Harmonic currents control of three-phase four-wire grid-connected PWM inverter based on high-order repetitive controller

In this paper, a repetitive controller with the multi-rate system has been proposed to reduce harmonic currents from a grid-connected PWM boost converter with an LCL filter. The multi-rate system, where different sampling frequency coexists, makes it possible to reduce memory space requirement and computational burden of the repetitive controller. By exploiting the limited current regulation bandwidth due to the resonance of LCL filter, the signal for the repetitive controller can be decimated without any loss. By using decimation and interpolation, the memory space to keep the signals can be reduced conspicuously. In this paper, a technique reducing memory space and computational burden has been proposed and it was verified through a computer simulation and an experimental test. The experimental results show that there is no performance difference between conventional system and the system with the proposed technique. While, through the proposed technique, the memory space and the computational burden has been reduced by 64% and by 41%, respectively.