Two Dimensional Impedance Analysis of Grid-Connected Converter System: A Review

Renewable energy has developed vigorously in recent years. Due to the wide range of bandwidth involved in the renewable energy control, the interaction with the power grid has triggered a series of broadband oscillations. Considering that the control and structure of electronic devices are trade secret, the impedance method in frequency domain is often used. This paper summarizes the research in detail from two-dimensional impedance modeling and stability analysis of grid-connected converter system. Many scholars have tried to model under different coordinates, but due to the influence of asymmetric control, the system is always multi-input and multi-output (MIMO), which is difficult to realize the simultaneous decoupling of the renewable energy and grid side. Therefore, it is necessary to expand based on single-input and single-output (SISO) control analysis method and use multivariable frequency domain analysis method to analyze the open loop eigenvalue trajectories or closed loop system determinant. However, the extraction of MIMO system margin index and the guidance of impedance correction still need to be further studied.