Impedance Characteristics and Harmonic Analysis of LCL-Type Grid-Connected Converter Cluster

Abstract

This study addresses the output impedance model of the LCL-type grid-connected converter considering the dead-time effects and the digital control delay. The model shows that the digital control delay will affect the accuracy of the output impedance of the grid-connected converter, and the dead-time effects are only equivalent to superimposing a disturbance voltage on the original output impedance model. The derived output impedance model is verified by comparing it with the switching model in the PSIM simulation environment. The harmonic interaction between converter cluster and utility grid is modeled and analyzed based on the output impedance model. A combined harmonic suppression strategy is incorporated into every converter control scheme to suppress the harmonic interaction. Simulation results are presented to demonstrate the correctness of harmonic interaction analysis and the effectiveness of the proposed suppression strategy.

Coordinated Mitigation Control for Wideband Harmonic of the Photovoltaic Grid-Connected Inverter

“…LCL filters with small sizes and high-frequency attenuation capability are widely used to effectively mitigate the poor power quality of grid-connected inverters. As a high-order filter, the LCL filter has inherent resonance points [16]. The following two categories comprise the research on resonance suppression of grid-connected inverters.…”