Design of Multi-loop Current Control Strategies for LCL Filtered Grid-connected PV System

Abstract

This paper presents numerous feedback current controller methods for the grid-connected PV systems incorporating with third order LCL filter. The various potential dual-loop feedback current controller schemes for a grid-tied electrical converter and a comparison among these controllers are made based on their performance. The effectiveness of these current controllers are based on various views like performance under polluted grid condition and also the dynamic performance of two control schemes under different transient conditions. A commonly used PI controller are employed in all cases of multi-loop controllers and also the electrical converter used here is operated in voltage control mode. In this work, a third-order low-pass LCL filter is employed to minimize the high order harmonics which are created due to the switching of the converter. The LCL filter is incorporated among the dc-ac converter and the utility grid. Two current regulation techniques are focused here. The design, analysis and the performance of these controllers are briefly discussed in this paper. By comparing their performance, anyone can suggest their applications in the grid-tied PV systems. All the current control schemes are incorporated with a grid-connected system of 2-KVA voltage source inverter. Simulation results are produced to validate the performances of two current control schemes. The output ohmic resistance of VSI is taken into account here for their performance analysis.