The Analytical Switching Modelling Method of Grid-Connected Converters for Transient Stability Analysis

In recent years, grid-connected power electronic converters have continuously rising influence on dynamics of bulk power systems, making modelling of power electronic converters critical to modern power system stability studies. However, few existing studies can systematically model the switching characteristics or handle discontinuous state variables of power electronic converters. To make up for the shortages, this article proposes a general four-step analytical switching modelling method of grid-connected converters: formulating holonomic differential-algebraic equations of the converter containing all switching actions, transforming all state-dependent switching conditions into time-dependent ones, deriving differential equations of the system in all time periods, and analyzing the continuity of each state variables at all switching moments. An example model is established and then evaluated by detailed simulations to verify the effectiveness of the proposed modelling method. Transient stability analysis based on the example model shows the practicality of the proposed method and the importance of considering switching characteristics in analytical modelling of power electronic converters.