Application of high-sampling-frequency control in low-switching-frequency Lcl-filtered system

In common LCL-filtered grid connected inverters, the sampling frequency will decrease in a low-switching frequency system, which will cause problems of current control. On one hand, the control delay will seriously influence the frequency response of system. And on the other, the effectiveness of active damping for LCL system will be challenged. To solve these problems, a method of applying high sampling frequency in the low-switching-frequency system is introduced in this paper. As high sampling frequency employed, control delay is reduced, and the effect on the design from low discrete frequency is minimized. In a 3kHz- switching-frequency LCL-filtered system with active damping and repetitive control involved, the controllers are design under 15kHz sampling frequency. Simulation and experimental results confirm the validity of the proposed method.