Reduced Model of Droop-controlled Converters for Transient Simulation Analysis

In recent years, the transient stability problems encountered by power grids have increasingly attracted interest due to the connection of renewable energy resources. One of the effective methods for studying the transient characteristics of a system is transient simulation analysis. To reduce the simulation time, especially in a system with numerous renewable energy resources, model reduction has been widely employed. However, when a general reduced model is adopted to analyze different transient characteristics, a tradeoff between accuracy and simulation speed emerges. In this study, reduced model selection is implemented to resolve this problem. Considering the droop-controlled converter as an example, this approach allows the transient simulation analysis of voltage, frequency, and power angle characteristics. First, a full-order model of the droop-controlled inverter is formulated. Thereafter, the singular perturbation method is applied to derive different reduced-order models. Then, considering accuracy and simulation speed simultaneously, the most suitable reduced models for transient angle, voltage, and frequency simulation analyses are determined through time-domain simulation comparison. Finally, the simulation results based on Matlab/Simulink are used to verify the correctness of the reduced model selection.