Reduced-Order Symbolic Admittance Model and Stability Analysis of Grid-Following Converters

In recent years, the penetration of power electronic devices in the power system becomes higher. Grid-following converter, as a main category of renewable energy interface in the power grid, may trigger stability problems under some circumstances. However, with the increasing complexity of control strategy and grid structure, stability analysis becomes a difficult task due to the heavy computational burden and vague physical meaning of the high-order small-signal model. Numerical order reduction methods cannot offer clear physical interpretation, and existing symbolic simplified models cannot cover a wide frequency band. To fill this gap, a reduced-order symbolic admittance model is proposed in this paper using bode diagram curve analysis and control loop decoupling, which is accurate in a wide frequency band (1~5000Hz). Based on this model, the corresponding RLC circuit model is subsequently constructed. At last, simulation and experimental results validate the effectiveness of the model.