Single-Phase Grid-Connected Inverter Parameter Sensitivity Analysis using Wide-band Impedance Estimations

The growing integration of renewable energy resources has led to an increasing number of grid-connected inverters, introducing challenges to grid stability and power quality. Impedance-based methods are commonly used to assess the harmonic stability of these systems. This paper investigates how grid parameters, inverter filters, and controller settings influence the wide-band impedance response of a grid-inverter system. A single-phase grid-connected inverter, incorporating a current controller and phase-locked loop (PLL), is modelled. The system’s impedance response is analyzed using wide-band excitation at the point of common coupling (PCC) to estimate the grid and inverter’s frequency-dependent impedance. Simulation results demonstrate the significant impact of controller gains on the impedance response, highlighting that the impedance is not solely defined by passive components but also depends on the dynamic interaction between voltage and current. This study provides valuable insights into the stability of grid-connected inverters, offering a foundation for designing robust systems and enhancing renewable energy integration into modern power grids.