Geometric analysis of grid-connected VSI with LCL-filter using Poincaré map

Abstract

Harvesting renewable energy sources is the key to solving the global energy crisis. The grid-connected voltage source inverter (VSI) is an essential part of the two-stage power conditioning system used to extract power from renewable energy systems and deliver it to the utility grid. Conventionally, an L-filter has been used to filter switching harmonics produced by the VSI. The LCL-filter, however, can provide effective filtering while using smaller components. When using the LCL-filter, it is necessary to provide active damping in the closed-loop system in order to damp the natural resonance of this third-order system. In this digest, the system is analyzed from a geometric viewpoint to see how the LCL-filter affects its stability. This geometric analysis entails finding the system flow and extracting the Poincare map in order to analyze the stability and behavioral characteristics of the grid-connected VSI with an LCL-filter. This analysis can supply insights into the system operation and controller design, which can prove useful for designing the closed-loop control system of the grid-connected VSI.