Analysis of the Stability and System Participation Factors of Grid-Connected Converters

When the sources of renewable energy and numerous power electronic gadgets are introduced into the power system, which is related to the negative resistance features of power electronic gadgets, the power system with high power electronics often exhibits weak inertia. Also the stability of multi-converter grid-connected systems is adversely affected. To address these issues, a process of small disturbance stability analysis is proposed in this paper for the grid-connected systems of multiple grid-forming converters based on impedance ratio criterion. The Nyquist trajectory map of the system ratio of impedance in the complex plane is used in the suggested analytical method to estimate the quantity of RHPs in the right half-plane of the system, and the stability at the common points of the system is evaluated against the Nyquist criterion. In addition, the instability of grid-forming converters in grid-connected systems is reproduced by using grid-forming converters state space equation. Unlike the traditional methods of analysis, the method proposed in this paper can be applied to specifically judge the key equipment or control link of instability of the system, which provides guidance on optimizing the parameters of the system. Finally, simulation analysis is conducted to confirm that the model is accurate and that the proposed approach is applicable.