Damp and droop coefficient stability region analysis for interlinking converters with virtual asynchronous machine controllers in virtual energy storage systems

Although virtual energy storage systems (VESSs) based on virtual asynchronous machine (VAM) control strategy have been widely applied to microgrids to achieve power balance between supply and demand sides, damp and droop coefficients are variable due to the system operation state. It is prone to causing wideband oscillation, such as low-frequency and sub/super-synchronous oscillation. Thus, this paper proposes one damp and droop coefficient stability region identification approach based on the Guardian map theory for the interlinking converter (IC) of VESSs. Firstly, the VAM control method of IC is derived through the traditional asynchronous machine, and its small-signal model is further built. The aforesaid process is the important modeling basic. Secondly, the concept of the practical small signal stability region (P-SSSR) is proposed to make up for the deficiency of the traditional small signal stability region (SSSR) that cannot ensure system robustness. Thirdly, the mapping method based on translation and rotation mapping is introduced to ensure that the identification of the P-SSSR problem is switched into the Hurwitz matrix identification problem. Furthermore, the high-dimensional parameter stability region can be obtained through the Guardian map theory. Finally, the performance of the proposed method can be verified through simulation and experiment results.