Impact of Additional Proportional Resonant Control on Impedance Characteristics and Broadband Oscillation of Grid-Connected Converters

The proportional resonant (PR) controllers are widely used by manufacturers in combination with conventional current-loop PI control to mitigate the 5th and 7th harmonics in grid-connected converters. However, the superimposition of the additional PR control may deeply change the impedance characteristics of the converter and bring new risk of broadband oscillation in converter-dominated systems. In this paper, the impedance model considering the additional PR control of a grid-connected converter is established and verified using the multi-harmonic linearization method. Based on the analytical model, the impact of the additional PR control on the impedance characteristics and broadband oscillation of grid-connected converter is analyzed, the optimized parameter design strategy to eliminate negative damping is presented. Finally, based on the control hardware in the loop simulation platform, experiments were conducted, verifying the correctness of the analysis in this paper.