Stability Analysis of Grid-connected Converters with Add-on Voltage Support Functionality using Repetitive Control

The aim of this paper is to analyse the stability of grid-connected converters using repetitive control for voltage harmonic compensation. Supplementary to an earlier proposed control strategy to upgrade grid-connected converters for add-on voltage support, the stability analysis of the overall system is presented. A straightforward procedure is proposed and a couple of stability conditions are derived. The analysis is broken down into two sub-parts and therefore, the Nyquist's criterion can be easily applied. Simulations and experiments support the stability model analysis. The proposed method is not limited to the application with voltage support but also applicable for other converter systems based on repetitive-control algorithms.