminate the system nonlinearity due to the control delay. Both simulation and experimental results have verified the superior performance of the proposed current controller