Adaptive current control strategy for harmonic compensation in single-phase solar inverters

Abstract Nowadays, the power systems are submitted to current and voltage harmonics due to the increased presence of nonlinear loads and the wide use of power inverters to interface solar and wind power plants. Nevertheless, these inverters can also be used to compensate the current harmonics. Traditional harmonic detection methods extracts all harmonic current information and the control tuning tends to be complex and less flexible. Therefore, this work proposes an adaptive current harmonic control strategy applied in multifunctional single-phase solar inverters. The strategy is based on a novel detection method of the harmonic load current. The harmonic current detection method is frequency adaptive and designed to extract the load harmonic current with higher amplitude. The detected harmonic is compensated using an adaptive proportional resonant (PR) controller, reducing the grid current total harmonic distortion (THD). The detection method consists of two-cascaded phase-locked loop based on second order generalized integrator (SOGI-PLL) which uses the detected frequency to automatically tune the PR. The proposed method is explored in terms of nondetection zone, the impact of the SOGI-PLL parameters and the control stability analysis. Simulation and experimental results show the performance of the proposed control strategy, reducing significantly the grid current distortion.