Impact of Digital Control Delay on Stability of Grid-Following Converters

In a digital controlled system, the delay is inevitable. It will change the phase-frequency characteristics of the system, which will affect the stability. This paper analyzes the configuration of the grid-following converter and builds its small-signal model in detail. The impacts of delay on the stability of grid-following converters are analyzed through impedance-based model and single-input single-output (SISO) transfer function. In order to achieve a fair comparison, the two stability analysis methods are applied to the same system. Finally, a time-domain simulation model of 7 kW grid-following converter is built in Matlab/Simulink and an experimental prototype with same parameters is carried out to verify the effectiveness of the theoretical analysis.