Adaptive proportional resonant controller for single-phase grid-connected PV inverter based on grid impedance estimation technique

Abstract

Photovoltaic PV systems have shown a significant growth in recent years driven by the increased efficiency and reductions in the cost of PV modules. Today, distribution generation based PV systems have a major contribution to the total electricity production worldwide. However, in areas with high penetration of PV system connected to the grid, interaction may arise between the grid and PV system. This research focuses on the effect of grid operating conditions on the performance of grid-connected PV inverter systems. A simulation model of the system under investigation has been developed to evaluate the impact of frequency deviation, grid voltage distortion and grid impedance variation on the harmonic performance of the injected current as well as the voltage at the point of the common coupler. Proportional resonance PR controller is employed to regulate the current produced from the PV inverter due to its reputation in tracking sinusoidal signals. The obtained simulation results demonstrate that the harmonic performance of the grid current and PCC voltage can be significantly influenced by the change of grid operating conditions. In particular, grid impedance variation can result in a shift in the system resonance frequency leading to distortion in network current and voltage. To adapt the PR controller to the grid impedance variation, a novel adaptive PR controller which takes into account the change in grid impedance is proposed. The adaptive consists of a high-order digital band-pass filter and chain of statistical signal processing technique. Simulation results show that the harmonic performance of grid current and PCC voltage can be enhanced and the proposed APR controller is robust against impedance variation. Finally, the proposed control method is experimentally implemented and the obtained results validate the effectiveness of the proposed control structure.