Frequency-Adaptive Virtual Variable Sampling-Based Selective Harmonic Repetitive Control of Power Inverters

Abstract

Due to the n-pulse commutation, the power harmonic distortions caused by power inverters usually concentrate on particular (nk±m)-order harmonic frequencies. The conventional repetitive control (RC) uses an identical gain to equally compensate for the distortions at all harmonic frequencies. This leads to slow dynamics as it fails to optimize the convergence rate of the RC at dominant harmonic frequencies. The selective harmonic RC (SHRC) can efficiently suppress dominant power harmonic distortions. However, the ratio of the sampling rate of the SHRC to the fundamental frequency must be an integer. This severely limits the use and lowers the performance of the SHRC with a fixed sampling rate in the presence of frequency variations of interested harmonics. To address this problem, this article proposes a frequency-adaptive virtual variable sampling-based SHRC (FA-VVS-SHRC) scheme that is immune to the issue of the fractional ratio of the sampling rate to the interested harmonics. The proposed FA-VVS-SHRC scheme can provide flexible fractional phase-led compensation to achieve accurate power harmonic control in the presence of frequency variations. Moreover, it is a low-cost and easy-to-implement solution that does not require hardware modifications. Experiments on a three-phase power inverter and comparison studies are presented to verify its effectiveness.